Revision: 1017
http://www.exim.org/viewvc/pcre2?view=rev&revision=1017
Author: ph10
Date: 2018-09-21 17:59:48 +0100 (Fri, 21 Sep 2018)
Log Message:
-----------
Implement PCRE2_EXTRA_ESCAPED_CR_IS_LF
Modified Paths:
--------------
code/trunk/ChangeLog
code/trunk/doc/html/pcre2_set_compile_extra_options.html
code/trunk/doc/html/pcre2api.html
code/trunk/doc/html/pcre2pattern.html
code/trunk/doc/html/pcre2test.html
code/trunk/doc/pcre2.txt
code/trunk/doc/pcre2_set_compile_extra_options.3
code/trunk/doc/pcre2api.3
code/trunk/doc/pcre2pattern.3
code/trunk/doc/pcre2test.1
code/trunk/doc/pcre2test.txt
code/trunk/src/pcre2.h.in
code/trunk/src/pcre2_compile.c
code/trunk/src/pcre2test.c
code/trunk/testdata/testinput2
code/trunk/testdata/testoutput2
Modified: code/trunk/ChangeLog
===================================================================
--- code/trunk/ChangeLog 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/ChangeLog 2018-09-21 16:59:48 UTC (rev 1017)
@@ -20,7 +20,9 @@
5. Fix an xclass matching issue in JIT.
+6. Implement PCRE2_EXTRA_ESCAPED_CR_IS_LF (see Bugzilla 2315).
+
Version 10.32 10-September-2018
-------------------------------
Modified: code/trunk/doc/html/pcre2_set_compile_extra_options.html
===================================================================
--- code/trunk/doc/html/pcre2_set_compile_extra_options.html 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/html/pcre2_set_compile_extra_options.html 2018-09-21 16:59:48 UTC (rev 1017)
@@ -32,6 +32,7 @@
<pre>
PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES Allow \x{df800} to \x{dfff} in UTF-8 and UTF-32 modes
PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL Treat all invalid escapes as a literal following character
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF Interpret \r as \n
PCRE2_EXTRA_MATCH_LINE Pattern matches whole lines
PCRE2_EXTRA_MATCH_WORD Pattern matches "words"
</pre>
Modified: code/trunk/doc/html/pcre2api.html
===================================================================
--- code/trunk/doc/html/pcre2api.html 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/html/pcre2api.html 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1873,6 +1873,14 @@
that typos in patterns may go undetected and have unexpected results. This is a
dangerous option. Use with care.
<pre>
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF
+</pre>
+There are some legacy applications where the escape sequence \r in a pattern
+is expected to match a newline. If this option is set, \r in a pattern is
+converted to \n so that it matches a LF (linefeed) instead of a CR (carriage
+return) character. The option does not affect a literal CR in the pattern, nor
+does it affect CR specified as an explicit code point such as \x{0D}.
+<pre>
PCRE2_EXTRA_MATCH_LINE
</pre>
This option is provided for use by the <b>-x</b> option of <b>pcre2grep</b>. It
@@ -3724,7 +3732,7 @@
</P>
<br><a name="SEC42" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 18 September 2018
+Last updated: 21 September 2018
<br>
Copyright © 1997-2018 University of Cambridge.
<br>
Modified: code/trunk/doc/html/pcre2pattern.html
===================================================================
--- code/trunk/doc/html/pcre2pattern.html 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/html/pcre2pattern.html 2018-09-21 16:59:48 UTC (rev 1017)
@@ -393,7 +393,7 @@
\e escape (hex 1B)
\f form feed (hex 0C)
\n linefeed (hex 0A)
- \r carriage return (hex 0D)
+ \r carriage return (hex 0D) (but see below)
\t tab (hex 09)
\0dd character with octal code 0dd
\ddd character with octal code ddd, or backreference
@@ -403,6 +403,12 @@
\N{U+hhh..} character with Unicode hex code point hhh..
\uhhhh character with hex code hhhh (when PCRE2_ALT_BSUX is set)
</pre>
+There are some legacy applications where the escape sequence \r is expected to
+match a newline. If the PCRE2_EXTRA_ESCAPED_CR_IS_LF option is set, \r in a
+pattern is converted to \n so that it matches a LF (linefeed) instead of a CR
+(carriage return) character.
+</P>
+<P>
The \N{U+hhh..} escape sequence is recognized only when the PCRE2_UTF option
is set, that is, when PCRE2 is operating in a Unicode mode. Perl also uses
\N{name} to specify characters by Unicode name; PCRE2 does not support this.
@@ -3624,7 +3630,7 @@
</P>
<br><a name="SEC30" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 04 September 2018
+Last updated: 21 September 2018
<br>
Copyright © 1997-2018 University of Cambridge.
<br>
Modified: code/trunk/doc/html/pcre2test.html
===================================================================
--- code/trunk/doc/html/pcre2test.html 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/html/pcre2test.html 2018-09-21 16:59:48 UTC (rev 1017)
@@ -606,6 +606,7 @@
/s dotall set PCRE2_DOTALL
dupnames set PCRE2_DUPNAMES
endanchored set PCRE2_ENDANCHORED
+ escaped_cr_is_lf set PCRE2_EXTRA_ESCAPED_CR_IS_LF
/x extended set PCRE2_EXTENDED
/xx extended_more set PCRE2_EXTENDED_MORE
firstline set PCRE2_FIRSTLINE
@@ -2039,7 +2040,7 @@
</P>
<br><a name="SEC21" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 17 September 2018
+Last updated: 21 September 2018
<br>
Copyright © 1997-2018 University of Cambridge.
<br>
Modified: code/trunk/doc/pcre2.txt
===================================================================
--- code/trunk/doc/pcre2.txt 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2.txt 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1849,22 +1849,31 @@
option means that typos in patterns may go undetected and have unex-
pected results. This is a dangerous option. Use with care.
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF
+
+ There are some legacy applications where the escape sequence \r in a
+ pattern is expected to match a newline. If this option is set, \r in a
+ pattern is converted to \n so that it matches a LF (linefeed) instead
+ of a CR (carriage return) character. The option does not affect a lit-
+ eral CR in the pattern, nor does it affect CR specified as an explicit
+ code point such as \x{0D}.
+
PCRE2_EXTRA_MATCH_LINE
- This option is provided for use by the -x option of pcre2grep. It
- causes the pattern only to match complete lines. This is achieved by
- automatically inserting the code for "^(?:" at the start of the com-
- piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set,
- the matched line may be in the middle of the subject string. This
+ This option is provided for use by the -x option of pcre2grep. It
+ causes the pattern only to match complete lines. This is achieved by
+ automatically inserting the code for "^(?:" at the start of the com-
+ piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set,
+ the matched line may be in the middle of the subject string. This
option can be used with PCRE2_LITERAL.
PCRE2_EXTRA_MATCH_WORD
- This option is provided for use by the -w option of pcre2grep. It
- causes the pattern only to match strings that have a word boundary at
- the start and the end. This is achieved by automatically inserting the
- code for "\b(?:" at the start of the compiled pattern and ")\b" at the
- end. The option may be used with PCRE2_LITERAL. However, it is ignored
+ This option is provided for use by the -w option of pcre2grep. It
+ causes the pattern only to match strings that have a word boundary at
+ the start and the end. This is achieved by automatically inserting the
+ code for "\b(?:" at the start of the compiled pattern and ")\b" at the
+ end. The option may be used with PCRE2_LITERAL. However, it is ignored
if PCRE2_EXTRA_MATCH_LINE is also set.
@@ -1887,53 +1896,53 @@
void pcre2_jit_stack_free(pcre2_jit_stack *jit_stack);
- These functions provide support for JIT compilation, which, if the
- just-in-time compiler is available, further processes a compiled pat-
+ These functions provide support for JIT compilation, which, if the
+ just-in-time compiler is available, further processes a compiled pat-
tern into machine code that executes much faster than the pcre2_match()
- interpretive matching function. Full details are given in the pcre2jit
+ interpretive matching function. Full details are given in the pcre2jit
documentation.
- JIT compilation is a heavyweight optimization. It can take some time
- for patterns to be analyzed, and for one-off matches and simple pat-
- terns the benefit of faster execution might be offset by a much slower
- compilation time. Most (but not all) patterns can be optimized by the
+ JIT compilation is a heavyweight optimization. It can take some time
+ for patterns to be analyzed, and for one-off matches and simple pat-
+ terns the benefit of faster execution might be offset by a much slower
+ compilation time. Most (but not all) patterns can be optimized by the
JIT compiler.
LOCALE SUPPORT
- PCRE2 handles caseless matching, and determines whether characters are
- letters, digits, or whatever, by reference to a set of tables, indexed
- by character code point. This applies only to characters whose code
- points are less than 256. By default, higher-valued code points never
- match escapes such as \w or \d. However, if PCRE2 is built with Uni-
+ PCRE2 handles caseless matching, and determines whether characters are
+ letters, digits, or whatever, by reference to a set of tables, indexed
+ by character code point. This applies only to characters whose code
+ points are less than 256. By default, higher-valued code points never
+ match escapes such as \w or \d. However, if PCRE2 is built with Uni-
code support, all characters can be tested with \p and \P, or, alterna-
- tively, the PCRE2_UCP option can be set when a pattern is compiled;
- this causes \w and friends to use Unicode property support instead of
+ tively, the PCRE2_UCP option can be set when a pattern is compiled;
+ this causes \w and friends to use Unicode property support instead of
the built-in tables.
- The use of locales with Unicode is discouraged. If you are handling
- characters with code points greater than 128, you should either use
+ The use of locales with Unicode is discouraged. If you are handling
+ characters with code points greater than 128, you should either use
Unicode support, or use locales, but not try to mix the two.
- PCRE2 contains an internal set of character tables that are used by
- default. These are sufficient for many applications. Normally, the
+ PCRE2 contains an internal set of character tables that are used by
+ default. These are sufficient for many applications. Normally, the
internal tables recognize only ASCII characters. However, when PCRE2 is
built, it is possible to cause the internal tables to be rebuilt in the
default "C" locale of the local system, which may cause them to be dif-
ferent.
- The internal tables can be overridden by tables supplied by the appli-
- cation that calls PCRE2. These may be created in a different locale
- from the default. As more and more applications change to using Uni-
+ The internal tables can be overridden by tables supplied by the appli-
+ cation that calls PCRE2. These may be created in a different locale
+ from the default. As more and more applications change to using Uni-
code, the need for this locale support is expected to die away.
- External tables are built by calling the pcre2_maketables() function,
- in the relevant locale. The result can be passed to pcre2_compile() as
- often as necessary, by creating a compile context and calling
- pcre2_set_character_tables() to set the tables pointer therein. For
- example, to build and use tables that are appropriate for the French
- locale (where accented characters with values greater than 128 are
+ External tables are built by calling the pcre2_maketables() function,
+ in the relevant locale. The result can be passed to pcre2_compile() as
+ often as necessary, by creating a compile context and calling
+ pcre2_set_character_tables() to set the tables pointer therein. For
+ example, to build and use tables that are appropriate for the French
+ locale (where accented characters with values greater than 128 are
treated as letters), the following code could be used:
setlocale(LC_CTYPE, "fr_FR");
@@ -1942,15 +1951,15 @@
pcre2_set_character_tables(ccontext, tables);
re = pcre2_compile(..., ccontext);
- The locale name "fr_FR" is used on Linux and other Unix-like systems;
- if you are using Windows, the name for the French locale is "french".
- It is the caller's responsibility to ensure that the memory containing
+ The locale name "fr_FR" is used on Linux and other Unix-like systems;
+ if you are using Windows, the name for the French locale is "french".
+ It is the caller's responsibility to ensure that the memory containing
the tables remains available for as long as it is needed.
The pointer that is passed (via the compile context) to pcre2_compile()
- is saved with the compiled pattern, and the same tables are used by
- pcre2_match() and pcre_dfa_match(). Thus, for any single pattern, com-
- pilation and matching both happen in the same locale, but different
+ is saved with the compiled pattern, and the same tables are used by
+ pcre2_match() and pcre_dfa_match(). Thus, for any single pattern, com-
+ pilation and matching both happen in the same locale, but different
patterns can be processed in different locales.
@@ -1958,13 +1967,13 @@
int pcre2_pattern_info(const pcre2 *code, uint32_t what, void *where);
- The pcre2_pattern_info() function returns general information about a
+ The pcre2_pattern_info() function returns general information about a
compiled pattern. For information about callouts, see the next section.
- The first argument for pcre2_pattern_info() is a pointer to the com-
+ The first argument for pcre2_pattern_info() is a pointer to the com-
piled pattern. The second argument specifies which piece of information
- is required, and the third argument is a pointer to a variable to
- receive the data. If the third argument is NULL, the first argument is
- ignored, and the function returns the size in bytes of the variable
+ is required, and the third argument is a pointer to a variable to
+ receive the data. If the third argument is NULL, the first argument is
+ ignored, and the function returns the size in bytes of the variable
that is required for the information requested. Otherwise, the yield of
the function is zero for success, or one of the following negative num-
bers:
@@ -1974,9 +1983,9 @@
PCRE2_ERROR_BADOPTION the value of what was invalid
PCRE2_ERROR_UNSET the requested field is not set
- The "magic number" is placed at the start of each compiled pattern as
- an simple check against passing an arbitrary memory pointer. Here is a
- typical call of pcre2_pattern_info(), to obtain the length of the com-
+ The "magic number" is placed at the start of each compiled pattern as
+ an simple check against passing an arbitrary memory pointer. Here is a
+ typical call of pcre2_pattern_info(), to obtain the length of the com-
piled pattern:
int rc;
@@ -1994,22 +2003,22 @@
PCRE2_INFO_EXTRAOPTIONS
Return copies of the pattern's options. The third argument should point
- to a uint32_t variable. PCRE2_INFO_ARGOPTIONS returns exactly the
- options that were passed to pcre2_compile(), whereas PCRE2_INFO_ALLOP-
- TIONS returns the compile options as modified by any top-level (*XXX)
- option settings such as (*UTF) at the start of the pattern itself.
- PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the
- compile context by calling the pcre2_set_compile_extra_options() func-
+ to a uint32_t variable. PCRE2_INFO_ARGOPTIONS returns exactly the
+ options that were passed to pcre2_compile(), whereas PCRE2_INFO_ALLOP-
+ TIONS returns the compile options as modified by any top-level (*XXX)
+ option settings such as (*UTF) at the start of the pattern itself.
+ PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the
+ compile context by calling the pcre2_set_compile_extra_options() func-
tion.
- For example, if the pattern /(*UTF)abc/ is compiled with the
- PCRE2_EXTENDED option, the result for PCRE2_INFO_ALLOPTIONS is
- PCRE2_EXTENDED and PCRE2_UTF. Option settings such as (?i) that can
- change within a pattern do not affect the result of PCRE2_INFO_ALLOP-
+ For example, if the pattern /(*UTF)abc/ is compiled with the
+ PCRE2_EXTENDED option, the result for PCRE2_INFO_ALLOPTIONS is
+ PCRE2_EXTENDED and PCRE2_UTF. Option settings such as (?i) that can
+ change within a pattern do not affect the result of PCRE2_INFO_ALLOP-
TIONS, even if they appear right at the start of the pattern. (This was
different in some earlier releases.)
- A pattern compiled without PCRE2_ANCHORED is automatically anchored by
+ A pattern compiled without PCRE2_ANCHORED is automatically anchored by
PCRE2 if the first significant item in every top-level branch is one of
the following:
@@ -2018,7 +2027,7 @@
\G always
.* sometimes - see below
- When .* is the first significant item, anchoring is possible only when
+ When .* is the first significant item, anchoring is possible only when
all the following are true:
.* is not in an atomic group
@@ -2028,71 +2037,71 @@
Neither (*PRUNE) nor (*SKIP) appears in the pattern
PCRE2_NO_DOTSTAR_ANCHOR is not set
- For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in
+ For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in
the options returned for PCRE2_INFO_ALLOPTIONS.
PCRE2_INFO_BACKREFMAX
- Return the number of the highest backreference in the pattern. The
- third argument should point to an uint32_t variable. Named subpatterns
- acquire numbers as well as names, and these count towards the highest
- backreference. Backreferences such as \4 or \g{12} match the captured
- characters of the given group, but in addition, the check that a cap-
- turing group is set in a conditional subpattern such as (?(3)a|b) is
+ Return the number of the highest backreference in the pattern. The
+ third argument should point to an uint32_t variable. Named subpatterns
+ acquire numbers as well as names, and these count towards the highest
+ backreference. Backreferences such as \4 or \g{12} match the captured
+ characters of the given group, but in addition, the check that a cap-
+ turing group is set in a conditional subpattern such as (?(3)a|b) is
also a backreference. Zero is returned if there are no backreferences.
PCRE2_INFO_BSR
- The output is a uint32_t integer whose value indicates what character
- sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE
- means that \R matches any Unicode line ending sequence; a value of
+ The output is a uint32_t integer whose value indicates what character
+ sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE
+ means that \R matches any Unicode line ending sequence; a value of
PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF.
PCRE2_INFO_CAPTURECOUNT
- Return the highest capturing subpattern number in the pattern. In pat-
+ Return the highest capturing subpattern number in the pattern. In pat-
terns where (?| is not used, this is also the total number of capturing
subpatterns. The third argument should point to an uint32_t variable.
PCRE2_INFO_DEPTHLIMIT
- If the pattern set a backtracking depth limit by including an item of
- the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The
+ If the pattern set a backtracking depth limit by including an item of
+ the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The
third argument should point to a uint32_t integer. If no such value has
- been set, the call to pcre2_pattern_info() returns the error
+ been set, the call to pcre2_pattern_info() returns the error
PCRE2_ERROR_UNSET. Note that this limit will only be used during match-
- ing if it is less than the limit set or defaulted by the caller of the
+ ing if it is less than the limit set or defaulted by the caller of the
match function.
PCRE2_INFO_FIRSTBITMAP
- In the absence of a single first code unit for a non-anchored pattern,
- pcre2_compile() may construct a 256-bit table that defines a fixed set
- of values for the first code unit in any match. For example, a pattern
- that starts with [abc] results in a table with three bits set. When
- code unit values greater than 255 are supported, the flag bit for 255
- means "any code unit of value 255 or above". If such a table was con-
- structed, a pointer to it is returned. Otherwise NULL is returned. The
+ In the absence of a single first code unit for a non-anchored pattern,
+ pcre2_compile() may construct a 256-bit table that defines a fixed set
+ of values for the first code unit in any match. For example, a pattern
+ that starts with [abc] results in a table with three bits set. When
+ code unit values greater than 255 are supported, the flag bit for 255
+ means "any code unit of value 255 or above". If such a table was con-
+ structed, a pointer to it is returned. Otherwise NULL is returned. The
third argument should point to a const uint8_t * variable.
PCRE2_INFO_FIRSTCODETYPE
Return information about the first code unit of any matched string, for
- a non-anchored pattern. The third argument should point to an uint32_t
- variable. If there is a fixed first value, for example, the letter "c"
- from a pattern such as (cat|cow|coyote), 1 is returned, and the value
- can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed
- first value, but it is known that a match can occur only at the start
- of the subject or following a newline in the subject, 2 is returned.
+ a non-anchored pattern. The third argument should point to an uint32_t
+ variable. If there is a fixed first value, for example, the letter "c"
+ from a pattern such as (cat|cow|coyote), 1 is returned, and the value
+ can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed
+ first value, but it is known that a match can occur only at the start
+ of the subject or following a newline in the subject, 2 is returned.
Otherwise, and for anchored patterns, 0 is returned.
PCRE2_INFO_FIRSTCODEUNIT
- Return the value of the first code unit of any matched string for a
- pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0.
- The third argument should point to an uint32_t variable. In the 8-bit
- library, the value is always less than 256. In the 16-bit library the
- value can be up to 0xffff. In the 32-bit library in UTF-32 mode the
+ Return the value of the first code unit of any matched string for a
+ pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0.
+ The third argument should point to an uint32_t variable. In the 8-bit
+ library, the value is always less than 256. In the 16-bit library the
+ value can be up to 0xffff. In the 32-bit library in UTF-32 mode the
value can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32
mode.
@@ -2099,23 +2108,23 @@
PCRE2_INFO_FRAMESIZE
Return the size (in bytes) of the data frames that are used to remember
- backtracking positions when the pattern is processed by pcre2_match()
- without the use of JIT. The third argument should point to a size_t
+ backtracking positions when the pattern is processed by pcre2_match()
+ without the use of JIT. The third argument should point to a size_t
variable. The frame size depends on the number of capturing parentheses
- in the pattern. Each additional capturing group adds two PCRE2_SIZE
+ in the pattern. Each additional capturing group adds two PCRE2_SIZE
variables.
PCRE2_INFO_HASBACKSLASHC
- Return 1 if the pattern contains any instances of \C, otherwise 0. The
+ Return 1 if the pattern contains any instances of \C, otherwise 0. The
third argument should point to an uint32_t variable.
PCRE2_INFO_HASCRORLF
- Return 1 if the pattern contains any explicit matches for CR or LF
+ Return 1 if the pattern contains any explicit matches for CR or LF
characters, otherwise 0. The third argument should point to an uint32_t
- variable. An explicit match is either a literal CR or LF character, or
- \r or \n or one of the equivalent hexadecimal or octal escape
+ variable. An explicit match is either a literal CR or LF character, or
+ \r or \n or one of the equivalent hexadecimal or octal escape
sequences.
PCRE2_INFO_HEAPLIMIT
@@ -2123,81 +2132,81 @@
If the pattern set a heap memory limit by including an item of the form
(*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argu-
ment should point to a uint32_t integer. If no such value has been set,
- the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UNSET.
- Note that this limit will only be used during matching if it is less
+ the call to pcre2_pattern_info() returns the error PCRE2_ERROR_UNSET.
+ Note that this limit will only be used during matching if it is less
than the limit set or defaulted by the caller of the match function.
PCRE2_INFO_JCHANGED
- Return 1 if the (?J) or (?-J) option setting is used in the pattern,
- otherwise 0. The third argument should point to an uint32_t variable.
- (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec-
+ Return 1 if the (?J) or (?-J) option setting is used in the pattern,
+ otherwise 0. The third argument should point to an uint32_t variable.
+ (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec-
tively.
PCRE2_INFO_JITSIZE
- If the compiled pattern was successfully processed by pcre2_jit_com-
- pile(), return the size of the JIT compiled code, otherwise return
+ If the compiled pattern was successfully processed by pcre2_jit_com-
+ pile(), return the size of the JIT compiled code, otherwise return
zero. The third argument should point to a size_t variable.
PCRE2_INFO_LASTCODETYPE
- Returns 1 if there is a rightmost literal code unit that must exist in
- any matched string, other than at its start. The third argument should
- point to an uint32_t variable. If there is no such value, 0 is
- returned. When 1 is returned, the code unit value itself can be
- retrieved using PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last
- literal value is recorded only if it follows something of variable
- length. For example, for the pattern /^a\d+z\d+/ the returned value is
- 1 (with "z" returned from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/
+ Returns 1 if there is a rightmost literal code unit that must exist in
+ any matched string, other than at its start. The third argument should
+ point to an uint32_t variable. If there is no such value, 0 is
+ returned. When 1 is returned, the code unit value itself can be
+ retrieved using PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last
+ literal value is recorded only if it follows something of variable
+ length. For example, for the pattern /^a\d+z\d+/ the returned value is
+ 1 (with "z" returned from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/
the returned value is 0.
PCRE2_INFO_LASTCODEUNIT
- Return the value of the rightmost literal code unit that must exist in
- any matched string, other than at its start, for a pattern where
+ Return the value of the rightmost literal code unit that must exist in
+ any matched string, other than at its start, for a pattern where
PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argu-
ment should point to an uint32_t variable.
PCRE2_INFO_MATCHEMPTY
- Return 1 if the pattern might match an empty string, otherwise 0. The
- third argument should point to an uint32_t variable. When a pattern
+ Return 1 if the pattern might match an empty string, otherwise 0. The
+ third argument should point to an uint32_t variable. When a pattern
contains recursive subroutine calls it is not always possible to deter-
- mine whether or not it can match an empty string. PCRE2 takes a cau-
+ mine whether or not it can match an empty string. PCRE2 takes a cau-
tious approach and returns 1 in such cases.
PCRE2_INFO_MATCHLIMIT
- If the pattern set a match limit by including an item of the form
- (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third
- argument should point to a uint32_t integer. If no such value has been
- set, the call to pcre2_pattern_info() returns the error
+ If the pattern set a match limit by including an item of the form
+ (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third
+ argument should point to a uint32_t integer. If no such value has been
+ set, the call to pcre2_pattern_info() returns the error
PCRE2_ERROR_UNSET. Note that this limit will only be used during match-
- ing if it is less than the limit set or defaulted by the caller of the
+ ing if it is less than the limit set or defaulted by the caller of the
match function.
PCRE2_INFO_MAXLOOKBEHIND
Return the number of characters (not code units) in the longest lookbe-
- hind assertion in the pattern. The third argument should point to a
- uint32_t integer. This information is useful when doing multi-segment
- matching using the partial matching facilities. Note that the simple
+ hind assertion in the pattern. The third argument should point to a
+ uint32_t integer. This information is useful when doing multi-segment
+ matching using the partial matching facilities. Note that the simple
assertions \b and \B require a one-character lookbehind. \A also regis-
- ters a one-character lookbehind, though it does not actually inspect
- the previous character. This is to ensure that at least one character
- from the old segment is retained when a new segment is processed. Oth-
- erwise, if there are no lookbehinds in the pattern, \A might match
+ ters a one-character lookbehind, though it does not actually inspect
+ the previous character. This is to ensure that at least one character
+ from the old segment is retained when a new segment is processed. Oth-
+ erwise, if there are no lookbehinds in the pattern, \A might match
incorrectly at the start of a second or subsequent segment.
PCRE2_INFO_MINLENGTH
- If a minimum length for matching subject strings was computed, its
- value is returned. Otherwise the returned value is 0. The value is a
- number of characters, which in UTF mode may be different from the num-
- ber of code units. The third argument should point to an uint32_t
- variable. The value is a lower bound to the length of any matching
- string. There may not be any strings of that length that do actually
+ If a minimum length for matching subject strings was computed, its
+ value is returned. Otherwise the returned value is 0. The value is a
+ number of characters, which in UTF mode may be different from the num-
+ ber of code units. The third argument should point to an uint32_t
+ variable. The value is a lower bound to the length of any matching
+ string. There may not be any strings of that length that do actually
match, but every string that does match is at least that long.
PCRE2_INFO_NAMECOUNT
@@ -2205,50 +2214,50 @@
PCRE2_INFO_NAMETABLE
PCRE2 supports the use of named as well as numbered capturing parenthe-
- ses. The names are just an additional way of identifying the parenthe-
+ ses. The names are just an additional way of identifying the parenthe-
ses, which still acquire numbers. Several convenience functions such as
- pcre2_substring_get_byname() are provided for extracting captured sub-
- strings by name. It is also possible to extract the data directly, by
- first converting the name to a number in order to access the correct
- pointers in the output vector (described with pcre2_match() below). To
- do the conversion, you need to use the name-to-number map, which is
+ pcre2_substring_get_byname() are provided for extracting captured sub-
+ strings by name. It is also possible to extract the data directly, by
+ first converting the name to a number in order to access the correct
+ pointers in the output vector (described with pcre2_match() below). To
+ do the conversion, you need to use the name-to-number map, which is
described by these three values.
- The map consists of a number of fixed-size entries. PCRE2_INFO_NAME-
- COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives
- the size of each entry in code units; both of these return a uint32_t
+ The map consists of a number of fixed-size entries. PCRE2_INFO_NAME-
+ COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives
+ the size of each entry in code units; both of these return a uint32_t
value. The entry size depends on the length of the longest name.
PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table.
- This is a PCRE2_SPTR pointer to a block of code units. In the 8-bit
- library, the first two bytes of each entry are the number of the cap-
+ This is a PCRE2_SPTR pointer to a block of code units. In the 8-bit
+ library, the first two bytes of each entry are the number of the cap-
turing parenthesis, most significant byte first. In the 16-bit library,
- the pointer points to 16-bit code units, the first of which contains
- the parenthesis number. In the 32-bit library, the pointer points to
- 32-bit code units, the first of which contains the parenthesis number.
+ the pointer points to 16-bit code units, the first of which contains
+ the parenthesis number. In the 32-bit library, the pointer points to
+ 32-bit code units, the first of which contains the parenthesis number.
The rest of the entry is the corresponding name, zero terminated.
- The names are in alphabetical order. If (?| is used to create multiple
- groups with the same number, as described in the section on duplicate
- subpattern numbers in the pcre2pattern page, the groups may be given
- the same name, but there is only one entry in the table. Different
+ The names are in alphabetical order. If (?| is used to create multiple
+ groups with the same number, as described in the section on duplicate
+ subpattern numbers in the pcre2pattern page, the groups may be given
+ the same name, but there is only one entry in the table. Different
names for groups of the same number are not permitted.
- Duplicate names for subpatterns with different numbers are permitted,
- but only if PCRE2_DUPNAMES is set. They appear in the table in the
- order in which they were found in the pattern. In the absence of (?|
- this is the order of increasing number; when (?| is used this is not
+ Duplicate names for subpatterns with different numbers are permitted,
+ but only if PCRE2_DUPNAMES is set. They appear in the table in the
+ order in which they were found in the pattern. In the absence of (?|
+ this is the order of increasing number; when (?| is used this is not
necessarily the case because later subpatterns may have lower numbers.
- As a simple example of the name/number table, consider the following
- pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED
+ As a simple example of the name/number table, consider the following
+ pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED
is set, so white space - including newlines - is ignored):
(?<date> (?<year>(\d\d)?\d\d) -
(?<month>\d\d) - (?<day>\d\d) )
- There are four named subpatterns, so the table has four entries, and
- each entry in the table is eight bytes long. The table is as follows,
+ There are four named subpatterns, so the table has four entries, and
+ each entry in the table is eight bytes long. The table is as follows,
with non-printing bytes shows in hexadecimal, and undefined bytes shown
as ??:
@@ -2257,8 +2266,8 @@
00 04 m o n t h 00
00 02 y e a r 00 ??
- When writing code to extract data from named subpatterns using the
- name-to-number map, remember that the length of the entries is likely
+ When writing code to extract data from named subpatterns using the
+ name-to-number map, remember that the length of the entries is likely
to be different for each compiled pattern.
PCRE2_INFO_NEWLINE
@@ -2277,14 +2286,14 @@
PCRE2_INFO_SIZE
- Return the size of the compiled pattern in bytes (for all three
- libraries). The third argument should point to a size_t variable. This
- value includes the size of the general data block that precedes the
- code units of the compiled pattern itself. The value that is used when
- pcre2_compile() is getting memory in which to place the compiled pat-
- tern may be slightly larger than the value returned by this option,
- because there are cases where the code that calculates the size has to
- over-estimate. Processing a pattern with the JIT compiler does not
+ Return the size of the compiled pattern in bytes (for all three
+ libraries). The third argument should point to a size_t variable. This
+ value includes the size of the general data block that precedes the
+ code units of the compiled pattern itself. The value that is used when
+ pcre2_compile() is getting memory in which to place the compiled pat-
+ tern may be slightly larger than the value returned by this option,
+ because there are cases where the code that calculates the size has to
+ over-estimate. Processing a pattern with the JIT compiler does not
alter the value returned by this option.
@@ -2295,30 +2304,30 @@
void *user_data);
A script language that supports the use of string arguments in callouts
- might like to scan all the callouts in a pattern before running the
+ might like to scan all the callouts in a pattern before running the
match. This can be done by calling pcre2_callout_enumerate(). The first
- argument is a pointer to a compiled pattern, the second points to a
- callback function, and the third is arbitrary user data. The callback
- function is called for every callout in the pattern in the order in
+ argument is a pointer to a compiled pattern, the second points to a
+ callback function, and the third is arbitrary user data. The callback
+ function is called for every callout in the pattern in the order in
which they appear. Its first argument is a pointer to a callout enumer-
- ation block, and its second argument is the user_data value that was
- passed to pcre2_callout_enumerate(). The contents of the callout enu-
- meration block are described in the pcre2callout documentation, which
+ ation block, and its second argument is the user_data value that was
+ passed to pcre2_callout_enumerate(). The contents of the callout enu-
+ meration block are described in the pcre2callout documentation, which
also gives further details about callouts.
SERIALIZATION AND PRECOMPILING
- It is possible to save compiled patterns on disc or elsewhere, and
- reload them later, subject to a number of restrictions. The host on
- which the patterns are reloaded must be running the same version of
+ It is possible to save compiled patterns on disc or elsewhere, and
+ reload them later, subject to a number of restrictions. The host on
+ which the patterns are reloaded must be running the same version of
PCRE2, with the same code unit width, and must also have the same endi-
- anness, pointer width, and PCRE2_SIZE type. Before compiled patterns
- can be saved, they must be converted to a "serialized" form, which in
- the case of PCRE2 is really just a bytecode dump. The functions whose
- names begin with pcre2_serialize_ are used for converting to and from
- the serialized form. They are described in the pcre2serialize documen-
- tation. Note that PCRE2 serialization does not convert compiled pat-
+ anness, pointer width, and PCRE2_SIZE type. Before compiled patterns
+ can be saved, they must be converted to a "serialized" form, which in
+ the case of PCRE2 is really just a bytecode dump. The functions whose
+ names begin with pcre2_serialize_ are used for converting to and from
+ the serialized form. They are described in the pcre2serialize documen-
+ tation. Note that PCRE2 serialization does not convert compiled pat-
terns to an abstract format like Java or .NET serialization.
@@ -2332,57 +2341,57 @@
void pcre2_match_data_free(pcre2_match_data *match_data);
- Information about a successful or unsuccessful match is placed in a
- match data block, which is an opaque structure that is accessed by
- function calls. In particular, the match data block contains a vector
- of offsets into the subject string that define the matched part of the
- subject and any substrings that were captured. This is known as the
+ Information about a successful or unsuccessful match is placed in a
+ match data block, which is an opaque structure that is accessed by
+ function calls. In particular, the match data block contains a vector
+ of offsets into the subject string that define the matched part of the
+ subject and any substrings that were captured. This is known as the
ovector.
- Before calling pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match()
+ Before calling pcre2_match(), pcre2_dfa_match(), or pcre2_jit_match()
you must create a match data block by calling one of the creation func-
- tions above. For pcre2_match_data_create(), the first argument is the
- number of pairs of offsets in the ovector. One pair of offsets is
+ tions above. For pcre2_match_data_create(), the first argument is the
+ number of pairs of offsets in the ovector. One pair of offsets is
required to identify the string that matched the whole pattern, with an
- additional pair for each captured substring. For example, a value of 4
- creates enough space to record the matched portion of the subject plus
- three captured substrings. A minimum of at least 1 pair is imposed by
+ additional pair for each captured substring. For example, a value of 4
+ creates enough space to record the matched portion of the subject plus
+ three captured substrings. A minimum of at least 1 pair is imposed by
pcre2_match_data_create(), so it is always possible to return the over-
all matched string.
The second argument of pcre2_match_data_create() is a pointer to a gen-
- eral context, which can specify custom memory management for obtaining
+ eral context, which can specify custom memory management for obtaining
the memory for the match data block. If you are not using custom memory
management, pass NULL, which causes malloc() to be used.
- For pcre2_match_data_create_from_pattern(), the first argument is a
+ For pcre2_match_data_create_from_pattern(), the first argument is a
pointer to a compiled pattern. The ovector is created to be exactly the
right size to hold all the substrings a pattern might capture. The sec-
- ond argument is again a pointer to a general context, but in this case
+ ond argument is again a pointer to a general context, but in this case
if NULL is passed, the memory is obtained using the same allocator that
was used for the compiled pattern (custom or default).
- A match data block can be used many times, with the same or different
- compiled patterns. You can extract information from a match data block
+ A match data block can be used many times, with the same or different
+ compiled patterns. You can extract information from a match data block
after a match operation has finished, using functions that are
- described in the sections on matched strings and other match data
+ described in the sections on matched strings and other match data
below.
- When a call of pcre2_match() fails, valid data is available in the
- match block only when the error is PCRE2_ERROR_NOMATCH,
- PCRE2_ERROR_PARTIAL, or one of the error codes for an invalid UTF
+ When a call of pcre2_match() fails, valid data is available in the
+ match block only when the error is PCRE2_ERROR_NOMATCH,
+ PCRE2_ERROR_PARTIAL, or one of the error codes for an invalid UTF
string. Exactly what is available depends on the error, and is detailed
below.
- When one of the matching functions is called, pointers to the compiled
- pattern and the subject string are set in the match data block so that
- they can be referenced by the extraction functions. After running a
- match, you must not free a compiled pattern or a subject string until
- after all operations on the match data block (for that match) have
+ When one of the matching functions is called, pointers to the compiled
+ pattern and the subject string are set in the match data block so that
+ they can be referenced by the extraction functions. After running a
+ match, you must not free a compiled pattern or a subject string until
+ after all operations on the match data block (for that match) have
taken place.
- When a match data block itself is no longer needed, it should be freed
- by calling pcre2_match_data_free(). If this function is called with a
+ When a match data block itself is no longer needed, it should be freed
+ by calling pcre2_match_data_free(). If this function is called with a
NULL argument, it returns immediately, without doing anything.
@@ -2393,15 +2402,15 @@
uint32_t options, pcre2_match_data *match_data,
pcre2_match_context *mcontext);
- The function pcre2_match() is called to match a subject string against
- a compiled pattern, which is passed in the code argument. You can call
+ The function pcre2_match() is called to match a subject string against
+ a compiled pattern, which is passed in the code argument. You can call
pcre2_match() with the same code argument as many times as you like, in
- order to find multiple matches in the subject string or to match dif-
+ order to find multiple matches in the subject string or to match dif-
ferent subject strings with the same pattern.
- This function is the main matching facility of the library, and it
- operates in a Perl-like manner. For specialist use there is also an
- alternative matching function, which is described below in the section
+ This function is the main matching facility of the library, and it
+ operates in a Perl-like manner. For specialist use there is also an
+ alternative matching function, which is described below in the section
about the pcre2_dfa_match() function.
Here is an example of a simple call to pcre2_match():
@@ -2416,7 +2425,7 @@
md, /* the match data block */
NULL); /* a match context; NULL means use defaults */
- If the subject string is zero-terminated, the length can be given as
+ If the subject string is zero-terminated, the length can be given as
PCRE2_ZERO_TERMINATED. A match context must be provided if certain less
common matching parameters are to be changed. For details, see the sec-
tion on the match context above.
@@ -2423,92 +2432,92 @@
The string to be matched by pcre2_match()
- The subject string is passed to pcre2_match() as a pointer in subject,
- a length in length, and a starting offset in startoffset. The length
- and offset are in code units, not characters. That is, they are in
- bytes for the 8-bit library, 16-bit code units for the 16-bit library,
- and 32-bit code units for the 32-bit library, whether or not UTF pro-
+ The subject string is passed to pcre2_match() as a pointer in subject,
+ a length in length, and a starting offset in startoffset. The length
+ and offset are in code units, not characters. That is, they are in
+ bytes for the 8-bit library, 16-bit code units for the 16-bit library,
+ and 32-bit code units for the 32-bit library, whether or not UTF pro-
cessing is enabled.
If startoffset is greater than the length of the subject, pcre2_match()
- returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the
- search for a match starts at the beginning of the subject, and this is
+ returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the
+ search for a match starts at the beginning of the subject, and this is
by far the most common case. In UTF-8 or UTF-16 mode, the starting off-
- set must point to the start of a character, or to the end of the sub-
- ject (in UTF-32 mode, one code unit equals one character, so all off-
- sets are valid). Like the pattern string, the subject may contain
+ set must point to the start of a character, or to the end of the sub-
+ ject (in UTF-32 mode, one code unit equals one character, so all off-
+ sets are valid). Like the pattern string, the subject may contain
binary zeros.
- A non-zero starting offset is useful when searching for another match
- in the same subject by calling pcre2_match() again after a previous
- success. Setting startoffset differs from passing over a shortened
- string and setting PCRE2_NOTBOL in the case of a pattern that begins
+ A non-zero starting offset is useful when searching for another match
+ in the same subject by calling pcre2_match() again after a previous
+ success. Setting startoffset differs from passing over a shortened
+ string and setting PCRE2_NOTBOL in the case of a pattern that begins
with any kind of lookbehind. For example, consider the pattern
\Biss\B
- which finds occurrences of "iss" in the middle of words. (\B matches
- only if the current position in the subject is not a word boundary.)
+ which finds occurrences of "iss" in the middle of words. (\B matches
+ only if the current position in the subject is not a word boundary.)
When applied to the string "Mississipi" the first call to pcre2_match()
- finds the first occurrence. If pcre2_match() is called again with just
- the remainder of the subject, namely "issipi", it does not match,
+ finds the first occurrence. If pcre2_match() is called again with just
+ the remainder of the subject, namely "issipi", it does not match,
because \B is always false at the start of the subject, which is deemed
- to be a word boundary. However, if pcre2_match() is passed the entire
+ to be a word boundary. However, if pcre2_match() is passed the entire
string again, but with startoffset set to 4, it finds the second occur-
- rence of "iss" because it is able to look behind the starting point to
+ rence of "iss" because it is able to look behind the starting point to
discover that it is preceded by a letter.
- Finding all the matches in a subject is tricky when the pattern can
+ Finding all the matches in a subject is tricky when the pattern can
match an empty string. It is possible to emulate Perl's /g behaviour by
- first trying the match again at the same offset, with the
- PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that
- fails, advancing the starting offset and trying an ordinary match
- again. There is some code that demonstrates how to do this in the
- pcre2demo sample program. In the most general case, you have to check
- to see if the newline convention recognizes CRLF as a newline, and if
- so, and the current character is CR followed by LF, advance the start-
+ first trying the match again at the same offset, with the
+ PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that
+ fails, advancing the starting offset and trying an ordinary match
+ again. There is some code that demonstrates how to do this in the
+ pcre2demo sample program. In the most general case, you have to check
+ to see if the newline convention recognizes CRLF as a newline, and if
+ so, and the current character is CR followed by LF, advance the start-
ing offset by two characters instead of one.
If a non-zero starting offset is passed when the pattern is anchored, a
single attempt to match at the given offset is made. This can only suc-
- ceed if the pattern does not require the match to be at the start of
- the subject. In other words, the anchoring must be the result of set-
- ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not
+ ceed if the pattern does not require the match to be at the start of
+ the subject. In other words, the anchoring must be the result of set-
+ ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not
by starting the pattern with ^ or \A.
Option bits for pcre2_match()
The unused bits of the options argument for pcre2_match() must be zero.
- The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDANCHORED,
- PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART,
- PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PAR-
+ The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDANCHORED,
+ PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART,
+ PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PAR-
TIAL_SOFT. Their action is described below.
- Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup-
- ported by the just-in-time (JIT) compiler. If it is set, JIT matching
- is disabled and the interpretive code in pcre2_match() is run. Apart
- from PCRE2_NO_JIT (obviously), the remaining options are supported for
+ Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup-
+ ported by the just-in-time (JIT) compiler. If it is set, JIT matching
+ is disabled and the interpretive code in pcre2_match() is run. Apart
+ from PCRE2_NO_JIT (obviously), the remaining options are supported for
JIT matching.
PCRE2_ANCHORED
The PCRE2_ANCHORED option limits pcre2_match() to matching at the first
- matching position. If a pattern was compiled with PCRE2_ANCHORED, or
- turned out to be anchored by virtue of its contents, it cannot be made
- unachored at matching time. Note that setting the option at match time
+ matching position. If a pattern was compiled with PCRE2_ANCHORED, or
+ turned out to be anchored by virtue of its contents, it cannot be made
+ unachored at matching time. Note that setting the option at match time
disables JIT matching.
PCRE2_ENDANCHORED
- If the PCRE2_ENDANCHORED option is set, any string that pcre2_match()
- matches must be right at the end of the subject string. Note that set-
+ If the PCRE2_ENDANCHORED option is set, any string that pcre2_match()
+ matches must be right at the end of the subject string. Note that set-
ting the option at match time disables JIT matching.
PCRE2_NOTBOL
This option specifies that first character of the subject string is not
- the beginning of a line, so the circumflex metacharacter should not
- match before it. Setting this without having set PCRE2_MULTILINE at
+ the beginning of a line, so the circumflex metacharacter should not
+ match before it. Setting this without having set PCRE2_MULTILINE at
compile time causes circumflex never to match. This option affects only
the behaviour of the circumflex metacharacter. It does not affect \A.
@@ -2515,9 +2524,9 @@
PCRE2_NOTEOL
This option specifies that the end of the subject string is not the end
- of a line, so the dollar metacharacter should not match it nor (except
- in multiline mode) a newline immediately before it. Setting this with-
- out having set PCRE2_MULTILINE at compile time causes dollar never to
+ of a line, so the dollar metacharacter should not match it nor (except
+ in multiline mode) a newline immediately before it. Setting this with-
+ out having set PCRE2_MULTILINE at compile time causes dollar never to
match. This option affects only the behaviour of the dollar metacharac-
ter. It does not affect \Z or \z.
@@ -2524,79 +2533,79 @@
PCRE2_NOTEMPTY
An empty string is not considered to be a valid match if this option is
- set. If there are alternatives in the pattern, they are tried. If all
- the alternatives match the empty string, the entire match fails. For
+ set. If there are alternatives in the pattern, they are tried. If all
+ the alternatives match the empty string, the entire match fails. For
example, if the pattern
a?b?
- is applied to a string not beginning with "a" or "b", it matches an
+ is applied to a string not beginning with "a" or "b", it matches an
empty string at the start of the subject. With PCRE2_NOTEMPTY set, this
- match is not valid, so pcre2_match() searches further into the string
+ match is not valid, so pcre2_match() searches further into the string
for occurrences of "a" or "b".
PCRE2_NOTEMPTY_ATSTART
- This is like PCRE2_NOTEMPTY, except that it locks out an empty string
+ This is like PCRE2_NOTEMPTY, except that it locks out an empty string
match only at the first matching position, that is, at the start of the
- subject plus the starting offset. An empty string match later in the
- subject is permitted. If the pattern is anchored, such a match can
+ subject plus the starting offset. An empty string match later in the
+ subject is permitted. If the pattern is anchored, such a match can
occur only if the pattern contains \K.
PCRE2_NO_JIT
- By default, if a pattern has been successfully processed by
- pcre2_jit_compile(), JIT is automatically used when pcre2_match() is
- called with options that JIT supports. Setting PCRE2_NO_JIT disables
+ By default, if a pattern has been successfully processed by
+ pcre2_jit_compile(), JIT is automatically used when pcre2_match() is
+ called with options that JIT supports. Setting PCRE2_NO_JIT disables
the use of JIT; it forces matching to be done by the interpreter.
PCRE2_NO_UTF_CHECK
When PCRE2_UTF is set at compile time, the validity of the subject as a
- UTF string is checked by default when pcre2_match() is subsequently
- called. If a non-zero starting offset is given, the check is applied
- only to that part of the subject that could be inspected during match-
- ing, and there is a check that the starting offset points to the first
- code unit of a character or to the end of the subject. If there are no
- lookbehind assertions in the pattern, the check starts at the starting
- offset. Otherwise, it starts at the length of the longest lookbehind
+ UTF string is checked by default when pcre2_match() is subsequently
+ called. If a non-zero starting offset is given, the check is applied
+ only to that part of the subject that could be inspected during match-
+ ing, and there is a check that the starting offset points to the first
+ code unit of a character or to the end of the subject. If there are no
+ lookbehind assertions in the pattern, the check starts at the starting
+ offset. Otherwise, it starts at the length of the longest lookbehind
before the starting offset, or at the start of the subject if there are
- not that many characters before the starting offset. Note that the
+ not that many characters before the starting offset. Note that the
sequences \b and \B are one-character lookbehinds.
The check is carried out before any other processing takes place, and a
- negative error code is returned if the check fails. There are several
- UTF error codes for each code unit width, corresponding to different
- problems with the code unit sequence. There are discussions about the
- validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the
+ negative error code is returned if the check fails. There are several
+ UTF error codes for each code unit width, corresponding to different
+ problems with the code unit sequence. There are discussions about the
+ validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the
pcre2unicode page.
- If you know that your subject is valid, and you want to skip these
- checks for performance reasons, you can set the PCRE2_NO_UTF_CHECK
- option when calling pcre2_match(). You might want to do this for the
+ If you know that your subject is valid, and you want to skip these
+ checks for performance reasons, you can set the PCRE2_NO_UTF_CHECK
+ option when calling pcre2_match(). You might want to do this for the
second and subsequent calls to pcre2_match() if you are making repeated
calls to find other matches in the same subject string.
- Warning: When PCRE2_NO_UTF_CHECK is set, the effect of passing an
- invalid string as a subject, or an invalid value of startoffset, is
+ Warning: When PCRE2_NO_UTF_CHECK is set, the effect of passing an
+ invalid string as a subject, or an invalid value of startoffset, is
undefined. Your program may crash or loop indefinitely.
PCRE2_PARTIAL_HARD
PCRE2_PARTIAL_SOFT
- These options turn on the partial matching feature. A partial match
- occurs if the end of the subject string is reached successfully, but
- there are not enough subject characters to complete the match. If this
- happens when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set,
- matching continues by testing any remaining alternatives. Only if no
- complete match can be found is PCRE2_ERROR_PARTIAL returned instead of
- PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that
- the caller is prepared to handle a partial match, but only if no com-
+ These options turn on the partial matching feature. A partial match
+ occurs if the end of the subject string is reached successfully, but
+ there are not enough subject characters to complete the match. If this
+ happens when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set,
+ matching continues by testing any remaining alternatives. Only if no
+ complete match can be found is PCRE2_ERROR_PARTIAL returned instead of
+ PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that
+ the caller is prepared to handle a partial match, but only if no com-
plete match can be found.
- If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this
- case, if a partial match is found, pcre2_match() immediately returns
- PCRE2_ERROR_PARTIAL, without considering any other alternatives. In
+ If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this
+ case, if a partial match is found, pcre2_match() immediately returns
+ PCRE2_ERROR_PARTIAL, without considering any other alternatives. In
other words, when PCRE2_PARTIAL_HARD is set, a partial match is consid-
ered to be more important that an alternative complete match.
@@ -2606,38 +2615,38 @@
NEWLINE HANDLING WHEN MATCHING
- When PCRE2 is built, a default newline convention is set; this is usu-
- ally the standard convention for the operating system. The default can
- be overridden in a compile context by calling pcre2_set_newline(). It
- can also be overridden by starting a pattern string with, for example,
- (*CRLF), as described in the section on newline conventions in the
- pcre2pattern page. During matching, the newline choice affects the be-
- haviour of the dot, circumflex, and dollar metacharacters. It may also
- alter the way the match starting position is advanced after a match
+ When PCRE2 is built, a default newline convention is set; this is usu-
+ ally the standard convention for the operating system. The default can
+ be overridden in a compile context by calling pcre2_set_newline(). It
+ can also be overridden by starting a pattern string with, for example,
+ (*CRLF), as described in the section on newline conventions in the
+ pcre2pattern page. During matching, the newline choice affects the be-
+ haviour of the dot, circumflex, and dollar metacharacters. It may also
+ alter the way the match starting position is advanced after a match
failure for an unanchored pattern.
When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is
- set as the newline convention, and a match attempt for an unanchored
+ set as the newline convention, and a match attempt for an unanchored
pattern fails when the current starting position is at a CRLF sequence,
- and the pattern contains no explicit matches for CR or LF characters,
- the match position is advanced by two characters instead of one, in
+ and the pattern contains no explicit matches for CR or LF characters,
+ the match position is advanced by two characters instead of one, in
other words, to after the CRLF.
The above rule is a compromise that makes the most common cases work as
- expected. For example, if the pattern is .+A (and the PCRE2_DOTALL
+ expected. For example, if the pattern is .+A (and the PCRE2_DOTALL
option is not set), it does not match the string "\r\nA" because, after
- failing at the start, it skips both the CR and the LF before retrying.
- However, the pattern [\r\n]A does match that string, because it con-
+ failing at the start, it skips both the CR and the LF before retrying.
+ However, the pattern [\r\n]A does match that string, because it con-
tains an explicit CR or LF reference, and so advances only by one char-
acter after the first failure.
An explicit match for CR of LF is either a literal appearance of one of
- those characters in the pattern, or one of the \r or \n or equivalent
+ those characters in the pattern, or one of the \r or \n or equivalent
octal or hexadecimal escape sequences. Implicit matches such as [^X] do
- not count, nor does \s, even though it includes CR and LF in the char-
+ not count, nor does \s, even though it includes CR and LF in the char-
acters that it matches.
- Notwithstanding the above, anomalous effects may still occur when CRLF
+ Notwithstanding the above, anomalous effects may still occur when CRLF
is a valid newline sequence and explicit \r or \n escapes appear in the
pattern.
@@ -2648,82 +2657,82 @@
PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *match_data);
- In general, a pattern matches a certain portion of the subject, and in
- addition, further substrings from the subject may be picked out by
- parenthesized parts of the pattern. Following the usage in Jeffrey
- Friedl's book, this is called "capturing" in what follows, and the
- phrase "capturing subpattern" or "capturing group" is used for a frag-
- ment of a pattern that picks out a substring. PCRE2 supports several
+ In general, a pattern matches a certain portion of the subject, and in
+ addition, further substrings from the subject may be picked out by
+ parenthesized parts of the pattern. Following the usage in Jeffrey
+ Friedl's book, this is called "capturing" in what follows, and the
+ phrase "capturing subpattern" or "capturing group" is used for a frag-
+ ment of a pattern that picks out a substring. PCRE2 supports several
other kinds of parenthesized subpattern that do not cause substrings to
- be captured. The pcre2_pattern_info() function can be used to find out
+ be captured. The pcre2_pattern_info() function can be used to find out
how many capturing subpatterns there are in a compiled pattern.
- You can use auxiliary functions for accessing captured substrings by
+ You can use auxiliary functions for accessing captured substrings by
number or by name, as described in sections below.
Alternatively, you can make direct use of the vector of PCRE2_SIZE val-
- ues, called the ovector, which contains the offsets of captured
- strings. It is part of the match data block. The function
- pcre2_get_ovector_pointer() returns the address of the ovector, and
+ ues, called the ovector, which contains the offsets of captured
+ strings. It is part of the match data block. The function
+ pcre2_get_ovector_pointer() returns the address of the ovector, and
pcre2_get_ovector_count() returns the number of pairs of values it con-
tains.
Within the ovector, the first in each pair of values is set to the off-
set of the first code unit of a substring, and the second is set to the
- offset of the first code unit after the end of a substring. These val-
- ues are always code unit offsets, not character offsets. That is, they
- are byte offsets in the 8-bit library, 16-bit offsets in the 16-bit
+ offset of the first code unit after the end of a substring. These val-
+ ues are always code unit offsets, not character offsets. That is, they
+ are byte offsets in the 8-bit library, 16-bit offsets in the 16-bit
library, and 32-bit offsets in the 32-bit library.
- After a partial match (error return PCRE2_ERROR_PARTIAL), only the
- first pair of offsets (that is, ovector[0] and ovector[1]) are set.
- They identify the part of the subject that was partially matched. See
+ After a partial match (error return PCRE2_ERROR_PARTIAL), only the
+ first pair of offsets (that is, ovector[0] and ovector[1]) are set.
+ They identify the part of the subject that was partially matched. See
the pcre2partial documentation for details of partial matching.
- After a fully successful match, the first pair of offsets identifies
- the portion of the subject string that was matched by the entire pat-
- tern. The next pair is used for the first captured substring, and so
- on. The value returned by pcre2_match() is one more than the highest
- numbered pair that has been set. For example, if two substrings have
- been captured, the returned value is 3. If there are no captured sub-
+ After a fully successful match, the first pair of offsets identifies
+ the portion of the subject string that was matched by the entire pat-
+ tern. The next pair is used for the first captured substring, and so
+ on. The value returned by pcre2_match() is one more than the highest
+ numbered pair that has been set. For example, if two substrings have
+ been captured, the returned value is 3. If there are no captured sub-
strings, the return value from a successful match is 1, indicating that
just the first pair of offsets has been set.
- If a pattern uses the \K escape sequence within a positive assertion,
+ If a pattern uses the \K escape sequence within a positive assertion,
the reported start of a successful match can be greater than the end of
- the match. For example, if the pattern (?=ab\K) is matched against
+ the match. For example, if the pattern (?=ab\K) is matched against
"ab", the start and end offset values for the match are 2 and 0.
- If a capturing subpattern group is matched repeatedly within a single
- match operation, it is the last portion of the subject that it matched
+ If a capturing subpattern group is matched repeatedly within a single
+ match operation, it is the last portion of the subject that it matched
that is returned.
If the ovector is too small to hold all the captured substring offsets,
- as much as possible is filled in, and the function returns a value of
- zero. If captured substrings are not of interest, pcre2_match() may be
+ as much as possible is filled in, and the function returns a value of
+ zero. If captured substrings are not of interest, pcre2_match() may be
called with a match data block whose ovector is of minimum length (that
is, one pair).
- It is possible for capturing subpattern number n+1 to match some part
+ It is possible for capturing subpattern number n+1 to match some part
of the subject when subpattern n has not been used at all. For example,
- if the string "abc" is matched against the pattern (a|(z))(bc) the
+ if the string "abc" is matched against the pattern (a|(z))(bc) the
return from the function is 4, and subpatterns 1 and 3 are matched, but
- 2 is not. When this happens, both values in the offset pairs corre-
+ 2 is not. When this happens, both values in the offset pairs corre-
sponding to unused subpatterns are set to PCRE2_UNSET.
- Offset values that correspond to unused subpatterns at the end of the
- expression are also set to PCRE2_UNSET. For example, if the string
+ Offset values that correspond to unused subpatterns at the end of the
+ expression are also set to PCRE2_UNSET. For example, if the string
"abc" is matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3
- are not matched. The return from the function is 2, because the high-
+ are not matched. The return from the function is 2, because the high-
est used capturing subpattern number is 1. The offsets for for the sec-
- ond and third capturing subpatterns (assuming the vector is large
+ ond and third capturing subpatterns (assuming the vector is large
enough, of course) are set to PCRE2_UNSET.
Elements in the ovector that do not correspond to capturing parentheses
in the pattern are never changed. That is, if a pattern contains n cap-
turing parentheses, no more than ovector[0] to ovector[2n+1] are set by
- pcre2_match(). The other elements retain whatever values they previ-
- ously had. After a failed match attempt, the contents of the ovector
+ pcre2_match(). The other elements retain whatever values they previ-
+ ously had. After a failed match attempt, the contents of the ovector
are unchanged.
@@ -2733,55 +2742,55 @@
PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *match_data);
- As well as the offsets in the ovector, other information about a match
- is retained in the match data block and can be retrieved by the above
- functions in appropriate circumstances. If they are called at other
+ As well as the offsets in the ovector, other information about a match
+ is retained in the match data block and can be retrieved by the above
+ functions in appropriate circumstances. If they are called at other
times, the result is undefined.
- After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a
+ After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a
failure to match (PCRE2_ERROR_NOMATCH), a (*MARK), (*PRUNE), or (*THEN)
- name may be available. The function pcre2_get_mark() can be called to
- access this name. The same function applies to all three verbs. It
+ name may be available. The function pcre2_get_mark() can be called to
+ access this name. The same function applies to all three verbs. It
returns a pointer to the zero-terminated name, which is within the com-
piled pattern. If no name is available, NULL is returned. The length of
- the name (excluding the terminating zero) is stored in the code unit
- that precedes the name. You should use this length instead of relying
+ the name (excluding the terminating zero) is stored in the code unit
+ that precedes the name. You should use this length instead of relying
on the terminating zero if the name might contain a binary zero.
- After a successful match, the name that is returned is the last
- (*MARK), (*PRUNE), or (*THEN) name encountered on the matching path
- through the pattern. Instances of (*PRUNE) and (*THEN) without names
- are ignored. Thus, for example, if the matching path contains
- (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a
- partial match, the last encountered name is returned. For example,
+ After a successful match, the name that is returned is the last
+ (*MARK), (*PRUNE), or (*THEN) name encountered on the matching path
+ through the pattern. Instances of (*PRUNE) and (*THEN) without names
+ are ignored. Thus, for example, if the matching path contains
+ (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a
+ partial match, the last encountered name is returned. For example,
consider this pattern:
^(*MARK:A)((*MARK:B)a|b)c
- When it matches "bc", the returned name is A. The B mark is "seen" in
- the first branch of the group, but it is not on the matching path. On
- the other hand, when this pattern fails to match "bx", the returned
+ When it matches "bc", the returned name is A. The B mark is "seen" in
+ the first branch of the group, but it is not on the matching path. On
+ the other hand, when this pattern fails to match "bx", the returned
name is B.
- Warning: By default, certain start-of-match optimizations are used to
- give a fast "no match" result in some situations. For example, if the
- anchoring is removed from the pattern above, there is an initial check
- for the presence of "c" in the subject before running the matching
+ Warning: By default, certain start-of-match optimizations are used to
+ give a fast "no match" result in some situations. For example, if the
+ anchoring is removed from the pattern above, there is an initial check
+ for the presence of "c" in the subject before running the matching
engine. This check fails for "bx", causing a match failure without see-
ing any marks. You can disable the start-of-match optimizations by set-
ting the PCRE2_NO_START_OPTIMIZE option for pcre2_compile() or starting
the pattern with (*NO_START_OPT).
- After a successful match, a partial match, or one of the invalid UTF
- errors (for example, PCRE2_ERROR_UTF8_ERR5), pcre2_get_startchar() can
+ After a successful match, a partial match, or one of the invalid UTF
+ errors (for example, PCRE2_ERROR_UTF8_ERR5), pcre2_get_startchar() can
be called. After a successful or partial match it returns the code unit
- offset of the character at which the match started. For a non-partial
- match, this can be different to the value of ovector[0] if the pattern
- contains the \K escape sequence. After a partial match, however, this
- value is always the same as ovector[0] because \K does not affect the
+ offset of the character at which the match started. For a non-partial
+ match, this can be different to the value of ovector[0] if the pattern
+ contains the \K escape sequence. After a partial match, however, this
+ value is always the same as ovector[0] because \K does not affect the
result of a partial match.
- After a UTF check failure, pcre2_get_startchar() can be used to obtain
+ After a UTF check failure, pcre2_get_startchar() can be used to obtain
the code unit offset of the invalid UTF character. Details are given in
the pcre2unicode page.
@@ -2788,14 +2797,14 @@
ERROR RETURNS FROM pcre2_match()
- If pcre2_match() fails, it returns a negative number. This can be con-
- verted to a text string by calling the pcre2_get_error_message() func-
- tion (see "Obtaining a textual error message" below). Negative error
- codes are also returned by other functions, and are documented with
- them. The codes are given names in the header file. If UTF checking is
+ If pcre2_match() fails, it returns a negative number. This can be con-
+ verted to a text string by calling the pcre2_get_error_message() func-
+ tion (see "Obtaining a textual error message" below). Negative error
+ codes are also returned by other functions, and are documented with
+ them. The codes are given names in the header file. If UTF checking is
in force and an invalid UTF subject string is detected, one of a number
- of UTF-specific negative error codes is returned. Details are given in
- the pcre2unicode page. The following are the other errors that may be
+ of UTF-specific negative error codes is returned. Details are given in
+ the pcre2unicode page. The following are the other errors that may be
returned by pcre2_match():
PCRE2_ERROR_NOMATCH
@@ -2804,20 +2813,20 @@
PCRE2_ERROR_PARTIAL
- The subject string did not match, but it did match partially. See the
+ The subject string did not match, but it did match partially. See the
pcre2partial documentation for details of partial matching.
PCRE2_ERROR_BADMAGIC
PCRE2 stores a 4-byte "magic number" at the start of the compiled code,
- to catch the case when it is passed a junk pointer. This is the error
+ to catch the case when it is passed a junk pointer. This is the error
that is returned when the magic number is not present.
PCRE2_ERROR_BADMODE
- This error is given when a compiled pattern is passed to a function in
- a library of a different code unit width, for example, a pattern com-
- piled by the 8-bit library is passed to a 16-bit or 32-bit library
+ This error is given when a compiled pattern is passed to a function in
+ a library of a different code unit width, for example, a pattern com-
+ piled by the 8-bit library is passed to a 16-bit or 32-bit library
function.
PCRE2_ERROR_BADOFFSET
@@ -2831,15 +2840,15 @@
PCRE2_ERROR_BADUTFOFFSET
The UTF code unit sequence that was passed as a subject was checked and
- found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the
- value of startoffset did not point to the beginning of a UTF character
+ found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the
+ value of startoffset did not point to the beginning of a UTF character
or the end of the subject.
PCRE2_ERROR_CALLOUT
- This error is never generated by pcre2_match() itself. It is provided
- for use by callout functions that want to cause pcre2_match() or
- pcre2_callout_enumerate() to return a distinctive error code. See the
+ This error is never generated by pcre2_match() itself. It is provided
+ for use by callout functions that want to cause pcre2_match() or
+ pcre2_callout_enumerate() to return a distinctive error code. See the
pcre2callout documentation for details.
PCRE2_ERROR_DEPTHLIMIT
@@ -2852,14 +2861,14 @@
PCRE2_ERROR_INTERNAL
- An unexpected internal error has occurred. This error could be caused
+ An unexpected internal error has occurred. This error could be caused
by a bug in PCRE2 or by overwriting of the compiled pattern.
PCRE2_ERROR_JIT_STACKLIMIT
- This error is returned when a pattern that was successfully studied
- using JIT is being matched, but the memory available for the just-in-
- time processing stack is not large enough. See the pcre2jit documenta-
+ This error is returned when a pattern that was successfully studied
+ using JIT is being matched, but the memory available for the just-in-
+ time processing stack is not large enough. See the pcre2jit documenta-
tion for more details.
PCRE2_ERROR_MATCHLIMIT
@@ -2868,10 +2877,10 @@
PCRE2_ERROR_NOMEMORY
- If a pattern contains many nested backtracking points, heap memory is
- used to remember them. This error is given when the memory allocation
- function (default or custom) fails. Note that a different error,
- PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds
+ If a pattern contains many nested backtracking points, heap memory is
+ used to remember them. This error is given when the memory allocation
+ function (default or custom) fails. Note that a different error,
+ PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds
the heap limit.
PCRE2_ERROR_NULL
@@ -2880,12 +2889,12 @@
PCRE2_ERROR_RECURSELOOP
- This error is returned when pcre2_match() detects a recursion loop
- within the pattern. Specifically, it means that either the whole pat-
+ This error is returned when pcre2_match() detects a recursion loop
+ within the pattern. Specifically, it means that either the whole pat-
tern or a subpattern has been called recursively for the second time at
- the same position in the subject string. Some simple patterns that
- might do this are detected and faulted at compile time, but more com-
- plicated cases, in particular mutual recursions between two different
+ the same position in the subject string. Some simple patterns that
+ might do this are detected and faulted at compile time, but more com-
+ plicated cases, in particular mutual recursions between two different
subpatterns, cannot be detected until matching is attempted.
@@ -2894,20 +2903,20 @@
int pcre2_get_error_message(int errorcode, PCRE2_UCHAR *buffer,
PCRE2_SIZE bufflen);
- A text message for an error code from any PCRE2 function (compile,
- match, or auxiliary) can be obtained by calling pcre2_get_error_mes-
- sage(). The code is passed as the first argument, with the remaining
- two arguments specifying a code unit buffer and its length in code
- units, into which the text message is placed. The message is returned
- in code units of the appropriate width for the library that is being
+ A text message for an error code from any PCRE2 function (compile,
+ match, or auxiliary) can be obtained by calling pcre2_get_error_mes-
+ sage(). The code is passed as the first argument, with the remaining
+ two arguments specifying a code unit buffer and its length in code
+ units, into which the text message is placed. The message is returned
+ in code units of the appropriate width for the library that is being
used.
- The returned message is terminated with a trailing zero, and the func-
- tion returns the number of code units used, excluding the trailing
+ The returned message is terminated with a trailing zero, and the func-
+ tion returns the number of code units used, excluding the trailing
zero. If the error number is unknown, the negative error code
- PCRE2_ERROR_BADDATA is returned. If the buffer is too small, the mes-
- sage is truncated (but still with a trailing zero), and the negative
- error code PCRE2_ERROR_NOMEMORY is returned. None of the messages are
+ PCRE2_ERROR_BADDATA is returned. If the buffer is too small, the mes-
+ sage is truncated (but still with a trailing zero), and the negative
+ error code PCRE2_ERROR_NOMEMORY is returned. None of the messages are
very long; a buffer size of 120 code units is ample.
@@ -2926,39 +2935,39 @@
void pcre2_substring_free(PCRE2_UCHAR *buffer);
- Captured substrings can be accessed directly by using the ovector as
+ Captured substrings can be accessed directly by using the ovector as
described above. For convenience, auxiliary functions are provided for
- extracting captured substrings as new, separate, zero-terminated
+ extracting captured substrings as new, separate, zero-terminated
strings. A substring that contains a binary zero is correctly extracted
- and has a further zero added on the end, but the result is not, of
+ and has a further zero added on the end, but the result is not, of
course, a C string.
The functions in this section identify substrings by number. The number
zero refers to the entire matched substring, with higher numbers refer-
- ring to substrings captured by parenthesized groups. After a partial
- match, only substring zero is available. An attempt to extract any
- other substring gives the error PCRE2_ERROR_PARTIAL. The next section
+ ring to substrings captured by parenthesized groups. After a partial
+ match, only substring zero is available. An attempt to extract any
+ other substring gives the error PCRE2_ERROR_PARTIAL. The next section
describes similar functions for extracting captured substrings by name.
- If a pattern uses the \K escape sequence within a positive assertion,
+ If a pattern uses the \K escape sequence within a positive assertion,
the reported start of a successful match can be greater than the end of
- the match. For example, if the pattern (?=ab\K) is matched against
- "ab", the start and end offset values for the match are 2 and 0. In
- this situation, calling these functions with a zero substring number
+ the match. For example, if the pattern (?=ab\K) is matched against
+ "ab", the start and end offset values for the match are 2 and 0. In
+ this situation, calling these functions with a zero substring number
extracts a zero-length empty string.
- You can find the length in code units of a captured substring without
- extracting it by calling pcre2_substring_length_bynumber(). The first
- argument is a pointer to the match data block, the second is the group
- number, and the third is a pointer to a variable into which the length
- is placed. If you just want to know whether or not the substring has
+ You can find the length in code units of a captured substring without
+ extracting it by calling pcre2_substring_length_bynumber(). The first
+ argument is a pointer to the match data block, the second is the group
+ number, and the third is a pointer to a variable into which the length
+ is placed. If you just want to know whether or not the substring has
been captured, you can pass the third argument as NULL.
- The pcre2_substring_copy_bynumber() function copies a captured sub-
- string into a supplied buffer, whereas pcre2_substring_get_bynumber()
- copies it into new memory, obtained using the same memory allocation
- function that was used for the match data block. The first two argu-
- ments of these functions are a pointer to the match data block and a
+ The pcre2_substring_copy_bynumber() function copies a captured sub-
+ string into a supplied buffer, whereas pcre2_substring_get_bynumber()
+ copies it into new memory, obtained using the same memory allocation
+ function that was used for the match data block. The first two argu-
+ ments of these functions are a pointer to the match data block and a
capturing group number.
The final arguments of pcre2_substring_copy_bynumber() are a pointer to
@@ -2967,25 +2976,25 @@
for the extracted substring, excluding the terminating zero.
For pcre2_substring_get_bynumber() the third and fourth arguments point
- to variables that are updated with a pointer to the new memory and the
- number of code units that comprise the substring, again excluding the
- terminating zero. When the substring is no longer needed, the memory
+ to variables that are updated with a pointer to the new memory and the
+ number of code units that comprise the substring, again excluding the
+ terminating zero. When the substring is no longer needed, the memory
should be freed by calling pcre2_substring_free().
- The return value from all these functions is zero for success, or a
- negative error code. If the pattern match failed, the match failure
- code is returned. If a substring number greater than zero is used
- after a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible
+ The return value from all these functions is zero for success, or a
+ negative error code. If the pattern match failed, the match failure
+ code is returned. If a substring number greater than zero is used
+ after a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible
error codes are:
PCRE2_ERROR_NOMEMORY
- The buffer was too small for pcre2_substring_copy_bynumber(), or the
+ The buffer was too small for pcre2_substring_copy_bynumber(), or the
attempt to get memory failed for pcre2_substring_get_bynumber().
PCRE2_ERROR_NOSUBSTRING
- There is no substring with that number in the pattern, that is, the
+ There is no substring with that number in the pattern, that is, the
number is greater than the number of capturing parentheses.
PCRE2_ERROR_UNAVAILABLE
@@ -2996,8 +3005,8 @@
PCRE2_ERROR_UNSET
- The substring did not participate in the match. For example, if the
- pattern is (abc)|(def) and the subject is "def", and the ovector con-
+ The substring did not participate in the match. For example, if the
+ pattern is (abc)|(def) and the subject is "def", and the ovector con-
tains at least two capturing slots, substring number 1 is unset.
@@ -3008,32 +3017,32 @@
void pcre2_substring_list_free(PCRE2_SPTR *list);
- The pcre2_substring_list_get() function extracts all available sub-
- strings and builds a list of pointers to them. It also (optionally)
- builds a second list that contains their lengths (in code units),
+ The pcre2_substring_list_get() function extracts all available sub-
+ strings and builds a list of pointers to them. It also (optionally)
+ builds a second list that contains their lengths (in code units),
excluding a terminating zero that is added to each of them. All this is
done in a single block of memory that is obtained using the same memory
allocation function that was used to get the match data block.
- This function must be called only after a successful match. If called
+ This function must be called only after a successful match. If called
after a partial match, the error code PCRE2_ERROR_PARTIAL is returned.
- The address of the memory block is returned via listptr, which is also
+ The address of the memory block is returned via listptr, which is also
the start of the list of string pointers. The end of the list is marked
- by a NULL pointer. The address of the list of lengths is returned via
- lengthsptr. If your strings do not contain binary zeros and you do not
+ by a NULL pointer. The address of the list of lengths is returned via
+ lengthsptr. If your strings do not contain binary zeros and you do not
therefore need the lengths, you may supply NULL as the lengthsptr argu-
- ment to disable the creation of a list of lengths. The yield of the
- function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem-
- ory block could not be obtained. When the list is no longer needed, it
+ ment to disable the creation of a list of lengths. The yield of the
+ function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem-
+ ory block could not be obtained. When the list is no longer needed, it
should be freed by calling pcre2_substring_list_free().
If this function encounters a substring that is unset, which can happen
- when capturing subpattern number n+1 matches some part of the subject,
- but subpattern n has not been used at all, it returns an empty string.
- This can be distinguished from a genuine zero-length substring by
+ when capturing subpattern number n+1 matches some part of the subject,
+ but subpattern n has not been used at all, it returns an empty string.
+ This can be distinguished from a genuine zero-length substring by
inspecting the appropriate offset in the ovector, which contain
- PCRE2_UNSET for unset substrings, or by calling pcre2_sub-
+ PCRE2_UNSET for unset substrings, or by calling pcre2_sub-
string_length_bynumber().
@@ -3053,39 +3062,39 @@
void pcre2_substring_free(PCRE2_UCHAR *buffer);
- To extract a substring by name, you first have to find associated num-
+ To extract a substring by name, you first have to find associated num-
ber. For example, for this pattern:
(a+)b(?<xxx>\d+)...
the number of the subpattern called "xxx" is 2. If the name is known to
- be unique (PCRE2_DUPNAMES was not set), you can find the number from
+ be unique (PCRE2_DUPNAMES was not set), you can find the number from
the name by calling pcre2_substring_number_from_name(). The first argu-
- ment is the compiled pattern, and the second is the name. The yield of
+ ment is the compiled pattern, and the second is the name. The yield of
the function is the subpattern number, PCRE2_ERROR_NOSUBSTRING if there
- is no subpattern of that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if
- there is more than one subpattern of that name. Given the number, you
- can extract the substring directly from the ovector, or use one of the
+ is no subpattern of that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if
+ there is more than one subpattern of that name. Given the number, you
+ can extract the substring directly from the ovector, or use one of the
"bynumber" functions described above.
- For convenience, there are also "byname" functions that correspond to
- the "bynumber" functions, the only difference being that the second
- argument is a name instead of a number. If PCRE2_DUPNAMES is set and
+ For convenience, there are also "byname" functions that correspond to
+ the "bynumber" functions, the only difference being that the second
+ argument is a name instead of a number. If PCRE2_DUPNAMES is set and
there are duplicate names, these functions scan all the groups with the
given name, and return the first named string that is set.
- If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
- returned. If all groups with the name have numbers that are greater
- than the number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is
- returned. If there is at least one group with a slot in the ovector,
+ If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is
+ returned. If all groups with the name have numbers that are greater
+ than the number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is
+ returned. If there is at least one group with a slot in the ovector,
but no group is found to be set, PCRE2_ERROR_UNSET is returned.
Warning: If the pattern uses the (?| feature to set up multiple subpat-
- terns with the same number, as described in the section on duplicate
- subpattern numbers in the pcre2pattern page, you cannot use names to
- distinguish the different subpatterns, because names are not included
- in the compiled code. The matching process uses only numbers. For this
- reason, the use of different names for subpatterns of the same number
+ terns with the same number, as described in the section on duplicate
+ subpattern numbers in the pcre2pattern page, you cannot use names to
+ distinguish the different subpatterns, because names are not included
+ in the compiled code. The matching process uses only numbers. For this
+ reason, the use of different names for subpatterns of the same number
causes an error at compile time.
@@ -3098,54 +3107,54 @@
PCRE2_SIZE rlength, PCRE2_UCHAR *outputbuffer,
PCRE2_SIZE *outlengthptr);
- This function calls pcre2_match() and then makes a copy of the subject
- string in outputbuffer, replacing one or more parts that were matched
+ This function calls pcre2_match() and then makes a copy of the subject
+ string in outputbuffer, replacing one or more parts that were matched
with the replacement string, whose length is supplied in rlength. This
- can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string.
- The default is to perform just one replacement, but there is an option
- that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below
+ can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string.
+ The default is to perform just one replacement, but there is an option
+ that requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below
for details).
- Matches in which a \K item in a lookahead in the pattern causes the
- match to end before it starts are not supported, and give rise to an
+ Matches in which a \K item in a lookahead in the pattern causes the
+ match to end before it starts are not supported, and give rise to an
error return. For global replacements, matches in which \K in a lookbe-
- hind causes the match to start earlier than the point that was reached
+ hind causes the match to start earlier than the point that was reached
in the previous iteration are also not supported.
- The first seven arguments of pcre2_substitute() are the same as for
+ The first seven arguments of pcre2_substitute() are the same as for
pcre2_match(), except that the partial matching options are not permit-
- ted, and match_data may be passed as NULL, in which case a match data
- block is obtained and freed within this function, using memory manage-
- ment functions from the match context, if provided, or else those that
+ ted, and match_data may be passed as NULL, in which case a match data
+ block is obtained and freed within this function, using memory manage-
+ ment functions from the match context, if provided, or else those that
were used to allocate memory for the compiled code.
- If an external match_data block is provided, its contents afterwards
- are those set by the final call to pcre2_match(). For global changes,
- this will have ended in a matching error. The contents of the ovector
+ If an external match_data block is provided, its contents afterwards
+ are those set by the final call to pcre2_match(). For global changes,
+ this will have ended in a matching error. The contents of the ovector
within the match data block may or may not have been changed.
- The outlengthptr argument must point to a variable that contains the
- length, in code units, of the output buffer. If the function is suc-
- cessful, the value is updated to contain the length of the new string,
+ The outlengthptr argument must point to a variable that contains the
+ length, in code units, of the output buffer. If the function is suc-
+ cessful, the value is updated to contain the length of the new string,
excluding the trailing zero that is automatically added.
- If the function is not successful, the value set via outlengthptr
- depends on the type of error. For syntax errors in the replacement
- string, the value is the offset in the replacement string where the
- error was detected. For other errors, the value is PCRE2_UNSET by
- default. This includes the case of the output buffer being too small,
- unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set (see below), in which
- case the value is the minimum length needed, including space for the
- trailing zero. Note that in order to compute the required length,
- pcre2_substitute() has to simulate all the matching and copying,
+ If the function is not successful, the value set via outlengthptr
+ depends on the type of error. For syntax errors in the replacement
+ string, the value is the offset in the replacement string where the
+ error was detected. For other errors, the value is PCRE2_UNSET by
+ default. This includes the case of the output buffer being too small,
+ unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set (see below), in which
+ case the value is the minimum length needed, including space for the
+ trailing zero. Note that in order to compute the required length,
+ pcre2_substitute() has to simulate all the matching and copying,
instead of giving an error return as soon as the buffer overflows. Note
also that the length is in code units, not bytes.
- In the replacement string, which is interpreted as a UTF string in UTF
- mode, and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK
+ In the replacement string, which is interpreted as a UTF string in UTF
+ mode, and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK
option is set, a dollar character is an escape character that can spec-
- ify the insertion of characters from capturing groups or names from
- (*MARK) or other control verbs in the pattern. The following forms are
+ ify the insertion of characters from capturing groups or names from
+ (*MARK) or other control verbs in the pattern. The following forms are
always recognized:
$$ insert a dollar character
@@ -3152,19 +3161,19 @@
$<n> or ${<n>} insert the contents of group <n>
$*MARK or ${*MARK} insert a control verb name
- Either a group number or a group name can be given for <n>. Curly
- brackets are required only if the following character would be inter-
+ Either a group number or a group name can be given for <n>. Curly
+ brackets are required only if the following character would be inter-
preted as part of the number or name. The number may be zero to include
- the entire matched string. For example, if the pattern a(b)c is
- matched with "=abc=" and the replacement string "+$1$0$1+", the result
+ the entire matched string. For example, if the pattern a(b)c is
+ matched with "=abc=" and the replacement string "+$1$0$1+", the result
is "=+babcb+=".
$*MARK inserts the name from the last encountered (*ACCEPT), (*COMMIT),
- (*MARK), (*PRUNE), or (*THEN) on the matching path that has a name.
- (*MARK) must always include a name, but the other verbs need not. For
+ (*MARK), (*PRUNE), or (*THEN) on the matching path that has a name.
+ (*MARK) must always include a name, but the other verbs need not. For
example, in the case of (*MARK:A)(*PRUNE) the name inserted is "A", but
- for (*MARK:A)(*PRUNE:B) the relevant name is "B". This facility can be
- used to perform simple simultaneous substitutions, as this pcre2test
+ for (*MARK:A)(*PRUNE:B) the relevant name is "B". This facility can be
+ used to perform simple simultaneous substitutions, as this pcre2test
example shows:
/(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
@@ -3171,19 +3180,19 @@
apple lemon
2: pear orange
- As well as the usual options for pcre2_match(), a number of additional
+ As well as the usual options for pcre2_match(), a number of additional
options can be set in the options argument of pcre2_substitute().
PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
- string, replacing every matching substring. If this option is not set,
- only the first matching substring is replaced. The search for matches
- takes place in the original subject string (that is, previous replace-
- ments do not affect it). Iteration is implemented by advancing the
- startoffset value for each search, which is always passed the entire
+ string, replacing every matching substring. If this option is not set,
+ only the first matching substring is replaced. The search for matches
+ takes place in the original subject string (that is, previous replace-
+ ments do not affect it). Iteration is implemented by advancing the
+ startoffset value for each search, which is always passed the entire
subject string. If an offset limit is set in the match context, search-
ing stops when that limit is reached.
- You can restrict the effect of a global substitution to a portion of
+ You can restrict the effect of a global substitution to a portion of
the subject string by setting either or both of startoffset and an off-
set limit. Here is a pcre2test example:
@@ -3191,87 +3200,87 @@
ABC ABC ABC ABC\=offset=3,offset_limit=12
2: ABC A!C A!C ABC
- When continuing with global substitutions after matching a substring
+ When continuing with global substitutions after matching a substring
with zero length, an attempt to find a non-empty match at the same off-
set is performed. If this is not successful, the offset is advanced by
one character except when CRLF is a valid newline sequence and the next
- two characters are CR, LF. In this case, the offset is advanced by two
+ two characters are CR, LF. In this case, the offset is advanced by two
characters.
- PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
+ PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output
buffer is too small. The default action is to return PCRE2_ERROR_NOMEM-
- ORY immediately. If this option is set, however, pcre2_substitute()
+ ORY immediately. If this option is set, however, pcre2_substitute()
continues to go through the motions of matching and substituting (with-
- out, of course, writing anything) in order to compute the size of buf-
- fer that is needed. This value is passed back via the outlengthptr
- variable, with the result of the function still being
+ out, of course, writing anything) in order to compute the size of buf-
+ fer that is needed. This value is passed back via the outlengthptr
+ variable, with the result of the function still being
PCRE2_ERROR_NOMEMORY.
- Passing a buffer size of zero is a permitted way of finding out how
- much memory is needed for given substitution. However, this does mean
+ Passing a buffer size of zero is a permitted way of finding out how
+ much memory is needed for given substitution. However, this does mean
that the entire operation is carried out twice. Depending on the appli-
- cation, it may be more efficient to allocate a large buffer and free
- the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER-
+ cation, it may be more efficient to allocate a large buffer and free
+ the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER-
FLOW_LENGTH.
- PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capturing groups
- that do not appear in the pattern to be treated as unset groups. This
- option should be used with care, because it means that a typo in a
- group name or number no longer causes the PCRE2_ERROR_NOSUBSTRING
+ PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capturing groups
+ that do not appear in the pattern to be treated as unset groups. This
+ option should be used with care, because it means that a typo in a
+ group name or number no longer causes the PCRE2_ERROR_NOSUBSTRING
error.
- PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capturing groups (including
+ PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capturing groups (including
unknown groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be
- treated as empty strings when inserted as described above. If this
- option is not set, an attempt to insert an unset group causes the
- PCRE2_ERROR_UNSET error. This option does not influence the extended
+ treated as empty strings when inserted as described above. If this
+ option is not set, an attempt to insert an unset group causes the
+ PCRE2_ERROR_UNSET error. This option does not influence the extended
substitution syntax described below.
- PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
- replacement string. Without this option, only the dollar character is
- special, and only the group insertion forms listed above are valid.
+ PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the
+ replacement string. Without this option, only the dollar character is
+ special, and only the group insertion forms listed above are valid.
When PCRE2_SUBSTITUTE_EXTENDED is set, two things change:
- Firstly, backslash in a replacement string is interpreted as an escape
+ Firstly, backslash in a replacement string is interpreted as an escape
character. The usual forms such as \n or \x{ddd} can be used to specify
- particular character codes, and backslash followed by any non-alphanu-
- meric character quotes that character. Extended quoting can be coded
+ particular character codes, and backslash followed by any non-alphanu-
+ meric character quotes that character. Extended quoting can be coded
using \Q...\E, exactly as in pattern strings.
- There are also four escape sequences for forcing the case of inserted
- letters. The insertion mechanism has three states: no case forcing,
+ There are also four escape sequences for forcing the case of inserted
+ letters. The insertion mechanism has three states: no case forcing,
force upper case, and force lower case. The escape sequences change the
current state: \U and \L change to upper or lower case forcing, respec-
- tively, and \E (when not terminating a \Q quoted sequence) reverts to
- no case forcing. The sequences \u and \l force the next character (if
- it is a letter) to upper or lower case, respectively, and then the
+ tively, and \E (when not terminating a \Q quoted sequence) reverts to
+ no case forcing. The sequences \u and \l force the next character (if
+ it is a letter) to upper or lower case, respectively, and then the
state automatically reverts to no case forcing. Case forcing applies to
all inserted characters, including those from captured groups and let-
ters within \Q...\E quoted sequences.
Note that case forcing sequences such as \U...\E do not nest. For exam-
- ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
+ ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
\E has no effect.
- The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
- flexibility to group substitution. The syntax is similar to that used
+ The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
+ flexibility to group substitution. The syntax is similar to that used
by Bash:
${<n>:-<string>}
${<n>:+<string1>:<string2>}
- As before, <n> may be a group number or a name. The first form speci-
- fies a default value. If group <n> is set, its value is inserted; if
- not, <string> is expanded and the result inserted. The second form
- specifies strings that are expanded and inserted when group <n> is set
- or unset, respectively. The first form is just a convenient shorthand
+ As before, <n> may be a group number or a name. The first form speci-
+ fies a default value. If group <n> is set, its value is inserted; if
+ not, <string> is expanded and the result inserted. The second form
+ specifies strings that are expanded and inserted when group <n> is set
+ or unset, respectively. The first form is just a convenient shorthand
for
${<n>:+${<n>}:<string>}
- Backslash can be used to escape colons and closing curly brackets in
- the replacement strings. A change of the case forcing state within a
- replacement string remains in force afterwards, as shown in this
+ Backslash can be used to escape colons and closing curly brackets in
+ the replacement strings. A change of the case forcing state within a
+ replacement string remains in force afterwards, as shown in this
pcre2test example:
/(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
@@ -3280,16 +3289,16 @@
somebody
1: HELLO
- The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
- substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause
+ The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
+ substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause
unknown groups in the extended syntax forms to be treated as unset.
- If successful, pcre2_substitute() returns the number of replacements
+ If successful, pcre2_substitute() returns the number of replacements
that were made. This may be zero if no matches were found, and is never
greater than 1 unless PCRE2_SUBSTITUTE_GLOBAL is set.
In the event of an error, a negative error code is returned. Except for
- PCRE2_ERROR_NOMATCH (which is never returned), errors from
+ PCRE2_ERROR_NOMATCH (which is never returned), errors from
pcre2_match() are passed straight back.
PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser-
@@ -3296,26 +3305,26 @@
tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.
PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ-
- ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
+ ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
when the simple (non-extended) syntax is used and PCRE2_SUBSTI-
TUTE_UNSET_EMPTY is not set.
- PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
+ PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big
enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size
- of buffer that is needed is returned via outlengthptr. Note that this
+ of buffer that is needed is returned via outlengthptr. Note that this
does not happen by default.
- PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
+ PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in
the replacement string, with more particular errors being
- PCRE2_ERROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REP-
- MISSINGBRACE (closing curly bracket not found), PCRE2_ERROR_BADSUBSTI-
+ PCRE2_ERROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REP-
+ MISSINGBRACE (closing curly bracket not found), PCRE2_ERROR_BADSUBSTI-
TUTION (syntax error in extended group substitution), and
- PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before it started
- or the match started earlier than the current position in the subject,
+ PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before it started
+ or the match started earlier than the current position in the subject,
which can happen if \K is used in an assertion).
As for all PCRE2 errors, a text message that describes the error can be
- obtained by calling the pcre2_get_error_message() function (see
+ obtained by calling the pcre2_get_error_message() function (see
"Obtaining a textual error message" above).
Substitution callouts
@@ -3324,15 +3333,15 @@
void (*callout_function)(pcre2_substitute_callout_block *, void *),
void *callout_data);
- The pcre2_set_substitution_callout() function can be used to specify a
- callout function for pcre2_substitute(). This information is passed in
- a match context. The callout function is called after each substitu-
- tion. It is not called for simulated substitutions that happen as a
- result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. A callout func-
+ The pcre2_set_substitution_callout() function can be used to specify a
+ callout function for pcre2_substitute(). This information is passed in
+ a match context. The callout function is called after each substitu-
+ tion. It is not called for simulated substitutions that happen as a
+ result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option. A callout func-
tion should not return any value.
The first argument of the callout function is a pointer to a substitute
- callout block structure, which contains the following fields, not nec-
+ callout block structure, which contains the following fields, not nec-
essarily in this order:
uint32_t version;
@@ -3339,16 +3348,16 @@
PCRE2_SIZE input_offsets[2];
PCRE2_SIZE output_offsets[2];
- The version field contains the version number of the block format. The
- current version is 0. The version number will increase in future if
- more fields are added, but the intention is never to remove any of the
+ The version field contains the version number of the block format. The
+ current version is 0. The version number will increase in future if
+ more fields are added, but the intention is never to remove any of the
existing fields.
- The input_offsets vector contains the code unit offsets in the input
+ The input_offsets vector contains the code unit offsets in the input
string of the matched substring, and the output_offsets vector contains
the offsets of the replacement in the output string.
- The second argument of the callout function is the value passed as
+ The second argument of the callout function is the value passed as
callout_data when the function was registered.
@@ -3357,56 +3366,56 @@
int pcre2_substring_nametable_scan(const pcre2_code *code,
PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);
- When a pattern is compiled with the PCRE2_DUPNAMES option, names for
- subpatterns are not required to be unique. Duplicate names are always
- allowed for subpatterns with the same number, created by using the (?|
- feature. Indeed, if such subpatterns are named, they are required to
+ When a pattern is compiled with the PCRE2_DUPNAMES option, names for
+ subpatterns are not required to be unique. Duplicate names are always
+ allowed for subpatterns with the same number, created by using the (?|
+ feature. Indeed, if such subpatterns are named, they are required to
use the same names.
Normally, patterns with duplicate names are such that in any one match,
- only one of the named subpatterns participates. An example is shown in
+ only one of the named subpatterns participates. An example is shown in
the pcre2pattern documentation.
- When duplicates are present, pcre2_substring_copy_byname() and
- pcre2_substring_get_byname() return the first substring corresponding
- to the given name that is set. Only if none are set is
- PCRE2_ERROR_UNSET is returned. The pcre2_substring_number_from_name()
+ When duplicates are present, pcre2_substring_copy_byname() and
+ pcre2_substring_get_byname() return the first substring corresponding
+ to the given name that is set. Only if none are set is
+ PCRE2_ERROR_UNSET is returned. The pcre2_substring_number_from_name()
function returns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are
duplicate names.
- If you want to get full details of all captured substrings for a given
- name, you must use the pcre2_substring_nametable_scan() function. The
- first argument is the compiled pattern, and the second is the name. If
- the third and fourth arguments are NULL, the function returns a group
+ If you want to get full details of all captured substrings for a given
+ name, you must use the pcre2_substring_nametable_scan() function. The
+ first argument is the compiled pattern, and the second is the name. If
+ the third and fourth arguments are NULL, the function returns a group
number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.
When the third and fourth arguments are not NULL, they must be pointers
- to variables that are updated by the function. After it has run, they
+ to variables that are updated by the function. After it has run, they
point to the first and last entries in the name-to-number table for the
- given name, and the function returns the length of each entry in code
- units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
+ given name, and the function returns the length of each entry in code
+ units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
no entries for the given name.
The format of the name table is described above in the section entitled
- Information about a pattern. Given all the relevant entries for the
- name, you can extract each of their numbers, and hence the captured
+ Information about a pattern. Given all the relevant entries for the
+ name, you can extract each of their numbers, and hence the captured
data.
FINDING ALL POSSIBLE MATCHES AT ONE POSITION
- The traditional matching function uses a similar algorithm to Perl,
- which stops when it finds the first match at a given point in the sub-
+ The traditional matching function uses a similar algorithm to Perl,
+ which stops when it finds the first match at a given point in the sub-
ject. If you want to find all possible matches, or the longest possible
- match at a given position, consider using the alternative matching
- function (see below) instead. If you cannot use the alternative func-
+ match at a given position, consider using the alternative matching
+ function (see below) instead. If you cannot use the alternative func-
tion, you can kludge it up by making use of the callout facility, which
is described in the pcre2callout documentation.
What you have to do is to insert a callout right at the end of the pat-
- tern. When your callout function is called, extract and save the cur-
- rent matched substring. Then return 1, which forces pcre2_match() to
- backtrack and try other alternatives. Ultimately, when it runs out of
+ tern. When your callout function is called, extract and save the cur-
+ rent matched substring. Then return 1, which forces pcre2_match() to
+ backtrack and try other alternatives. Ultimately, when it runs out of
matches, pcre2_match() will yield PCRE2_ERROR_NOMATCH.
@@ -3418,26 +3427,26 @@
pcre2_match_context *mcontext,
int *workspace, PCRE2_SIZE wscount);
- The function pcre2_dfa_match() is called to match a subject string
- against a compiled pattern, using a matching algorithm that scans the
+ The function pcre2_dfa_match() is called to match a subject string
+ against a compiled pattern, using a matching algorithm that scans the
subject string just once (not counting lookaround assertions), and does
- not backtrack. This has different characteristics to the normal algo-
- rithm, and is not compatible with Perl. Some of the features of PCRE2
- patterns are not supported. Nevertheless, there are times when this
- kind of matching can be useful. For a discussion of the two matching
+ not backtrack. This has different characteristics to the normal algo-
+ rithm, and is not compatible with Perl. Some of the features of PCRE2
+ patterns are not supported. Nevertheless, there are times when this
+ kind of matching can be useful. For a discussion of the two matching
algorithms, and a list of features that pcre2_dfa_match() does not sup-
port, see the pcre2matching documentation.
- The arguments for the pcre2_dfa_match() function are the same as for
+ The arguments for the pcre2_dfa_match() function are the same as for
pcre2_match(), plus two extras. The ovector within the match data block
is used in a different way, and this is described below. The other com-
- mon arguments are used in the same way as for pcre2_match(), so their
+ mon arguments are used in the same way as for pcre2_match(), so their
description is not repeated here.
- The two additional arguments provide workspace for the function. The
- workspace vector should contain at least 20 elements. It is used for
+ The two additional arguments provide workspace for the function. The
+ workspace vector should contain at least 20 elements. It is used for
keeping track of multiple paths through the pattern tree. More
- workspace is needed for patterns and subjects where there are a lot of
+ workspace is needed for patterns and subjects where there are a lot of
potential matches.
Here is an example of a simple call to pcre2_dfa_match():
@@ -3457,45 +3466,45 @@
Option bits for pcre_dfa_match()
- The unused bits of the options argument for pcre2_dfa_match() must be
- zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDAN-
- CHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY,
+ The unused bits of the options argument for pcre2_dfa_match() must be
+ zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDAN-
+ CHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY,
PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD,
- PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but
- the last four of these are exactly the same as for pcre2_match(), so
+ PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but
+ the last four of these are exactly the same as for pcre2_match(), so
their description is not repeated here.
PCRE2_PARTIAL_HARD
PCRE2_PARTIAL_SOFT
- These have the same general effect as they do for pcre2_match(), but
- the details are slightly different. When PCRE2_PARTIAL_HARD is set for
- pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
+ These have the same general effect as they do for pcre2_match(), but
+ the details are slightly different. When PCRE2_PARTIAL_HARD is set for
+ pcre2_dfa_match(), it returns PCRE2_ERROR_PARTIAL if the end of the
subject is reached and there is still at least one matching possibility
that requires additional characters. This happens even if some complete
- matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
- return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
- if the end of the subject is reached, there have been no complete
+ matches have already been found. When PCRE2_PARTIAL_SOFT is set, the
+ return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
+ if the end of the subject is reached, there have been no complete
matches, but there is still at least one matching possibility. The por-
- tion of the string that was inspected when the longest partial match
+ tion of the string that was inspected when the longest partial match
was found is set as the first matching string in both cases. There is a
- more detailed discussion of partial and multi-segment matching, with
+ more detailed discussion of partial and multi-segment matching, with
examples, in the pcre2partial documentation.
PCRE2_DFA_SHORTEST
- Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
+ Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to
stop as soon as it has found one match. Because of the way the alterna-
- tive algorithm works, this is necessarily the shortest possible match
+ tive algorithm works, this is necessarily the shortest possible match
at the first possible matching point in the subject string.
PCRE2_DFA_RESTART
- When pcre2_dfa_match() returns a partial match, it is possible to call
+ When pcre2_dfa_match() returns a partial match, it is possible to call
it again, with additional subject characters, and have it continue with
the same match. The PCRE2_DFA_RESTART option requests this action; when
- it is set, the workspace and wscount options must reference the same
- vector as before because data about the match so far is left in them
+ it is set, the workspace and wscount options must reference the same
+ vector as before because data about the match so far is left in them
after a partial match. There is more discussion of this facility in the
pcre2partial documentation.
@@ -3503,8 +3512,8 @@
When pcre2_dfa_match() succeeds, it may have matched more than one sub-
string in the subject. Note, however, that all the matches from one run
- of the function start at the same point in the subject. The shorter
- matches are all initial substrings of the longer matches. For example,
+ of the function start at the same point in the subject. The shorter
+ matches are all initial substrings of the longer matches. For example,
if the pattern
<.*>
@@ -3519,73 +3528,73 @@
<something> <something else>
<something>
- On success, the yield of the function is a number greater than zero,
- which is the number of matched substrings. The offsets of the sub-
- strings are returned in the ovector, and can be extracted by number in
- the same way as for pcre2_match(), but the numbers bear no relation to
- any capturing groups that may exist in the pattern, because DFA match-
+ On success, the yield of the function is a number greater than zero,
+ which is the number of matched substrings. The offsets of the sub-
+ strings are returned in the ovector, and can be extracted by number in
+ the same way as for pcre2_match(), but the numbers bear no relation to
+ any capturing groups that may exist in the pattern, because DFA match-
ing does not support group capture.
- Calls to the convenience functions that extract substrings by name
- return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used
+ Calls to the convenience functions that extract substrings by name
+ return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used
after a DFA match. The convenience functions that extract substrings by
number never return PCRE2_ERROR_NOSUBSTRING.
- The matched strings are stored in the ovector in reverse order of
- length; that is, the longest matching string is first. If there were
- too many matches to fit into the ovector, the yield of the function is
+ The matched strings are stored in the ovector in reverse order of
+ length; that is, the longest matching string is first. If there were
+ too many matches to fit into the ovector, the yield of the function is
zero, and the vector is filled with the longest matches.
- NOTE: PCRE2's "auto-possessification" optimization usually applies to
- character repeats at the end of a pattern (as well as internally). For
- example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
- matching, this means that only one possible match is found. If you
- really do want multiple matches in such cases, either use an ungreedy
- repeat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when
+ NOTE: PCRE2's "auto-possessification" optimization usually applies to
+ character repeats at the end of a pattern (as well as internally). For
+ example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA
+ matching, this means that only one possible match is found. If you
+ really do want multiple matches in such cases, either use an ungreedy
+ repeat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when
compiling.
Error returns from pcre2_dfa_match()
The pcre2_dfa_match() function returns a negative number when it fails.
- Many of the errors are the same as for pcre2_match(), as described
+ Many of the errors are the same as for pcre2_match(), as described
above. There are in addition the following errors that are specific to
pcre2_dfa_match():
PCRE2_ERROR_DFA_UITEM
- This return is given if pcre2_dfa_match() encounters an item in the
- pattern that it does not support, for instance, the use of \C in a UTF
+ This return is given if pcre2_dfa_match() encounters an item in the
+ pattern that it does not support, for instance, the use of \C in a UTF
mode or a backreference.
PCRE2_ERROR_DFA_UCOND
- This return is given if pcre2_dfa_match() encounters a condition item
+ This return is given if pcre2_dfa_match() encounters a condition item
that uses a backreference for the condition, or a test for recursion in
a specific group. These are not supported.
PCRE2_ERROR_DFA_WSSIZE
- This return is given if pcre2_dfa_match() runs out of space in the
+ This return is given if pcre2_dfa_match() runs out of space in the
workspace vector.
PCRE2_ERROR_DFA_RECURSE
- When a recursive subpattern is processed, the matching function calls
+ When a recursive subpattern is processed, the matching function calls
itself recursively, using private memory for the ovector and workspace.
- This error is given if the internal ovector is not large enough. This
+ This error is given if the internal ovector is not large enough. This
should be extremely rare, as a vector of size 1000 is used.
PCRE2_ERROR_DFA_BADRESTART
- When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
- some plausibility checks are made on the contents of the workspace,
- which should contain data about the previous partial match. If any of
+ When pcre2_dfa_match() is called with the PCRE2_DFA_RESTART option,
+ some plausibility checks are made on the contents of the workspace,
+ which should contain data about the previous partial match. If any of
these checks fail, this error is given.
SEE ALSO
- pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
+ pcre2build(3), pcre2callout(3), pcre2demo(3), pcre2matching(3),
pcre2partial(3), pcre2posix(3), pcre2sample(3), pcre2unicode(3).
@@ -3598,7 +3607,7 @@
REVISION
- Last updated: 18 September 2018
+ Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
------------------------------------------------------------------------------
@@ -6247,7 +6256,7 @@
\e escape (hex 1B)
\f form feed (hex 0C)
\n linefeed (hex 0A)
- \r carriage return (hex 0D)
+ \r carriage return (hex 0D) (but see below)
\t tab (hex 09)
\0dd character with octal code 0dd
\ddd character with octal code ddd, or backreference
@@ -6257,53 +6266,58 @@
\N{U+hhh..} character with Unicode hex code point hhh..
\uhhhh character with hex code hhhh (when PCRE2_ALT_BSUX is set)
- The \N{U+hhh..} escape sequence is recognized only when the PCRE2_UTF
+ There are some legacy applications where the escape sequence \r is
+ expected to match a newline. If the PCRE2_EXTRA_ESCAPED_CR_IS_LF option
+ is set, \r in a pattern is converted to \n so that it matches a LF
+ (linefeed) instead of a CR (carriage return) character.
+
+ The \N{U+hhh..} escape sequence is recognized only when the PCRE2_UTF
option is set, that is, when PCRE2 is operating in a Unicode mode. Perl
- also uses \N{name} to specify characters by Unicode name; PCRE2 does
- not support this. Note that when \N is not followed by an opening
- brace (curly bracket) it has an entirely different meaning, matching
+ also uses \N{name} to specify characters by Unicode name; PCRE2 does
+ not support this. Note that when \N is not followed by an opening
+ brace (curly bracket) it has an entirely different meaning, matching
any character that is not a newline.
- The precise effect of \cx on ASCII characters is as follows: if x is a
- lower case letter, it is converted to upper case. Then bit 6 of the
+ The precise effect of \cx on ASCII characters is as follows: if x is a
+ lower case letter, it is converted to upper case. Then bit 6 of the
character (hex 40) is inverted. Thus \cA to \cZ become hex 01 to hex 1A
- (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and \c; becomes
- hex 7B (; is 3B). If the code unit following \c has a value less than
+ (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and \c; becomes
+ hex 7B (; is 3B). If the code unit following \c has a value less than
32 or greater than 126, a compile-time error occurs.
- When PCRE2 is compiled in EBCDIC mode, \N{U+hhh..} is not supported.
+ When PCRE2 is compiled in EBCDIC mode, \N{U+hhh..} is not supported.
\a, \e, \f, \n, \r, and \t generate the appropriate EBCDIC code values.
The \c escape is processed as specified for Perl in the perlebcdic doc-
- ument. The only characters that are allowed after \c are A-Z, a-z, or
- one of @, [, \, ], ^, _, or ?. Any other character provokes a compile-
- time error. The sequence \c@ encodes character code 0; after \c the
- letters (in either case) encode characters 1-26 (hex 01 to hex 1A); [,
- \, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and \c?
+ ument. The only characters that are allowed after \c are A-Z, a-z, or
+ one of @, [, \, ], ^, _, or ?. Any other character provokes a compile-
+ time error. The sequence \c@ encodes character code 0; after \c the
+ letters (in either case) encode characters 1-26 (hex 01 to hex 1A); [,
+ \, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and \c?
becomes either 255 (hex FF) or 95 (hex 5F).
- Thus, apart from \c?, these escapes generate the same character code
- values as they do in an ASCII environment, though the meanings of the
- values mostly differ. For example, \cG always generates code value 7,
+ Thus, apart from \c?, these escapes generate the same character code
+ values as they do in an ASCII environment, though the meanings of the
+ values mostly differ. For example, \cG always generates code value 7,
which is BEL in ASCII but DEL in EBCDIC.
- The sequence \c? generates DEL (127, hex 7F) in an ASCII environment,
- but because 127 is not a control character in EBCDIC, Perl makes it
- generate the APC character. Unfortunately, there are several variants
- of EBCDIC. In most of them the APC character has the value 255 (hex
- FF), but in the one Perl calls POSIX-BC its value is 95 (hex 5F). If
+ The sequence \c? generates DEL (127, hex 7F) in an ASCII environment,
+ but because 127 is not a control character in EBCDIC, Perl makes it
+ generate the APC character. Unfortunately, there are several variants
+ of EBCDIC. In most of them the APC character has the value 255 (hex
+ FF), but in the one Perl calls POSIX-BC its value is 95 (hex 5F). If
certain other characters have POSIX-BC values, PCRE2 makes \c? generate
95; otherwise it generates 255.
- After \0 up to two further octal digits are read. If there are fewer
- than two digits, just those that are present are used. Thus the
+ After \0 up to two further octal digits are read. If there are fewer
+ than two digits, just those that are present are used. Thus the
sequence \0\x\015 specifies two binary zeros followed by a CR character
(code value 13). Make sure you supply two digits after the initial zero
if the pattern character that follows is itself an octal digit.
- The escape \o must be followed by a sequence of octal digits, enclosed
- in braces. An error occurs if this is not the case. This escape is a
- recent addition to Perl; it provides way of specifying character code
- points as octal numbers greater than 0777, and it also allows octal
+ The escape \o must be followed by a sequence of octal digits, enclosed
+ in braces. An error occurs if this is not the case. This escape is a
+ recent addition to Perl; it provides way of specifying character code
+ points as octal numbers greater than 0777, and it also allows octal
numbers and backreferences to be unambiguously specified.
For greater clarity and unambiguity, it is best to avoid following \ by
@@ -6316,16 +6330,16 @@
Outside a character class, PCRE2 reads the digit and any following dig-
its as a decimal number. If the number is less than 10, begins with the
- digit 8 or 9, or if there are at least that many previous capturing
- left parentheses in the expression, the entire sequence is taken as a
- backreference. A description of how this works is given later, follow-
- ing the discussion of parenthesized subpatterns. Otherwise, up to
+ digit 8 or 9, or if there are at least that many previous capturing
+ left parentheses in the expression, the entire sequence is taken as a
+ backreference. A description of how this works is given later, follow-
+ ing the discussion of parenthesized subpatterns. Otherwise, up to
three octal digits are read to form a character code.
- Inside a character class, PCRE2 handles \8 and \9 as the literal char-
- acters "8" and "9", and otherwise reads up to three octal digits fol-
+ Inside a character class, PCRE2 handles \8 and \9 as the literal char-
+ acters "8" and "9", and otherwise reads up to three octal digits fol-
lowing the backslash, using them to generate a data character. Any sub-
- sequent digits stand for themselves. For example, outside a character
+ sequent digits stand for themselves. For example, outside a character
class:
\040 is another way of writing an ASCII space
@@ -6342,31 +6356,31 @@
the value 255 (decimal)
\81 is always a backreference
- Note that octal values of 100 or greater that are specified using this
- syntax must not be introduced by a leading zero, because no more than
+ Note that octal values of 100 or greater that are specified using this
+ syntax must not be introduced by a leading zero, because no more than
three octal digits are ever read.
- By default, after \x that is not followed by {, from zero to two hexa-
- decimal digits are read (letters can be in upper or lower case). Any
+ By default, after \x that is not followed by {, from zero to two hexa-
+ decimal digits are read (letters can be in upper or lower case). Any
number of hexadecimal digits may appear between \x{ and }. If a charac-
- ter other than a hexadecimal digit appears between \x{ and }, or if
+ ter other than a hexadecimal digit appears between \x{ and }, or if
there is no terminating }, an error occurs.
- If the PCRE2_ALT_BSUX option is set, the interpretation of \x is as
+ If the PCRE2_ALT_BSUX option is set, the interpretation of \x is as
just described only when it is followed by two hexadecimal digits. Oth-
- erwise, it matches a literal "x" character. In this mode, support for
- code points greater than 256 is provided by \u, which must be followed
- by four hexadecimal digits; otherwise it matches a literal "u" charac-
+ erwise, it matches a literal "x" character. In this mode, support for
+ code points greater than 256 is provided by \u, which must be followed
+ by four hexadecimal digits; otherwise it matches a literal "u" charac-
ter.
Characters whose value is less than 256 can be defined by either of the
two syntaxes for \x (or by \u in PCRE2_ALT_BSUX mode). There is no dif-
- ference in the way they are handled. For example, \xdc is exactly the
+ ference in the way they are handled. For example, \xdc is exactly the
same as \x{dc} (or \u00dc in PCRE2_ALT_BSUX mode).
Constraints on character values
- Characters that are specified using octal or hexadecimal numbers are
+ Characters that are specified using octal or hexadecimal numbers are
limited to certain values, as follows:
8-bit non-UTF mode no greater than 0xff
@@ -6375,27 +6389,27 @@
All UTF modes no greater than 0x10ffff and a valid code point
Invalid Unicode code points are all those in the range 0xd800 to 0xdfff
- (the so-called "surrogate" code points). The check for these can be
- disabled by the caller of pcre2_compile() by setting the option
- PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES. However, this is possible only in
- UTF-8 and UTF-32 modes, because these values are not representable in
+ (the so-called "surrogate" code points). The check for these can be
+ disabled by the caller of pcre2_compile() by setting the option
+ PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES. However, this is possible only in
+ UTF-8 and UTF-32 modes, because these values are not representable in
UTF-16.
Escape sequences in character classes
All the sequences that define a single character value can be used both
- inside and outside character classes. In addition, inside a character
+ inside and outside character classes. In addition, inside a character
class, \b is interpreted as the backspace character (hex 08).
When not followed by an opening brace, \N is not allowed in a character
- class. \B, \R, and \X are not special inside a character class. Like
- other unrecognized alphabetic escape sequences, they cause an error.
+ class. \B, \R, and \X are not special inside a character class. Like
+ other unrecognized alphabetic escape sequences, they cause an error.
Outside a character class, these sequences have different meanings.
Unsupported escape sequences
- In Perl, the sequences \F, \l, \L, \u, and \U are recognized by its
- string handler and used to modify the case of following characters. By
+ In Perl, the sequences \F, \l, \L, \u, and \U are recognized by its
+ string handler and used to modify the case of following characters. By
default, PCRE2 does not support these escape sequences. However, if the
PCRE2_ALT_BSUX option is set, \U matches a "U" character, and \u can be
used to define a character by code point, as described above.
@@ -6402,17 +6416,17 @@
Absolute and relative backreferences
- The sequence \g followed by a signed or unsigned number, optionally
- enclosed in braces, is an absolute or relative backreference. A named
- backreference can be coded as \g{name}. Backreferences are discussed
+ The sequence \g followed by a signed or unsigned number, optionally
+ enclosed in braces, is an absolute or relative backreference. A named
+ backreference can be coded as \g{name}. Backreferences are discussed
later, following the discussion of parenthesized subpatterns.
Absolute and relative subroutine calls
- For compatibility with Oniguruma, the non-Perl syntax \g followed by a
+ For compatibility with Oniguruma, the non-Perl syntax \g followed by a
name or a number enclosed either in angle brackets or single quotes, is
- an alternative syntax for referencing a subpattern as a "subroutine".
- Details are discussed later. Note that \g{...} (Perl syntax) and
+ an alternative syntax for referencing a subpattern as a "subroutine".
+ Details are discussed later. Note that \g{...} (Perl syntax) and
\g<...> (Oniguruma syntax) are not synonymous. The former is a backref-
erence; the latter is a subroutine call.
@@ -6432,43 +6446,43 @@
\w any "word" character
\W any "non-word" character
- The \N escape sequence has the same meaning as the "." metacharacter
- when PCRE2_DOTALL is not set, but setting PCRE2_DOTALL does not change
+ The \N escape sequence has the same meaning as the "." metacharacter
+ when PCRE2_DOTALL is not set, but setting PCRE2_DOTALL does not change
the meaning of \N. Note that when \N is followed by an opening brace it
has a different meaning. See the section entitled "Non-printing charac-
- ters" above for details. Perl also uses \N{name} to specify characters
+ ters" above for details. Perl also uses \N{name} to specify characters
by Unicode name; PCRE2 does not support this.
- Each pair of lower and upper case escape sequences partitions the com-
- plete set of characters into two disjoint sets. Any given character
- matches one, and only one, of each pair. The sequences can appear both
- inside and outside character classes. They each match one character of
- the appropriate type. If the current matching point is at the end of
- the subject string, all of them fail, because there is no character to
+ Each pair of lower and upper case escape sequences partitions the com-
+ plete set of characters into two disjoint sets. Any given character
+ matches one, and only one, of each pair. The sequences can appear both
+ inside and outside character classes. They each match one character of
+ the appropriate type. If the current matching point is at the end of
+ the subject string, all of them fail, because there is no character to
match.
- The default \s characters are HT (9), LF (10), VT (11), FF (12), CR
- (13), and space (32), which are defined as white space in the "C"
+ The default \s characters are HT (9), LF (10), VT (11), FF (12), CR
+ (13), and space (32), which are defined as white space in the "C"
locale. This list may vary if locale-specific matching is taking place.
- For example, in some locales the "non-breaking space" character (\xA0)
+ For example, in some locales the "non-breaking space" character (\xA0)
is recognized as white space, and in others the VT character is not.
- A "word" character is an underscore or any character that is a letter
- or digit. By default, the definition of letters and digits is con-
+ A "word" character is an underscore or any character that is a letter
+ or digit. By default, the definition of letters and digits is con-
trolled by PCRE2's low-valued character tables, and may vary if locale-
specific matching is taking place (see "Locale support" in the pcre2api
- page). For example, in a French locale such as "fr_FR" in Unix-like
- systems, or "french" in Windows, some character codes greater than 127
- are used for accented letters, and these are then matched by \w. The
+ page). For example, in a French locale such as "fr_FR" in Unix-like
+ systems, or "french" in Windows, some character codes greater than 127
+ are used for accented letters, and these are then matched by \w. The
use of locales with Unicode is discouraged.
- By default, characters whose code points are greater than 127 never
+ By default, characters whose code points are greater than 127 never
match \d, \s, or \w, and always match \D, \S, and \W, although this may
- be different for characters in the range 128-255 when locale-specific
- matching is happening. These escape sequences retain their original
- meanings from before Unicode support was available, mainly for effi-
- ciency reasons. If the PCRE2_UCP option is set, the behaviour is
- changed so that Unicode properties are used to determine character
+ be different for characters in the range 128-255 when locale-specific
+ matching is happening. These escape sequences retain their original
+ meanings from before Unicode support was available, mainly for effi-
+ ciency reasons. If the PCRE2_UCP option is set, the behaviour is
+ changed so that Unicode properties are used to determine character
types, as follows:
\d any character that matches \p{Nd} (decimal digit)
@@ -6475,15 +6489,15 @@
\s any character that matches \p{Z} or \h or \v
\w any character that matches \p{L} or \p{N}, plus underscore
- The upper case escapes match the inverse sets of characters. Note that
- \d matches only decimal digits, whereas \w matches any Unicode digit,
+ The upper case escapes match the inverse sets of characters. Note that
+ \d matches only decimal digits, whereas \w matches any Unicode digit,
as well as any Unicode letter, and underscore. Note also that PCRE2_UCP
- affects \b, and \B because they are defined in terms of \w and \W.
+ affects \b, and \B because they are defined in terms of \w and \W.
Matching these sequences is noticeably slower when PCRE2_UCP is set.
- The sequences \h, \H, \v, and \V, in contrast to the other sequences,
- which match only ASCII characters by default, always match a specific
- list of code points, whether or not PCRE2_UCP is set. The horizontal
+ The sequences \h, \H, \v, and \V, in contrast to the other sequences,
+ which match only ASCII characters by default, always match a specific
+ list of code points, whether or not PCRE2_UCP is set. The horizontal
space characters are:
U+0009 Horizontal tab (HT)
@@ -6516,36 +6530,36 @@
U+2028 Line separator
U+2029 Paragraph separator
- In 8-bit, non-UTF-8 mode, only the characters with code points less
+ In 8-bit, non-UTF-8 mode, only the characters with code points less
than 256 are relevant.
Newline sequences
- Outside a character class, by default, the escape sequence \R matches
- any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent
+ Outside a character class, by default, the escape sequence \R matches
+ any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent
to the following:
(?>\r\n|\n|\x0b|\f|\r|\x85)
- This is an example of an "atomic group", details of which are given
+ This is an example of an "atomic group", details of which are given
below. This particular group matches either the two-character sequence
- CR followed by LF, or one of the single characters LF (linefeed,
- U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car-
- riage return, U+000D), or NEL (next line, U+0085). Because this is an
- atomic group, the two-character sequence is treated as a single unit
+ CR followed by LF, or one of the single characters LF (linefeed,
+ U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car-
+ riage return, U+000D), or NEL (next line, U+0085). Because this is an
+ atomic group, the two-character sequence is treated as a single unit
that cannot be split.
In other modes, two additional characters whose code points are greater
than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
- rator, U+2029). Unicode support is not needed for these characters to
+ rator, U+2029). Unicode support is not needed for these characters to
be recognized.
It is possible to restrict \R to match only CR, LF, or CRLF (instead of
- the complete set of Unicode line endings) by setting the option
- PCRE2_BSR_ANYCRLF at compile time. (BSR is an abbrevation for "back-
+ the complete set of Unicode line endings) by setting the option
+ PCRE2_BSR_ANYCRLF at compile time. (BSR is an abbrevation for "back-
slash R".) This can be made the default when PCRE2 is built; if this is
- the case, the other behaviour can be requested via the PCRE2_BSR_UNI-
- CODE option. It is also possible to specify these settings by starting
+ the case, the other behaviour can be requested via the PCRE2_BSR_UNI-
+ CODE option. It is also possible to specify these settings by starting
a pattern string with one of the following sequences:
(*BSR_ANYCRLF) CR, LF, or CRLF only
@@ -6553,26 +6567,26 @@
These override the default and the options given to the compiling func-
tion. Note that these special settings, which are not Perl-compatible,
- are recognized only at the very start of a pattern, and that they must
- be in upper case. If more than one of them is present, the last one is
- used. They can be combined with a change of newline convention; for
+ are recognized only at the very start of a pattern, and that they must
+ be in upper case. If more than one of them is present, the last one is
+ used. They can be combined with a change of newline convention; for
example, a pattern can start with:
(*ANY)(*BSR_ANYCRLF)
- They can also be combined with the (*UTF) or (*UCP) special sequences.
- Inside a character class, \R is treated as an unrecognized escape
+ They can also be combined with the (*UTF) or (*UCP) special sequences.
+ Inside a character class, \R is treated as an unrecognized escape
sequence, and causes an error.
Unicode character properties
- When PCRE2 is built with Unicode support (the default), three addi-
- tional escape sequences that match characters with specific properties
- are available. In 8-bit non-UTF-8 mode, these sequences are of course
- limited to testing characters whose code points are less than 256, but
+ When PCRE2 is built with Unicode support (the default), three addi-
+ tional escape sequences that match characters with specific properties
+ are available. In 8-bit non-UTF-8 mode, these sequences are of course
+ limited to testing characters whose code points are less than 256, but
they do work in this mode. In 32-bit non-UTF mode, code points greater
- than 0x10ffff (the Unicode limit) may be encountered. These are all
- treated as being in the Common script and with an unassigned type. The
+ than 0x10ffff (the Unicode limit) may be encountered. These are all
+ treated as being in the Common script and with an unassigned type. The
extra escape sequences are:
\p{xx} a character with the xx property
@@ -6579,56 +6593,56 @@
\P{xx} a character without the xx property
\X a Unicode extended grapheme cluster
- The property names represented by xx above are limited to the Unicode
+ The property names represented by xx above are limited to the Unicode
script names, the general category properties, "Any", which matches any
character (including newline), and some special PCRE2 properties
- (described in the next section). Other Perl properties such as "InMu-
- sicalSymbols" are not supported by PCRE2. Note that \P{Any} does not
+ (described in the next section). Other Perl properties such as "InMu-
+ sicalSymbols" are not supported by PCRE2. Note that \P{Any} does not
match any characters, so always causes a match failure.
Sets of Unicode characters are defined as belonging to certain scripts.
- A character from one of these sets can be matched using a script name.
+ A character from one of these sets can be matched using a script name.
For example:
\p{Greek}
\P{Han}
- Those that are not part of an identified script are lumped together as
+ Those that are not part of an identified script are lumped together as
"Common". The current list of scripts is:
- Adlam, Ahom, Anatolian_Hieroglyphs, Arabic, Armenian, Avestan, Bali-
- nese, Bamum, Bassa_Vah, Batak, Bengali, Bhaiksuki, Bopomofo, Brahmi,
- Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Caucasian_Alba-
- nian, Chakma, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot,
- Cyrillic, Deseret, Devanagari, Dogra, Duployan, Egyptian_Hieroglyphs,
- Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, Greek,
- Gujarati, Gunjala_Gondi, Gurmukhi, Han, Hangul, Hanifi_Rohingya,
- Hanunoo, Hatran, Hebrew, Hiragana, Imperial_Aramaic, Inherited,
- Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kan-
- nada, Katakana, Kayah_Li, Kharoshthi, Khmer, Khojki, Khudawadi, Lao,
- Latin, Lepcha, Limbu, Linear_A, Linear_B, Lisu, Lycian, Lydian, Maha-
- jani, Makasar, Malayalam, Mandaic, Manichaean, Marchen, Masaram_Gondi,
+ Adlam, Ahom, Anatolian_Hieroglyphs, Arabic, Armenian, Avestan, Bali-
+ nese, Bamum, Bassa_Vah, Batak, Bengali, Bhaiksuki, Bopomofo, Brahmi,
+ Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Caucasian_Alba-
+ nian, Chakma, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot,
+ Cyrillic, Deseret, Devanagari, Dogra, Duployan, Egyptian_Hieroglyphs,
+ Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, Greek,
+ Gujarati, Gunjala_Gondi, Gurmukhi, Han, Hangul, Hanifi_Rohingya,
+ Hanunoo, Hatran, Hebrew, Hiragana, Imperial_Aramaic, Inherited,
+ Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kan-
+ nada, Katakana, Kayah_Li, Kharoshthi, Khmer, Khojki, Khudawadi, Lao,
+ Latin, Lepcha, Limbu, Linear_A, Linear_B, Lisu, Lycian, Lydian, Maha-
+ jani, Makasar, Malayalam, Mandaic, Manichaean, Marchen, Masaram_Gondi,
Medefaidrin, Meetei_Mayek, Mende_Kikakui, Meroitic_Cursive,
- Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Multani, Myanmar,
- Nabataean, New_Tai_Lue, Newa, Nko, Nushu, Ogham, Ol_Chiki, Old_Hungar-
- ian, Old_Italic, Old_North_Arabian, Old_Permic, Old_Persian, Old_Sog-
- dian, Old_South_Arabian, Old_Turkic, Oriya, Osage, Osmanya,
+ Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Multani, Myanmar,
+ Nabataean, New_Tai_Lue, Newa, Nko, Nushu, Ogham, Ol_Chiki, Old_Hungar-
+ ian, Old_Italic, Old_North_Arabian, Old_Permic, Old_Persian, Old_Sog-
+ dian, Old_South_Arabian, Old_Turkic, Oriya, Osage, Osmanya,
Pahawh_Hmong, Palmyrene, Pau_Cin_Hau, Phags_Pa, Phoenician,
- Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha-
- vian, Siddham, SignWriting, Sinhala, Sogdian, Sora_Sompeng, Soyombo,
- Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham,
- Tai_Viet, Takri, Tamil, Tangut, Telugu, Thaana, Thai, Tibetan, Tifi-
+ Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha-
+ vian, Siddham, SignWriting, Sinhala, Sogdian, Sora_Sompeng, Soyombo,
+ Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham,
+ Tai_Viet, Takri, Tamil, Tangut, Telugu, Thaana, Thai, Tibetan, Tifi-
nagh, Tirhuta, Ugaritic, Vai, Warang_Citi, Yi, Zanabazar_Square.
Each character has exactly one Unicode general category property, spec-
- ified by a two-letter abbreviation. For compatibility with Perl, nega-
- tion can be specified by including a circumflex between the opening
- brace and the property name. For example, \p{^Lu} is the same as
+ ified by a two-letter abbreviation. For compatibility with Perl, nega-
+ tion can be specified by including a circumflex between the opening
+ brace and the property name. For example, \p{^Lu} is the same as
\P{Lu}.
If only one letter is specified with \p or \P, it includes all the gen-
- eral category properties that start with that letter. In this case, in
- the absence of negation, the curly brackets in the escape sequence are
+ eral category properties that start with that letter. In this case, in
+ the absence of negation, the curly brackets in the escape sequence are
optional; these two examples have the same effect:
\p{L}
@@ -6680,18 +6694,18 @@
Zp Paragraph separator
Zs Space separator
- The special property L& is also supported: it matches a character that
- has the Lu, Ll, or Lt property, in other words, a letter that is not
+ The special property L& is also supported: it matches a character that
+ has the Lu, Ll, or Lt property, in other words, a letter that is not
classified as a modifier or "other".
- The Cs (Surrogate) property applies only to characters in the range
- U+D800 to U+DFFF. Such characters are not valid in Unicode strings and
- so cannot be tested by PCRE2, unless UTF validity checking has been
- turned off (see the discussion of PCRE2_NO_UTF_CHECK in the pcre2api
+ The Cs (Surrogate) property applies only to characters in the range
+ U+D800 to U+DFFF. Such characters are not valid in Unicode strings and
+ so cannot be tested by PCRE2, unless UTF validity checking has been
+ turned off (see the discussion of PCRE2_NO_UTF_CHECK in the pcre2api
page). Perl does not support the Cs property.
- The long synonyms for property names that Perl supports (such as
- \p{Letter}) are not supported by PCRE2, nor is it permitted to prefix
+ The long synonyms for property names that Perl supports (such as
+ \p{Letter}) are not supported by PCRE2, nor is it permitted to prefix
any of these properties with "Is".
No character that is in the Unicode table has the Cn (unassigned) prop-
@@ -6698,47 +6712,47 @@
erty. Instead, this property is assumed for any code point that is not
in the Unicode table.
- Specifying caseless matching does not affect these escape sequences.
- For example, \p{Lu} always matches only upper case letters. This is
+ Specifying caseless matching does not affect these escape sequences.
+ For example, \p{Lu} always matches only upper case letters. This is
different from the behaviour of current versions of Perl.
- Matching characters by Unicode property is not fast, because PCRE2 has
- to do a multistage table lookup in order to find a character's prop-
+ Matching characters by Unicode property is not fast, because PCRE2 has
+ to do a multistage table lookup in order to find a character's prop-
erty. That is why the traditional escape sequences such as \d and \w do
- not use Unicode properties in PCRE2 by default, though you can make
- them do so by setting the PCRE2_UCP option or by starting the pattern
+ not use Unicode properties in PCRE2 by default, though you can make
+ them do so by setting the PCRE2_UCP option or by starting the pattern
with (*UCP).
Extended grapheme clusters
- The \X escape matches any number of Unicode characters that form an
+ The \X escape matches any number of Unicode characters that form an
"extended grapheme cluster", and treats the sequence as an atomic group
- (see below). Unicode supports various kinds of composite character by
- giving each character a grapheme breaking property, and having rules
+ (see below). Unicode supports various kinds of composite character by
+ giving each character a grapheme breaking property, and having rules
that use these properties to define the boundaries of extended grapheme
- clusters. The rules are defined in Unicode Standard Annex 29, "Unicode
- Text Segmentation". Unicode 11.0.0 abandoned the use of some previous
- properties that had been used for emojis. Instead it introduced vari-
- ous emoji-specific properties. PCRE2 uses only the Extended Picto-
+ clusters. The rules are defined in Unicode Standard Annex 29, "Unicode
+ Text Segmentation". Unicode 11.0.0 abandoned the use of some previous
+ properties that had been used for emojis. Instead it introduced vari-
+ ous emoji-specific properties. PCRE2 uses only the Extended Picto-
graphic property.
- \X always matches at least one character. Then it decides whether to
+ \X always matches at least one character. Then it decides whether to
add additional characters according to the following rules for ending a
cluster:
1. End at the end of the subject string.
- 2. Do not end between CR and LF; otherwise end after any control char-
+ 2. Do not end between CR and LF; otherwise end after any control char-
acter.
- 3. Do not break Hangul (a Korean script) syllable sequences. Hangul
- characters are of five types: L, V, T, LV, and LVT. An L character may
- be followed by an L, V, LV, or LVT character; an LV or V character may
+ 3. Do not break Hangul (a Korean script) syllable sequences. Hangul
+ characters are of five types: L, V, T, LV, and LVT. An L character may
+ be followed by an L, V, LV, or LVT character; an LV or V character may
be followed by a V or T character; an LVT or T character may be follwed
only by a T character.
- 4. Do not end before extending characters or spacing marks or the
- "zero-width joiner" character. Characters with the "mark" property
+ 4. Do not end before extending characters or spacing marks or the
+ "zero-width joiner" character. Characters with the "mark" property
always have the "extend" grapheme breaking property.
5. Do not end after prepend characters.
@@ -6745,11 +6759,11 @@
6. Do not break within emoji modifier sequences or emoji zwj sequences.
That is, do not break between characters with the Extended_Pictographic
- property. Extend and ZWJ characters are allowed between the charac-
+ property. Extend and ZWJ characters are allowed between the charac-
ters.
- 7. Do not break within emoji flag sequences. That is, do not break
- between regional indicator (RI) characters if there are an odd number
+ 7. Do not break within emoji flag sequences. That is, do not break
+ between regional indicator (RI) characters if there are an odd number
of RI characters before the break point.
8. Otherwise, end the cluster.
@@ -6756,10 +6770,10 @@
PCRE2's additional properties
- As well as the standard Unicode properties described above, PCRE2 sup-
- ports four more that make it possible to convert traditional escape
+ As well as the standard Unicode properties described above, PCRE2 sup-
+ ports four more that make it possible to convert traditional escape
sequences such as \w and \s to use Unicode properties. PCRE2 uses these
- non-standard, non-Perl properties internally when PCRE2_UCP is set.
+ non-standard, non-Perl properties internally when PCRE2_UCP is set.
However, they may also be used explicitly. These properties are:
Xan Any alphanumeric character
@@ -6767,42 +6781,42 @@
Xsp Any Perl space character
Xwd Any Perl "word" character
- Xan matches characters that have either the L (letter) or the N (num-
- ber) property. Xps matches the characters tab, linefeed, vertical tab,
- form feed, or carriage return, and any other character that has the Z
- (separator) property. Xsp is the same as Xps; in PCRE1 it used to
- exclude vertical tab, for Perl compatibility, but Perl changed. Xwd
+ Xan matches characters that have either the L (letter) or the N (num-
+ ber) property. Xps matches the characters tab, linefeed, vertical tab,
+ form feed, or carriage return, and any other character that has the Z
+ (separator) property. Xsp is the same as Xps; in PCRE1 it used to
+ exclude vertical tab, for Perl compatibility, but Perl changed. Xwd
matches the same characters as Xan, plus underscore.
- There is another non-standard property, Xuc, which matches any charac-
- ter that can be represented by a Universal Character Name in C++ and
- other programming languages. These are the characters $, @, ` (grave
- accent), and all characters with Unicode code points greater than or
- equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that
- most base (ASCII) characters are excluded. (Universal Character Names
- are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit.
+ There is another non-standard property, Xuc, which matches any charac-
+ ter that can be represented by a Universal Character Name in C++ and
+ other programming languages. These are the characters $, @, ` (grave
+ accent), and all characters with Unicode code points greater than or
+ equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that
+ most base (ASCII) characters are excluded. (Universal Character Names
+ are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit.
Note that the Xuc property does not match these sequences but the char-
acters that they represent.)
Resetting the match start
- In normal use, the escape sequence \K causes any previously matched
- characters not to be included in the final matched sequence that is
+ In normal use, the escape sequence \K causes any previously matched
+ characters not to be included in the final matched sequence that is
returned. For example, the pattern:
foo\Kbar
- matches "foobar", but reports that it has matched "bar". \K does not
+ matches "foobar", but reports that it has matched "bar". \K does not
interact with anchoring in any way. The pattern:
^foo\Kbar
- matches only when the subject begins with "foobar" (in single line
- mode), though it again reports the matched string as "bar". This fea-
- ture is similar to a lookbehind assertion (described below). However,
- in this case, the part of the subject before the real match does not
- have to be of fixed length, as lookbehind assertions do. The use of \K
- does not interfere with the setting of captured substrings. For exam-
+ matches only when the subject begins with "foobar" (in single line
+ mode), though it again reports the matched string as "bar". This fea-
+ ture is similar to a lookbehind assertion (described below). However,
+ in this case, the part of the subject before the real match does not
+ have to be of fixed length, as lookbehind assertions do. The use of \K
+ does not interfere with the setting of captured substrings. For exam-
ple, when the pattern
(foo)\Kbar
@@ -6809,27 +6823,27 @@
matches "foobar", the first substring is still set to "foo".
- Perl documents that the use of \K within assertions is "not well
- defined". In PCRE2, \K is acted upon when it occurs inside positive
- assertions, but is ignored in negative assertions. Note that when a
- pattern such as (?=ab\K) matches, the reported start of the match can
- be greater than the end of the match. Using \K in a lookbehind asser-
- tion at the start of a pattern can also lead to odd effects. For exam-
+ Perl documents that the use of \K within assertions is "not well
+ defined". In PCRE2, \K is acted upon when it occurs inside positive
+ assertions, but is ignored in negative assertions. Note that when a
+ pattern such as (?=ab\K) matches, the reported start of the match can
+ be greater than the end of the match. Using \K in a lookbehind asser-
+ tion at the start of a pattern can also lead to odd effects. For exam-
ple, consider this pattern:
(?<=\Kfoo)bar
- If the subject is "foobar", a call to pcre2_match() with a starting
- offset of 3 succeeds and reports the matching string as "foobar", that
- is, the start of the reported match is earlier than where the match
+ If the subject is "foobar", a call to pcre2_match() with a starting
+ offset of 3 succeeds and reports the matching string as "foobar", that
+ is, the start of the reported match is earlier than where the match
started.
Simple assertions
- The final use of backslash is for certain simple assertions. An asser-
- tion specifies a condition that has to be met at a particular point in
- a match, without consuming any characters from the subject string. The
- use of subpatterns for more complicated assertions is described below.
+ The final use of backslash is for certain simple assertions. An asser-
+ tion specifies a condition that has to be met at a particular point in
+ a match, without consuming any characters from the subject string. The
+ use of subpatterns for more complicated assertions is described below.
The backslashed assertions are:
\b matches at a word boundary
@@ -6840,47 +6854,47 @@
\z matches only at the end of the subject
\G matches at the first matching position in the subject
- Inside a character class, \b has a different meaning; it matches the
- backspace character. If any other of these assertions appears in a
+ Inside a character class, \b has a different meaning; it matches the
+ backspace character. If any other of these assertions appears in a
character class, an "invalid escape sequence" error is generated.
- A word boundary is a position in the subject string where the current
- character and the previous character do not both match \w or \W (i.e.
- one matches \w and the other matches \W), or the start or end of the
- string if the first or last character matches \w, respectively. In a
- UTF mode, the meanings of \w and \W can be changed by setting the
+ A word boundary is a position in the subject string where the current
+ character and the previous character do not both match \w or \W (i.e.
+ one matches \w and the other matches \W), or the start or end of the
+ string if the first or last character matches \w, respectively. In a
+ UTF mode, the meanings of \w and \W can be changed by setting the
PCRE2_UCP option. When this is done, it also affects \b and \B. Neither
- PCRE2 nor Perl has a separate "start of word" or "end of word" metase-
- quence. However, whatever follows \b normally determines which it is.
+ PCRE2 nor Perl has a separate "start of word" or "end of word" metase-
+ quence. However, whatever follows \b normally determines which it is.
For example, the fragment \ba matches "a" at the start of a word.
- The \A, \Z, and \z assertions differ from the traditional circumflex
+ The \A, \Z, and \z assertions differ from the traditional circumflex
and dollar (described in the next section) in that they only ever match
- at the very start and end of the subject string, whatever options are
- set. Thus, they are independent of multiline mode. These three asser-
- tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options,
- which affect only the behaviour of the circumflex and dollar metachar-
- acters. However, if the startoffset argument of pcre2_match() is non-
- zero, indicating that matching is to start at a point other than the
- beginning of the subject, \A can never match. The difference between
- \Z and \z is that \Z matches before a newline at the end of the string
+ at the very start and end of the subject string, whatever options are
+ set. Thus, they are independent of multiline mode. These three asser-
+ tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options,
+ which affect only the behaviour of the circumflex and dollar metachar-
+ acters. However, if the startoffset argument of pcre2_match() is non-
+ zero, indicating that matching is to start at a point other than the
+ beginning of the subject, \A can never match. The difference between
+ \Z and \z is that \Z matches before a newline at the end of the string
as well as at the very end, whereas \z matches only at the end.
- The \G assertion is true only when the current matching position is at
- the start point of the matching process, as specified by the startoff-
- set argument of pcre2_match(). It differs from \A when the value of
- startoffset is non-zero. By calling pcre2_match() multiple times with
- appropriate arguments, you can mimic Perl's /g option, and it is in
+ The \G assertion is true only when the current matching position is at
+ the start point of the matching process, as specified by the startoff-
+ set argument of pcre2_match(). It differs from \A when the value of
+ startoffset is non-zero. By calling pcre2_match() multiple times with
+ appropriate arguments, you can mimic Perl's /g option, and it is in
this kind of implementation where \G can be useful.
- Note, however, that PCRE2's implementation of \G, being true at the
- starting character of the matching process, is subtly different from
- Perl's, which defines it as true at the end of the previous match. In
- Perl, these can be different when the previously matched string was
+ Note, however, that PCRE2's implementation of \G, being true at the
+ starting character of the matching process, is subtly different from
+ Perl's, which defines it as true at the end of the previous match. In
+ Perl, these can be different when the previously matched string was
empty. Because PCRE2 does just one match at a time, it cannot reproduce
this behaviour.
- If all the alternatives of a pattern begin with \G, the expression is
+ If all the alternatives of a pattern begin with \G, the expression is
anchored to the starting match position, and the "anchored" flag is set
in the compiled regular expression.
@@ -6887,70 +6901,70 @@
CIRCUMFLEX AND DOLLAR
- The circumflex and dollar metacharacters are zero-width assertions.
- That is, they test for a particular condition being true without con-
+ The circumflex and dollar metacharacters are zero-width assertions.
+ That is, they test for a particular condition being true without con-
suming any characters from the subject string. These two metacharacters
- are concerned with matching the starts and ends of lines. If the new-
- line convention is set so that only the two-character sequence CRLF is
- recognized as a newline, isolated CR and LF characters are treated as
+ are concerned with matching the starts and ends of lines. If the new-
+ line convention is set so that only the two-character sequence CRLF is
+ recognized as a newline, isolated CR and LF characters are treated as
ordinary data characters, and are not recognized as newlines.
Outside a character class, in the default matching mode, the circumflex
- character is an assertion that is true only if the current matching
- point is at the start of the subject string. If the startoffset argu-
- ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum-
- flex can never match if the PCRE2_MULTILINE option is unset. Inside a
- character class, circumflex has an entirely different meaning (see
+ character is an assertion that is true only if the current matching
+ point is at the start of the subject string. If the startoffset argu-
+ ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum-
+ flex can never match if the PCRE2_MULTILINE option is unset. Inside a
+ character class, circumflex has an entirely different meaning (see
below).
- Circumflex need not be the first character of the pattern if a number
- of alternatives are involved, but it should be the first thing in each
- alternative in which it appears if the pattern is ever to match that
- branch. If all possible alternatives start with a circumflex, that is,
- if the pattern is constrained to match only at the start of the sub-
- ject, it is said to be an "anchored" pattern. (There are also other
+ Circumflex need not be the first character of the pattern if a number
+ of alternatives are involved, but it should be the first thing in each
+ alternative in which it appears if the pattern is ever to match that
+ branch. If all possible alternatives start with a circumflex, that is,
+ if the pattern is constrained to match only at the start of the sub-
+ ject, it is said to be an "anchored" pattern. (There are also other
constructs that can cause a pattern to be anchored.)
- The dollar character is an assertion that is true only if the current
- matching point is at the end of the subject string, or immediately
- before a newline at the end of the string (by default), unless
+ The dollar character is an assertion that is true only if the current
+ matching point is at the end of the subject string, or immediately
+ before a newline at the end of the string (by default), unless
PCRE2_NOTEOL is set. Note, however, that it does not actually match the
newline. Dollar need not be the last character of the pattern if a num-
ber of alternatives are involved, but it should be the last item in any
- branch in which it appears. Dollar has no special meaning in a charac-
+ branch in which it appears. Dollar has no special meaning in a charac-
ter class.
- The meaning of dollar can be changed so that it matches only at the
- very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at
+ The meaning of dollar can be changed so that it matches only at the
+ very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at
compile time. This does not affect the \Z assertion.
The meanings of the circumflex and dollar metacharacters are changed if
- the PCRE2_MULTILINE option is set. When this is the case, a dollar
- character matches before any newlines in the string, as well as at the
- very end, and a circumflex matches immediately after internal newlines
- as well as at the start of the subject string. It does not match after
- a newline that ends the string, for compatibility with Perl. However,
+ the PCRE2_MULTILINE option is set. When this is the case, a dollar
+ character matches before any newlines in the string, as well as at the
+ very end, and a circumflex matches immediately after internal newlines
+ as well as at the start of the subject string. It does not match after
+ a newline that ends the string, for compatibility with Perl. However,
this can be changed by setting the PCRE2_ALT_CIRCUMFLEX option.
- For example, the pattern /^abc$/ matches the subject string "def\nabc"
- (where \n represents a newline) in multiline mode, but not otherwise.
- Consequently, patterns that are anchored in single line mode because
- all branches start with ^ are not anchored in multiline mode, and a
- match for circumflex is possible when the startoffset argument of
- pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored
+ For example, the pattern /^abc$/ matches the subject string "def\nabc"
+ (where \n represents a newline) in multiline mode, but not otherwise.
+ Consequently, patterns that are anchored in single line mode because
+ all branches start with ^ are not anchored in multiline mode, and a
+ match for circumflex is possible when the startoffset argument of
+ pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored
if PCRE2_MULTILINE is set.
- When the newline convention (see "Newline conventions" below) recog-
- nizes the two-character sequence CRLF as a newline, this is preferred,
- even if the single characters CR and LF are also recognized as new-
- lines. For example, if the newline convention is "any", a multiline
- mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather
- than after CR, even though CR on its own is a valid newline. (It also
+ When the newline convention (see "Newline conventions" below) recog-
+ nizes the two-character sequence CRLF as a newline, this is preferred,
+ even if the single characters CR and LF are also recognized as new-
+ lines. For example, if the newline convention is "any", a multiline
+ mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather
+ than after CR, even though CR on its own is a valid newline. (It also
matches at the very start of the string, of course.)
- Note that the sequences \A, \Z, and \z can be used to match the start
- and end of the subject in both modes, and if all branches of a pattern
- start with \A it is always anchored, whether or not PCRE2_MULTILINE is
+ Note that the sequences \A, \Z, and \z can be used to match the start
+ and end of the subject in both modes, and if all branches of a pattern
+ start with \A it is always anchored, whether or not PCRE2_MULTILINE is
set.
@@ -6957,73 +6971,73 @@
FULL STOP (PERIOD, DOT) AND \N
Outside a character class, a dot in the pattern matches any one charac-
- ter in the subject string except (by default) a character that signi-
+ ter in the subject string except (by default) a character that signi-
fies the end of a line.
- When a line ending is defined as a single character, dot never matches
- that character; when the two-character sequence CRLF is used, dot does
- not match CR if it is immediately followed by LF, but otherwise it
- matches all characters (including isolated CRs and LFs). When any Uni-
- code line endings are being recognized, dot does not match CR or LF or
+ When a line ending is defined as a single character, dot never matches
+ that character; when the two-character sequence CRLF is used, dot does
+ not match CR if it is immediately followed by LF, but otherwise it
+ matches all characters (including isolated CRs and LFs). When any Uni-
+ code line endings are being recognized, dot does not match CR or LF or
any of the other line ending characters.
- The behaviour of dot with regard to newlines can be changed. If the
- PCRE2_DOTALL option is set, a dot matches any one character, without
- exception. If the two-character sequence CRLF is present in the sub-
+ The behaviour of dot with regard to newlines can be changed. If the
+ PCRE2_DOTALL option is set, a dot matches any one character, without
+ exception. If the two-character sequence CRLF is present in the sub-
ject string, it takes two dots to match it.
- The handling of dot is entirely independent of the handling of circum-
- flex and dollar, the only relationship being that they both involve
+ The handling of dot is entirely independent of the handling of circum-
+ flex and dollar, the only relationship being that they both involve
newlines. Dot has no special meaning in a character class.
- The escape sequence \N when not followed by an opening brace behaves
- like a dot, except that it is not affected by the PCRE2_DOTALL option.
- In other words, it matches any character except one that signifies the
+ The escape sequence \N when not followed by an opening brace behaves
+ like a dot, except that it is not affected by the PCRE2_DOTALL option.
+ In other words, it matches any character except one that signifies the
end of a line.
When \N is followed by an opening brace it has a different meaning. See
- the section entitled "Non-printing characters" above for details. Perl
- also uses \N{name} to specify characters by Unicode name; PCRE2 does
+ the section entitled "Non-printing characters" above for details. Perl
+ also uses \N{name} to specify characters by Unicode name; PCRE2 does
not support this.
MATCHING A SINGLE CODE UNIT
- Outside a character class, the escape sequence \C matches any one code
- unit, whether or not a UTF mode is set. In the 8-bit library, one code
- unit is one byte; in the 16-bit library it is a 16-bit unit; in the
- 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches
- line-ending characters. The feature is provided in Perl in order to
+ Outside a character class, the escape sequence \C matches any one code
+ unit, whether or not a UTF mode is set. In the 8-bit library, one code
+ unit is one byte; in the 16-bit library it is a 16-bit unit; in the
+ 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches
+ line-ending characters. The feature is provided in Perl in order to
match individual bytes in UTF-8 mode, but it is unclear how it can use-
fully be used.
- Because \C breaks up characters into individual code units, matching
- one unit with \C in UTF-8 or UTF-16 mode means that the rest of the
- string may start with a malformed UTF character. This has undefined
+ Because \C breaks up characters into individual code units, matching
+ one unit with \C in UTF-8 or UTF-16 mode means that the rest of the
+ string may start with a malformed UTF character. This has undefined
results, because PCRE2 assumes that it is matching character by charac-
- ter in a valid UTF string (by default it checks the subject string's
- validity at the start of processing unless the PCRE2_NO_UTF_CHECK
+ ter in a valid UTF string (by default it checks the subject string's
+ validity at the start of processing unless the PCRE2_NO_UTF_CHECK
option is used).
- An application can lock out the use of \C by setting the
- PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also
+ An application can lock out the use of \C by setting the
+ PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also
possible to build PCRE2 with the use of \C permanently disabled.
- PCRE2 does not allow \C to appear in lookbehind assertions (described
- below) in UTF-8 or UTF-16 modes, because this would make it impossible
- to calculate the length of the lookbehind. Neither the alternative
+ PCRE2 does not allow \C to appear in lookbehind assertions (described
+ below) in UTF-8 or UTF-16 modes, because this would make it impossible
+ to calculate the length of the lookbehind. Neither the alternative
matching function pcre2_dfa_match() nor the JIT optimizer support \C in
these UTF modes. The former gives a match-time error; the latter fails
to optimize and so the match is always run using the interpreter.
- In the 32-bit library, however, \C is always supported (when not
- explicitly locked out) because it always matches a single code unit,
+ In the 32-bit library, however, \C is always supported (when not
+ explicitly locked out) because it always matches a single code unit,
whether or not UTF-32 is specified.
In general, the \C escape sequence is best avoided. However, one way of
- using it that avoids the problem of malformed UTF-8 or UTF-16 charac-
- ters is to use a lookahead to check the length of the next character,
- as in this pattern, which could be used with a UTF-8 string (ignore
+ using it that avoids the problem of malformed UTF-8 or UTF-16 charac-
+ ters is to use a lookahead to check the length of the next character,
+ as in this pattern, which could be used with a UTF-8 string (ignore
white space and line breaks):
(?| (?=[\x00-\x7f])(\C) |
@@ -7031,10 +7045,10 @@
(?=[\x{800}-\x{ffff}])(\C)(\C)(\C) |
(?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))
- In this example, a group that starts with (?| resets the capturing
+ In this example, a group that starts with (?| resets the capturing
parentheses numbers in each alternative (see "Duplicate Subpattern Num-
bers" below). The assertions at the start of each branch check the next
- UTF-8 character for values whose encoding uses 1, 2, 3, or 4 bytes,
+ UTF-8 character for values whose encoding uses 1, 2, 3, or 4 bytes,
respectively. The character's individual bytes are then captured by the
appropriate number of \C groups.
@@ -7043,115 +7057,115 @@
An opening square bracket introduces a character class, terminated by a
closing square bracket. A closing square bracket on its own is not spe-
- cial by default. If a closing square bracket is required as a member
+ cial by default. If a closing square bracket is required as a member
of the class, it should be the first data character in the class (after
- an initial circumflex, if present) or escaped with a backslash. This
- means that, by default, an empty class cannot be defined. However, if
- the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at
+ an initial circumflex, if present) or escaped with a backslash. This
+ means that, by default, an empty class cannot be defined. However, if
+ the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at
the start does end the (empty) class.
- A character class matches a single character in the subject. A matched
+ A character class matches a single character in the subject. A matched
character must be in the set of characters defined by the class, unless
- the first character in the class definition is a circumflex, in which
+ the first character in the class definition is a circumflex, in which
case the subject character must not be in the set defined by the class.
- If a circumflex is actually required as a member of the class, ensure
+ If a circumflex is actually required as a member of the class, ensure
it is not the first character, or escape it with a backslash.
- For example, the character class [aeiou] matches any lower case vowel,
- while [^aeiou] matches any character that is not a lower case vowel.
+ For example, the character class [aeiou] matches any lower case vowel,
+ while [^aeiou] matches any character that is not a lower case vowel.
Note that a circumflex is just a convenient notation for specifying the
- characters that are in the class by enumerating those that are not. A
- class that starts with a circumflex is not an assertion; it still con-
- sumes a character from the subject string, and therefore it fails if
+ characters that are in the class by enumerating those that are not. A
+ class that starts with a circumflex is not an assertion; it still con-
+ sumes a character from the subject string, and therefore it fails if
the current pointer is at the end of the string.
- Characters in a class may be specified by their code points using \o,
- \x, or \N{U+hh..} in the usual way. When caseless matching is set, any
- letters in a class represent both their upper case and lower case ver-
- sions, so for example, a caseless [aeiou] matches "A" as well as "a",
- and a caseless [^aeiou] does not match "A", whereas a caseful version
+ Characters in a class may be specified by their code points using \o,
+ \x, or \N{U+hh..} in the usual way. When caseless matching is set, any
+ letters in a class represent both their upper case and lower case ver-
+ sions, so for example, a caseless [aeiou] matches "A" as well as "a",
+ and a caseless [^aeiou] does not match "A", whereas a caseful version
would.
- Characters that might indicate line breaks are never treated in any
- special way when matching character classes, whatever line-ending
- sequence is in use, and whatever setting of the PCRE2_DOTALL and
- PCRE2_MULTILINE options is used. A class such as [^a] always matches
+ Characters that might indicate line breaks are never treated in any
+ special way when matching character classes, whatever line-ending
+ sequence is in use, and whatever setting of the PCRE2_DOTALL and
+ PCRE2_MULTILINE options is used. A class such as [^a] always matches
one of these characters.
The generic character type escape sequences \d, \D, \h, \H, \p, \P, \s,
- \S, \v, \V, \w, and \W may appear in a character class, and add the
- characters that they match to the class. For example, [\dABCDEF]
- matches any hexadecimal digit. In UTF modes, the PCRE2_UCP option
- affects the meanings of \d, \s, \w and their upper case partners, just
- as it does when they appear outside a character class, as described in
- the section entitled "Generic character types" above. The escape
- sequence \b has a different meaning inside a character class; it
- matches the backspace character. The sequences \B, \R, and \X are not
- special inside a character class. Like any other unrecognized escape
- sequences, they cause an error. The same is true for \N when not fol-
+ \S, \v, \V, \w, and \W may appear in a character class, and add the
+ characters that they match to the class. For example, [\dABCDEF]
+ matches any hexadecimal digit. In UTF modes, the PCRE2_UCP option
+ affects the meanings of \d, \s, \w and their upper case partners, just
+ as it does when they appear outside a character class, as described in
+ the section entitled "Generic character types" above. The escape
+ sequence \b has a different meaning inside a character class; it
+ matches the backspace character. The sequences \B, \R, and \X are not
+ special inside a character class. Like any other unrecognized escape
+ sequences, they cause an error. The same is true for \N when not fol-
lowed by an opening brace.
- The minus (hyphen) character can be used to specify a range of charac-
- ters in a character class. For example, [d-m] matches any letter
- between d and m, inclusive. If a minus character is required in a
- class, it must be escaped with a backslash or appear in a position
- where it cannot be interpreted as indicating a range, typically as the
+ The minus (hyphen) character can be used to specify a range of charac-
+ ters in a character class. For example, [d-m] matches any letter
+ between d and m, inclusive. If a minus character is required in a
+ class, it must be escaped with a backslash or appear in a position
+ where it cannot be interpreted as indicating a range, typically as the
first or last character in the class, or immediately after a range. For
- example, [b-d-z] matches letters in the range b to d, a hyphen charac-
+ example, [b-d-z] matches letters in the range b to d, a hyphen charac-
ter, or z.
Perl treats a hyphen as a literal if it appears before or after a POSIX
class (see below) or before or after a character type escape such as as
- \d or \H. However, unless the hyphen is the last character in the
- class, Perl outputs a warning in its warning mode, as this is most
- likely a user error. As PCRE2 has no facility for warning, an error is
+ \d or \H. However, unless the hyphen is the last character in the
+ class, Perl outputs a warning in its warning mode, as this is most
+ likely a user error. As PCRE2 has no facility for warning, an error is
given in these cases.
It is not possible to have the literal character "]" as the end charac-
- ter of a range. A pattern such as [W-]46] is interpreted as a class of
- two characters ("W" and "-") followed by a literal string "46]", so it
- would match "W46]" or "-46]". However, if the "]" is escaped with a
- backslash it is interpreted as the end of range, so [W-\]46] is inter-
- preted as a class containing a range followed by two other characters.
- The octal or hexadecimal representation of "]" can also be used to end
+ ter of a range. A pattern such as [W-]46] is interpreted as a class of
+ two characters ("W" and "-") followed by a literal string "46]", so it
+ would match "W46]" or "-46]". However, if the "]" is escaped with a
+ backslash it is interpreted as the end of range, so [W-\]46] is inter-
+ preted as a class containing a range followed by two other characters.
+ The octal or hexadecimal representation of "]" can also be used to end
a range.
Ranges normally include all code points between the start and end char-
- acters, inclusive. They can also be used for code points specified
+ acters, inclusive. They can also be used for code points specified
numerically, for example [\000-\037]. Ranges can include any characters
- that are valid for the current mode. In any UTF mode, the so-called
- "surrogate" characters (those whose code points lie between 0xd800 and
- 0xdfff inclusive) may not be specified explicitly by default (the
- PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES option disables this check). How-
+ that are valid for the current mode. In any UTF mode, the so-called
+ "surrogate" characters (those whose code points lie between 0xd800 and
+ 0xdfff inclusive) may not be specified explicitly by default (the
+ PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES option disables this check). How-
ever, ranges such as [\x{d7ff}-\x{e000}], which include the surrogates,
are always permitted.
- There is a special case in EBCDIC environments for ranges whose end
+ There is a special case in EBCDIC environments for ranges whose end
points are both specified as literal letters in the same case. For com-
- patibility with Perl, EBCDIC code points within the range that are not
- letters are omitted. For example, [h-k] matches only four characters,
+ patibility with Perl, EBCDIC code points within the range that are not
+ letters are omitted. For example, [h-k] matches only four characters,
even though the codes for h and k are 0x88 and 0x92, a range of 11 code
- points. However, if the range is specified numerically, for example,
+ points. However, if the range is specified numerically, for example,
[\x88-\x92] or [h-\x92], all code points are included.
If a range that includes letters is used when caseless matching is set,
it matches the letters in either case. For example, [W-c] is equivalent
- to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if
- character tables for a French locale are in use, [\xc8-\xcb] matches
+ to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if
+ character tables for a French locale are in use, [\xc8-\xcb] matches
accented E characters in both cases.
- A circumflex can conveniently be used with the upper case character
- types to specify a more restricted set of characters than the matching
- lower case type. For example, the class [^\W_] matches any letter or
+ A circumflex can conveniently be used with the upper case character
+ types to specify a more restricted set of characters than the matching
+ lower case type. For example, the class [^\W_] matches any letter or
digit, but not underscore, whereas [\w] includes underscore. A positive
character class should be read as "something OR something OR ..." and a
negative class as "NOT something AND NOT something AND NOT ...".
- The only metacharacters that are recognized in character classes are
- backslash, hyphen (only where it can be interpreted as specifying a
- range), circumflex (only at the start), opening square bracket (only
- when it can be interpreted as introducing a POSIX class name, or for a
- special compatibility feature - see the next two sections), and the
+ The only metacharacters that are recognized in character classes are
+ backslash, hyphen (only where it can be interpreted as specifying a
+ range), circumflex (only at the start), opening square bracket (only
+ when it can be interpreted as introducing a POSIX class name, or for a
+ special compatibility feature - see the next two sections), and the
terminating closing square bracket. However, escaping other non-
alphanumeric characters does no harm.
@@ -7159,7 +7173,7 @@
POSIX CHARACTER CLASSES
Perl supports the POSIX notation for character classes. This uses names
- enclosed by [: and :] within the enclosing square brackets. PCRE2 also
+ enclosed by [: and :] within the enclosing square brackets. PCRE2 also
supports this notation. For example,
[01[:alpha:]%]
@@ -7182,13 +7196,13 @@
word "word" characters (same as \w)
xdigit hexadecimal digits
- The default "space" characters are HT (9), LF (10), VT (11), FF (12),
- CR (13), and space (32). If locale-specific matching is taking place,
- the list of space characters may be different; there may be fewer or
+ The default "space" characters are HT (9), LF (10), VT (11), FF (12),
+ CR (13), and space (32). If locale-specific matching is taking place,
+ the list of space characters may be different; there may be fewer or
more of them. "Space" and \s match the same set of characters.
- The name "word" is a Perl extension, and "blank" is a GNU extension
- from Perl 5.8. Another Perl extension is negation, which is indicated
+ The name "word" is a Perl extension, and "blank" is a GNU extension
+ from Perl 5.8. Another Perl extension is negation, which is indicated
by a ^ character after the colon. For example,
[12[:^digit:]]
@@ -7199,9 +7213,9 @@
By default, characters with values greater than 127 do not match any of
the POSIX character classes, although this may be different for charac-
- ters in the range 128-255 when locale-specific matching is happening.
- However, if the PCRE2_UCP option is passed to pcre2_compile(), some of
- the classes are changed so that Unicode character properties are used.
+ ters in the range 128-255 when locale-specific matching is happening.
+ However, if the PCRE2_UCP option is passed to pcre2_compile(), some of
+ the classes are changed so that Unicode character properties are used.
This is achieved by replacing certain POSIX classes with other
sequences, as follows:
@@ -7215,10 +7229,10 @@
[:upper:] becomes \p{Lu}
[:word:] becomes \p{Xwd}
- Negated versions, such as [:^alpha:] use \P instead of \p. Three other
+ Negated versions, such as [:^alpha:] use \P instead of \p. Three other
POSIX classes are handled specially in UCP mode:
- [:graph:] This matches characters that have glyphs that mark the page
+ [:graph:] This matches characters that have glyphs that mark the page
when printed. In Unicode property terms, it matches all char-
acters with the L, M, N, P, S, or Cf properties, except for:
@@ -7227,22 +7241,22 @@
U+2066 - U+2069 Various "isolate"s
- [:print:] This matches the same characters as [:graph:] plus space
- characters that are not controls, that is, characters with
+ [:print:] This matches the same characters as [:graph:] plus space
+ characters that are not controls, that is, characters with
the Zs property.
[:punct:] This matches all characters that have the Unicode P (punctua-
- tion) property, plus those characters with code points less
+ tion) property, plus those characters with code points less
than 256 that have the S (Symbol) property.
- The other POSIX classes are unchanged, and match only characters with
+ The other POSIX classes are unchanged, and match only characters with
code points less than 256.
COMPATIBILITY FEATURE FOR WORD BOUNDARIES
- In the POSIX.2 compliant library that was included in 4.4BSD Unix, the
- ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word"
+ In the POSIX.2 compliant library that was included in 4.4BSD Unix, the
+ ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word"
and "end of word". PCRE2 treats these items as follows:
[[:<:]] is converted to \b(?=\w)
@@ -7249,38 +7263,38 @@
[[:>:]] is converted to \b(?<=\w)
Only these exact character sequences are recognized. A sequence such as
- [a[:<:]b] provokes error for an unrecognized POSIX class name. This
- support is not compatible with Perl. It is provided to help migrations
+ [a[:<:]b] provokes error for an unrecognized POSIX class name. This
+ support is not compatible with Perl. It is provided to help migrations
from other environments, and is best not used in any new patterns. Note
- that \b matches at the start and the end of a word (see "Simple asser-
- tions" above), and in a Perl-style pattern the preceding or following
- character normally shows which is wanted, without the need for the
- assertions that are used above in order to give exactly the POSIX be-
+ that \b matches at the start and the end of a word (see "Simple asser-
+ tions" above), and in a Perl-style pattern the preceding or following
+ character normally shows which is wanted, without the need for the
+ assertions that are used above in order to give exactly the POSIX be-
haviour.
VERTICAL BAR
- Vertical bar characters are used to separate alternative patterns. For
+ Vertical bar characters are used to separate alternative patterns. For
example, the pattern
gilbert|sullivan
- matches either "gilbert" or "sullivan". Any number of alternatives may
- appear, and an empty alternative is permitted (matching the empty
+ matches either "gilbert" or "sullivan". Any number of alternatives may
+ appear, and an empty alternative is permitted (matching the empty
string). The matching process tries each alternative in turn, from left
- to right, and the first one that succeeds is used. If the alternatives
- are within a subpattern (defined below), "succeeds" means matching the
+ to right, and the first one that succeeds is used. If the alternatives
+ are within a subpattern (defined below), "succeeds" means matching the
rest of the main pattern as well as the alternative in the subpattern.
INTERNAL OPTION SETTING
- The settings of the PCRE2_CASELESS, PCRE2_MULTILINE, PCRE2_DOTALL,
- PCRE2_EXTENDED, PCRE2_EXTENDED_MORE, and PCRE2_NO_AUTO_CAPTURE options
- can be changed from within the pattern by a sequence of letters
- enclosed between "(?" and ")". These options are Perl-compatible, and
- are described in detail in the pcre2api documentation. The option let-
+ The settings of the PCRE2_CASELESS, PCRE2_MULTILINE, PCRE2_DOTALL,
+ PCRE2_EXTENDED, PCRE2_EXTENDED_MORE, and PCRE2_NO_AUTO_CAPTURE options
+ can be changed from within the pattern by a sequence of letters
+ enclosed between "(?" and ")". These options are Perl-compatible, and
+ are described in detail in the pcre2api documentation. The option let-
ters are:
i for PCRE2_CASELESS
@@ -7291,36 +7305,36 @@
xx for PCRE2_EXTENDED_MORE
For example, (?im) sets caseless, multiline matching. It is also possi-
- ble to unset these options by preceding the relevant letters with a
+ ble to unset these options by preceding the relevant letters with a
hyphen, for example (?-im). The two "extended" options are not indepen-
dent; unsetting either one cancels the effects of both of them.
- A combined setting and unsetting such as (?im-sx), which sets
- PCRE2_CASELESS and PCRE2_MULTILINE while unsetting PCRE2_DOTALL and
- PCRE2_EXTENDED, is also permitted. Only one hyphen may appear in the
- options string. If a letter appears both before and after the hyphen,
- the option is unset. An empty options setting "(?)" is allowed. Need-
+ A combined setting and unsetting such as (?im-sx), which sets
+ PCRE2_CASELESS and PCRE2_MULTILINE while unsetting PCRE2_DOTALL and
+ PCRE2_EXTENDED, is also permitted. Only one hyphen may appear in the
+ options string. If a letter appears both before and after the hyphen,
+ the option is unset. An empty options setting "(?)" is allowed. Need-
less to say, it has no effect.
- If the first character following (? is a circumflex, it causes all of
- the above options to be unset. Thus, (?^) is equivalent to (?-imnsx).
- Letters may follow the circumflex to cause some options to be re-
+ If the first character following (? is a circumflex, it causes all of
+ the above options to be unset. Thus, (?^) is equivalent to (?-imnsx).
+ Letters may follow the circumflex to cause some options to be re-
instated, but a hyphen may not appear.
- The PCRE2-specific options PCRE2_DUPNAMES and PCRE2_UNGREEDY can be
- changed in the same way as the Perl-compatible options by using the
+ The PCRE2-specific options PCRE2_DUPNAMES and PCRE2_UNGREEDY can be
+ changed in the same way as the Perl-compatible options by using the
characters J and U respectively. However, these are not unset by (?^).
- When one of these option changes occurs at top level (that is, not
- inside subpattern parentheses), the change applies to the remainder of
- the pattern that follows. An option change within a subpattern (see
- below for a description of subpatterns) affects only that part of the
+ When one of these option changes occurs at top level (that is, not
+ inside subpattern parentheses), the change applies to the remainder of
+ the pattern that follows. An option change within a subpattern (see
+ below for a description of subpatterns) affects only that part of the
subpattern that follows it, so
(a(?i)b)c
- matches abc and aBc and no other strings (assuming PCRE2_CASELESS is
- not used). By this means, options can be made to have different set-
+ matches abc and aBc and no other strings (assuming PCRE2_CASELESS is
+ not used). By this means, options can be made to have different set-
tings in different parts of the pattern. Any changes made in one alter-
native do carry on into subsequent branches within the same subpattern.
For example,
@@ -7327,13 +7341,13 @@
(a(?i)b|c)
- matches "ab", "aB", "c", and "C", even though when matching "C" the
- first branch is abandoned before the option setting. This is because
- the effects of option settings happen at compile time. There would be
+ matches "ab", "aB", "c", and "C", even though when matching "C" the
+ first branch is abandoned before the option setting. This is because
+ the effects of option settings happen at compile time. There would be
some very weird behaviour otherwise.
- As a convenient shorthand, if any option settings are required at the
- start of a non-capturing subpattern (see the next section), the option
+ As a convenient shorthand, if any option settings are required at the
+ start of a non-capturing subpattern (see the next section), the option
letters may appear between the "?" and the ":". Thus the two patterns
(?i:saturday|sunday)
@@ -7341,14 +7355,14 @@
match exactly the same set of strings.
- Note: There are other PCRE2-specific options that can be set by the
+ Note: There are other PCRE2-specific options that can be set by the
application when the compiling function is called. The pattern can con-
- tain special leading sequences such as (*CRLF) to override what the
- application has set or what has been defaulted. Details are given in
- the section entitled "Newline sequences" above. There are also the
- (*UTF) and (*UCP) leading sequences that can be used to set UTF and
- Unicode property modes; they are equivalent to setting the PCRE2_UTF
- and PCRE2_UCP options, respectively. However, the application can set
+ tain special leading sequences such as (*CRLF) to override what the
+ application has set or what has been defaulted. Details are given in
+ the section entitled "Newline sequences" above. There are also the
+ (*UTF) and (*UCP) leading sequences that can be used to set UTF and
+ Unicode property modes; they are equivalent to setting the PCRE2_UTF
+ and PCRE2_UCP options, respectively. However, the application can set
the PCRE2_NEVER_UTF and PCRE2_NEVER_UCP options, which lock out the use
of the (*UTF) and (*UCP) sequences.
@@ -7362,18 +7376,18 @@
cat(aract|erpillar|)
- matches "cataract", "caterpillar", or "cat". Without the parentheses,
+ matches "cataract", "caterpillar", or "cat". Without the parentheses,
it would match "cataract", "erpillar" or an empty string.
- 2. It sets up the subpattern as a capturing subpattern. This means
+ 2. It sets up the subpattern as a capturing subpattern. This means
that, when the whole pattern matches, the portion of the subject string
- that matched the subpattern is passed back to the caller, separately
- from the portion that matched the whole pattern. (This applies only to
- the traditional matching function; the DFA matching function does not
+ that matched the subpattern is passed back to the caller, separately
+ from the portion that matched the whole pattern. (This applies only to
+ the traditional matching function; the DFA matching function does not
support capturing.)
Opening parentheses are counted from left to right (starting from 1) to
- obtain numbers for the capturing subpatterns. For example, if the
+ obtain numbers for the capturing subpatterns. For example, if the
string "the red king" is matched against the pattern
the ((red|white) (king|queen))
@@ -7381,12 +7395,12 @@
the captured substrings are "red king", "red", and "king", and are num-
bered 1, 2, and 3, respectively.
- The fact that plain parentheses fulfil two functions is not always
- helpful. There are often times when a grouping subpattern is required
- without a capturing requirement. If an opening parenthesis is followed
- by a question mark and a colon, the subpattern does not do any captur-
- ing, and is not counted when computing the number of any subsequent
- capturing subpatterns. For example, if the string "the white queen" is
+ The fact that plain parentheses fulfil two functions is not always
+ helpful. There are often times when a grouping subpattern is required
+ without a capturing requirement. If an opening parenthesis is followed
+ by a question mark and a colon, the subpattern does not do any captur-
+ ing, and is not counted when computing the number of any subsequent
+ capturing subpatterns. For example, if the string "the white queen" is
matched against the pattern
the ((?:red|white) (king|queen))
@@ -7394,8 +7408,8 @@
the captured substrings are "white queen" and "queen", and are numbered
1 and 2. The maximum number of capturing subpatterns is 65535.
- As a convenient shorthand, if any option settings are required at the
- start of a non-capturing subpattern, the option letters may appear
+ As a convenient shorthand, if any option settings are required at the
+ start of a non-capturing subpattern, the option letters may appear
between the "?" and the ":". Thus the two patterns
(?i:saturday|sunday)
@@ -7402,9 +7416,9 @@
(?:(?i)saturday|sunday)
match exactly the same set of strings. Because alternative branches are
- tried from left to right, and options are not reset until the end of
- the subpattern is reached, an option setting in one branch does affect
- subsequent branches, so the above patterns match "SUNDAY" as well as
+ tried from left to right, and options are not reset until the end of
+ the subpattern is reached, an option setting in one branch does affect
+ subsequent branches, so the above patterns match "SUNDAY" as well as
"Saturday".
@@ -7411,20 +7425,20 @@
DUPLICATE SUBPATTERN NUMBERS
Perl 5.10 introduced a feature whereby each alternative in a subpattern
- uses the same numbers for its capturing parentheses. Such a subpattern
- starts with (?| and is itself a non-capturing subpattern. For example,
+ uses the same numbers for its capturing parentheses. Such a subpattern
+ starts with (?| and is itself a non-capturing subpattern. For example,
consider this pattern:
(?|(Sat)ur|(Sun))day
- Because the two alternatives are inside a (?| group, both sets of cap-
- turing parentheses are numbered one. Thus, when the pattern matches,
- you can look at captured substring number one, whichever alternative
- matched. This construct is useful when you want to capture part, but
+ Because the two alternatives are inside a (?| group, both sets of cap-
+ turing parentheses are numbered one. Thus, when the pattern matches,
+ you can look at captured substring number one, whichever alternative
+ matched. This construct is useful when you want to capture part, but
not all, of one of a number of alternatives. Inside a (?| group, paren-
- theses are numbered as usual, but the number is reset at the start of
- each branch. The numbers of any capturing parentheses that follow the
- subpattern start after the highest number used in any branch. The fol-
+ theses are numbered as usual, but the number is reset at the start of
+ each branch. The numbers of any capturing parentheses that follow the
+ subpattern start after the highest number used in any branch. The fol-
lowing example is taken from the Perl documentation. The numbers under-
neath show in which buffer the captured content will be stored.
@@ -7432,14 +7446,14 @@
/ ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
# 1 2 2 3 2 3 4
- A backreference to a numbered subpattern uses the most recent value
- that is set for that number by any subpattern. The following pattern
+ A backreference to a numbered subpattern uses the most recent value
+ that is set for that number by any subpattern. The following pattern
matches "abcabc" or "defdef":
/(?|(abc)|(def))\1/
- In contrast, a subroutine call to a numbered subpattern always refers
- to the first one in the pattern with the given number. The following
+ In contrast, a subroutine call to a numbered subpattern always refers
+ to the first one in the pattern with the given number. The following
pattern matches "abcabc" or "defabc":
/(?|(abc)|(def))(?1)/
@@ -7447,65 +7461,65 @@
A relative reference such as (?-1) is no different: it is just a conve-
nient way of computing an absolute group number.
- If a condition test for a subpattern's having matched refers to a non-
- unique number, the test is true if any of the subpatterns of that num-
+ If a condition test for a subpattern's having matched refers to a non-
+ unique number, the test is true if any of the subpatterns of that num-
ber have matched.
- An alternative approach to using this "branch reset" feature is to use
+ An alternative approach to using this "branch reset" feature is to use
duplicate named subpatterns, as described in the next section.
NAMED SUBPATTERNS
- Identifying capturing parentheses by number is simple, but it can be
- very hard to keep track of the numbers in complicated patterns. Fur-
+ Identifying capturing parentheses by number is simple, but it can be
+ very hard to keep track of the numbers in complicated patterns. Fur-
thermore, if an expression is modified, the numbers may change. To help
- with this difficulty, PCRE2 supports the naming of capturing subpat-
- terns. This feature was not added to Perl until release 5.10. Python
- had the feature earlier, and PCRE1 introduced it at release 4.0, using
+ with this difficulty, PCRE2 supports the naming of capturing subpat-
+ terns. This feature was not added to Perl until release 5.10. Python
+ had the feature earlier, and PCRE1 introduced it at release 4.0, using
the Python syntax. PCRE2 supports both the Perl and the Python syntax.
- In PCRE2, a capturing subpattern can be named in one of three ways:
+ In PCRE2, a capturing subpattern can be named in one of three ways:
(?<name>...) or (?'name'...) as in Perl, or (?P<name>...) as in Python.
- Names consist of up to 32 alphanumeric characters and underscores, but
- must start with a non-digit. References to capturing parentheses from
+ Names consist of up to 32 alphanumeric characters and underscores, but
+ must start with a non-digit. References to capturing parentheses from
other parts of the pattern, such as backreferences, recursion, and con-
ditions, can all be made by name as well as by number.
- Named capturing parentheses are allocated numbers as well as names,
- exactly as if the names were not present. In both PCRE2 and Perl, cap-
- turing subpatterns are primarily identified by numbers; any names are
- just aliases for these numbers. The PCRE2 API provides function calls
- for extracting the complete name-to-number translation table from a
- compiled pattern, as well as convenience functions for extracting cap-
+ Named capturing parentheses are allocated numbers as well as names,
+ exactly as if the names were not present. In both PCRE2 and Perl, cap-
+ turing subpatterns are primarily identified by numbers; any names are
+ just aliases for these numbers. The PCRE2 API provides function calls
+ for extracting the complete name-to-number translation table from a
+ compiled pattern, as well as convenience functions for extracting cap-
tured substrings by name.
- Warning: When more than one subpattern has the same number, as
- described in the previous section, a name given to one of them applies
- to all of them. Perl allows identically numbered subpatterns to have
- different names. Consider this pattern, where there are two capturing
+ Warning: When more than one subpattern has the same number, as
+ described in the previous section, a name given to one of them applies
+ to all of them. Perl allows identically numbered subpatterns to have
+ different names. Consider this pattern, where there are two capturing
subpatterns, both numbered 1:
(?|(?<AA>aa)|(?<BB>bb))
- Perl allows this, with both names AA and BB as aliases of group 1.
+ Perl allows this, with both names AA and BB as aliases of group 1.
Thus, after a successful match, both names yield the same value (either
"aa" or "bb").
- In an attempt to reduce confusion, PCRE2 does not allow the same group
+ In an attempt to reduce confusion, PCRE2 does not allow the same group
number to be associated with more than one name. The example above pro-
- vokes a compile-time error. However, there is still scope for confu-
+ vokes a compile-time error. However, there is still scope for confu-
sion. Consider this pattern:
(?|(?<AA>aa)|(bb))
- Although the second subpattern number 1 is not explicitly named, the
+ Although the second subpattern number 1 is not explicitly named, the
name AA is still an alias for subpattern 1. Whether the pattern matches
- "aa" or "bb", a reference by name to group AA yields the matched
+ "aa" or "bb", a reference by name to group AA yields the matched
string.
- By default, a name must be unique within a pattern, except that dupli-
- cate names are permitted for subpatterns with the same number, for
+ By default, a name must be unique within a pattern, except that dupli-
+ cate names are permitted for subpatterns with the same number, for
example:
(?|(?<AA>aa)|(?<AA>bb))
@@ -7512,10 +7526,10 @@
The duplicate name constraint can be disabled by setting the PCRE2_DUP-
NAMES option at compile time, or by the use of (?J) within the pattern.
- Duplicate names can be useful for patterns where only one instance of
- the named parentheses can match. Suppose you want to match the name of
- a weekday, either as a 3-letter abbreviation or as the full name, and
- in both cases you want to extract the abbreviation. This pattern
+ Duplicate names can be useful for patterns where only one instance of
+ the named parentheses can match. Suppose you want to match the name of
+ a weekday, either as a 3-letter abbreviation or as the full name, and
+ in both cases you want to extract the abbreviation. This pattern
(ignoring the line breaks) does the job:
(?<DN>Mon|Fri|Sun)(?:day)?|
@@ -7524,17 +7538,17 @@
(?<DN>Thu)(?:rsday)?|
(?<DN>Sat)(?:urday)?
- There are five capturing substrings, but only one is ever set after a
- match. The convenience functions for extracting the data by name
- returns the substring for the first (and in this example, the only)
- subpattern of that name that matched. This saves searching to find
- which numbered subpattern it was. (An alternative way of solving this
+ There are five capturing substrings, but only one is ever set after a
+ match. The convenience functions for extracting the data by name
+ returns the substring for the first (and in this example, the only)
+ subpattern of that name that matched. This saves searching to find
+ which numbered subpattern it was. (An alternative way of solving this
problem is to use a "branch reset" subpattern, as described in the pre-
vious section.)
If you make a backreference to a non-unique named subpattern from else-
- where in the pattern, the subpatterns to which the name refers are
- checked in the order in which they appear in the overall pattern. The
+ where in the pattern, the subpatterns to which the name refers are
+ checked in the order in which they appear in the overall pattern. The
first one that is set is used for the reference. For example, this pat-
tern matches both "foofoo" and "barbar" but not "foobar" or "barfoo":
@@ -7542,21 +7556,21 @@
If you make a subroutine call to a non-unique named subpattern, the one
- that corresponds to the first occurrence of the name is used. In the
+ that corresponds to the first occurrence of the name is used. In the
absence of duplicate numbers this is the one with the lowest number.
If you use a named reference in a condition test (see the section about
conditions below), either to check whether a subpattern has matched, or
- to check for recursion, all subpatterns with the same name are tested.
- If the condition is true for any one of them, the overall condition is
- true. This is the same behaviour as testing by number. For further
- details of the interfaces for handling named subpatterns, see the
+ to check for recursion, all subpatterns with the same name are tested.
+ If the condition is true for any one of them, the overall condition is
+ true. This is the same behaviour as testing by number. For further
+ details of the interfaces for handling named subpatterns, see the
pcre2api documentation.
REPETITION
- Repetition is specified by quantifiers, which can follow any of the
+ Repetition is specified by quantifiers, which can follow any of the
following items:
a literal data character
@@ -7570,17 +7584,17 @@
a parenthesized subpattern (including most assertions)
a subroutine call to a subpattern (recursive or otherwise)
- The general repetition quantifier specifies a minimum and maximum num-
- ber of permitted matches, by giving the two numbers in curly brackets
- (braces), separated by a comma. The numbers must be less than 65536,
+ The general repetition quantifier specifies a minimum and maximum num-
+ ber of permitted matches, by giving the two numbers in curly brackets
+ (braces), separated by a comma. The numbers must be less than 65536,
and the first must be less than or equal to the second. For example:
z{2,4}
- matches "zz", "zzz", or "zzzz". A closing brace on its own is not a
- special character. If the second number is omitted, but the comma is
- present, there is no upper limit; if the second number and the comma
- are both omitted, the quantifier specifies an exact number of required
+ matches "zz", "zzz", or "zzzz". A closing brace on its own is not a
+ special character. If the second number is omitted, but the comma is
+ present, there is no upper limit; if the second number and the comma
+ are both omitted, the quantifier specifies an exact number of required
matches. Thus
[aeiou]{3,}
@@ -7589,26 +7603,26 @@
\d{8}
- matches exactly 8 digits. An opening curly bracket that appears in a
- position where a quantifier is not allowed, or one that does not match
- the syntax of a quantifier, is taken as a literal character. For exam-
+ matches exactly 8 digits. An opening curly bracket that appears in a
+ position where a quantifier is not allowed, or one that does not match
+ the syntax of a quantifier, is taken as a literal character. For exam-
ple, {,6} is not a quantifier, but a literal string of four characters.
In UTF modes, quantifiers apply to characters rather than to individual
- code units. Thus, for example, \x{100}{2} matches two characters, each
+ code units. Thus, for example, \x{100}{2} matches two characters, each
of which is represented by a two-byte sequence in a UTF-8 string. Simi-
- larly, \X{3} matches three Unicode extended grapheme clusters, each of
- which may be several code units long (and they may be of different
+ larly, \X{3} matches three Unicode extended grapheme clusters, each of
+ which may be several code units long (and they may be of different
lengths).
The quantifier {0} is permitted, causing the expression to behave as if
the previous item and the quantifier were not present. This may be use-
- ful for subpatterns that are referenced as subroutines from elsewhere
+ ful for subpatterns that are referenced as subroutines from elsewhere
in the pattern (but see also the section entitled "Defining subpatterns
- for use by reference only" below). Items other than subpatterns that
+ for use by reference only" below). Items other than subpatterns that
have a {0} quantifier are omitted from the compiled pattern.
- For convenience, the three most common quantifiers have single-charac-
+ For convenience, the three most common quantifiers have single-charac-
ter abbreviations:
* is equivalent to {0,}
@@ -7615,24 +7629,24 @@
+ is equivalent to {1,}
? is equivalent to {0,1}
- It is possible to construct infinite loops by following a subpattern
+ It is possible to construct infinite loops by following a subpattern
that can match no characters with a quantifier that has no upper limit,
for example:
(a?)*
- Earlier versions of Perl and PCRE1 used to give an error at compile
+ Earlier versions of Perl and PCRE1 used to give an error at compile
time for such patterns. However, because there are cases where this can
be useful, such patterns are now accepted, but if any repetition of the
- subpattern does in fact match no characters, the loop is forcibly bro-
+ subpattern does in fact match no characters, the loop is forcibly bro-
ken.
- By default, the quantifiers are "greedy", that is, they match as much
- as possible (up to the maximum number of permitted times), without
- causing the rest of the pattern to fail. The classic example of where
+ By default, the quantifiers are "greedy", that is, they match as much
+ as possible (up to the maximum number of permitted times), without
+ causing the rest of the pattern to fail. The classic example of where
this gives problems is in trying to match comments in C programs. These
- appear between /* and */ and within the comment, individual * and /
- characters may appear. An attempt to match C comments by applying the
+ appear between /* and */ and within the comment, individual * and /
+ characters may appear. An attempt to match C comments by applying the
pattern
/\*.*\*/
@@ -7641,19 +7655,19 @@
/* first comment */ not comment /* second comment */
- fails, because it matches the entire string owing to the greediness of
+ fails, because it matches the entire string owing to the greediness of
the .* item.
If a quantifier is followed by a question mark, it ceases to be greedy,
- and instead matches the minimum number of times possible, so the pat-
+ and instead matches the minimum number of times possible, so the pat-
tern
/\*.*?\*/
- does the right thing with the C comments. The meaning of the various
- quantifiers is not otherwise changed, just the preferred number of
- matches. Do not confuse this use of question mark with its use as a
- quantifier in its own right. Because it has two uses, it can sometimes
+ does the right thing with the C comments. The meaning of the various
+ quantifiers is not otherwise changed, just the preferred number of
+ matches. Do not confuse this use of question mark with its use as a
+ quantifier in its own right. Because it has two uses, it can sometimes
appear doubled, as in
\d??\d
@@ -7662,45 +7676,45 @@
only way the rest of the pattern matches.
If the PCRE2_UNGREEDY option is set (an option that is not available in
- Perl), the quantifiers are not greedy by default, but individual ones
- can be made greedy by following them with a question mark. In other
+ Perl), the quantifiers are not greedy by default, but individual ones
+ can be made greedy by following them with a question mark. In other
words, it inverts the default behaviour.
- When a parenthesized subpattern is quantified with a minimum repeat
- count that is greater than 1 or with a limited maximum, more memory is
- required for the compiled pattern, in proportion to the size of the
+ When a parenthesized subpattern is quantified with a minimum repeat
+ count that is greater than 1 or with a limited maximum, more memory is
+ required for the compiled pattern, in proportion to the size of the
minimum or maximum.
- If a pattern starts with .* or .{0,} and the PCRE2_DOTALL option
- (equivalent to Perl's /s) is set, thus allowing the dot to match new-
- lines, the pattern is implicitly anchored, because whatever follows
- will be tried against every character position in the subject string,
- so there is no point in retrying the overall match at any position
+ If a pattern starts with .* or .{0,} and the PCRE2_DOTALL option
+ (equivalent to Perl's /s) is set, thus allowing the dot to match new-
+ lines, the pattern is implicitly anchored, because whatever follows
+ will be tried against every character position in the subject string,
+ so there is no point in retrying the overall match at any position
after the first. PCRE2 normally treats such a pattern as though it were
preceded by \A.
- In cases where it is known that the subject string contains no new-
- lines, it is worth setting PCRE2_DOTALL in order to obtain this opti-
+ In cases where it is known that the subject string contains no new-
+ lines, it is worth setting PCRE2_DOTALL in order to obtain this opti-
mization, or alternatively, using ^ to indicate anchoring explicitly.
- However, there are some cases where the optimization cannot be used.
- When .* is inside capturing parentheses that are the subject of a
- backreference elsewhere in the pattern, a match at the start may fail
+ However, there are some cases where the optimization cannot be used.
+ When .* is inside capturing parentheses that are the subject of a
+ backreference elsewhere in the pattern, a match at the start may fail
where a later one succeeds. Consider, for example:
(.*)abc\1
- If the subject is "xyz123abc123" the match point is the fourth charac-
+ If the subject is "xyz123abc123" the match point is the fourth charac-
ter. For this reason, such a pattern is not implicitly anchored.
- Another case where implicit anchoring is not applied is when the lead-
- ing .* is inside an atomic group. Once again, a match at the start may
+ Another case where implicit anchoring is not applied is when the lead-
+ ing .* is inside an atomic group. Once again, a match at the start may
fail where a later one succeeds. Consider this pattern:
(?>.*?a)b
- It matches "ab" in the subject "aab". The use of the backtracking con-
- trol verbs (*PRUNE) and (*SKIP) also disable this optimization, and
+ It matches "ab" in the subject "aab". The use of the backtracking con-
+ trol verbs (*PRUNE) and (*SKIP) also disable this optimization, and
there is an option, PCRE2_NO_DOTSTAR_ANCHOR, to do so explicitly.
When a capturing subpattern is repeated, the value captured is the sub-
@@ -7709,8 +7723,8 @@
(tweedle[dume]{3}\s*)+
has matched "tweedledum tweedledee" the value of the captured substring
- is "tweedledee". However, if there are nested capturing subpatterns,
- the corresponding captured values may have been set in previous itera-
+ is "tweedledee". However, if there are nested capturing subpatterns,
+ the corresponding captured values may have been set in previous itera-
tions. For example, after
(a|(b))+
@@ -7720,53 +7734,53 @@
ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
- With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
- repetition, failure of what follows normally causes the repeated item
- to be re-evaluated to see if a different number of repeats allows the
- rest of the pattern to match. Sometimes it is useful to prevent this,
- either to change the nature of the match, or to cause it fail earlier
- than it otherwise might, when the author of the pattern knows there is
+ With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
+ repetition, failure of what follows normally causes the repeated item
+ to be re-evaluated to see if a different number of repeats allows the
+ rest of the pattern to match. Sometimes it is useful to prevent this,
+ either to change the nature of the match, or to cause it fail earlier
+ than it otherwise might, when the author of the pattern knows there is
no point in carrying on.
- Consider, for example, the pattern \d+foo when applied to the subject
+ Consider, for example, the pattern \d+foo when applied to the subject
line
123456bar
After matching all 6 digits and then failing to match "foo", the normal
- action of the matcher is to try again with only 5 digits matching the
- \d+ item, and then with 4, and so on, before ultimately failing.
- "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides
- the means for specifying that once a subpattern has matched, it is not
+ action of the matcher is to try again with only 5 digits matching the
+ \d+ item, and then with 4, and so on, before ultimately failing.
+ "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides
+ the means for specifying that once a subpattern has matched, it is not
to be re-evaluated in this way.
- If we use atomic grouping for the previous example, the matcher gives
- up immediately on failing to match "foo" the first time. The notation
+ If we use atomic grouping for the previous example, the matcher gives
+ up immediately on failing to match "foo" the first time. The notation
is a kind of special parenthesis, starting with (?> as in this example:
(?>\d+)foo
- This kind of parenthesis "locks up" the part of the pattern it con-
- tains once it has matched, and a failure further into the pattern is
- prevented from backtracking into it. Backtracking past it to previous
+ This kind of parenthesis "locks up" the part of the pattern it con-
+ tains once it has matched, and a failure further into the pattern is
+ prevented from backtracking into it. Backtracking past it to previous
items, however, works as normal.
- An alternative description is that a subpattern of this type matches
- exactly the string of characters that an identical standalone pattern
+ An alternative description is that a subpattern of this type matches
+ exactly the string of characters that an identical standalone pattern
would match, if anchored at the current point in the subject string.
Atomic grouping subpatterns are not capturing subpatterns. Simple cases
such as the above example can be thought of as a maximizing repeat that
- must swallow everything it can. So, while both \d+ and \d+? are pre-
- pared to adjust the number of digits they match in order to make the
+ must swallow everything it can. So, while both \d+ and \d+? are pre-
+ pared to adjust the number of digits they match in order to make the
rest of the pattern match, (?>\d+) can only match an entire sequence of
digits.
- Atomic groups in general can of course contain arbitrarily complicated
- subpatterns, and can be nested. However, when the subpattern for an
+ Atomic groups in general can of course contain arbitrarily complicated
+ subpatterns, and can be nested. However, when the subpattern for an
atomic group is just a single repeated item, as in the example above, a
- simpler notation, called a "possessive quantifier" can be used. This
- consists of an additional + character following a quantifier. Using
+ simpler notation, called a "possessive quantifier" can be used. This
+ consists of an additional + character following a quantifier. Using
this notation, the previous example can be rewritten as
\d++foo
@@ -7776,46 +7790,46 @@
(abc|xyz){2,3}+
- Possessive quantifiers are always greedy; the setting of the
- PCRE2_UNGREEDY option is ignored. They are a convenient notation for
- the simpler forms of atomic group. However, there is no difference in
+ Possessive quantifiers are always greedy; the setting of the
+ PCRE2_UNGREEDY option is ignored. They are a convenient notation for
+ the simpler forms of atomic group. However, there is no difference in
the meaning of a possessive quantifier and the equivalent atomic group,
- though there may be a performance difference; possessive quantifiers
+ though there may be a performance difference; possessive quantifiers
should be slightly faster.
- The possessive quantifier syntax is an extension to the Perl 5.8 syn-
- tax. Jeffrey Friedl originated the idea (and the name) in the first
+ The possessive quantifier syntax is an extension to the Perl 5.8 syn-
+ tax. Jeffrey Friedl originated the idea (and the name) in the first
edition of his book. Mike McCloskey liked it, so implemented it when he
built Sun's Java package, and PCRE1 copied it from there. It ultimately
found its way into Perl at release 5.10.
- PCRE2 has an optimization that automatically "possessifies" certain
- simple pattern constructs. For example, the sequence A+B is treated as
- A++B because there is no point in backtracking into a sequence of A's
+ PCRE2 has an optimization that automatically "possessifies" certain
+ simple pattern constructs. For example, the sequence A+B is treated as
+ A++B because there is no point in backtracking into a sequence of A's
when B must follow. This feature can be disabled by the PCRE2_NO_AUTO-
POSSESS option, or starting the pattern with (*NO_AUTO_POSSESS).
- When a pattern contains an unlimited repeat inside a subpattern that
- can itself be repeated an unlimited number of times, the use of an
- atomic group is the only way to avoid some failing matches taking a
+ When a pattern contains an unlimited repeat inside a subpattern that
+ can itself be repeated an unlimited number of times, the use of an
+ atomic group is the only way to avoid some failing matches taking a
very long time indeed. The pattern
(\D+|<\d+>)*[!?]
- matches an unlimited number of substrings that either consist of non-
- digits, or digits enclosed in <>, followed by either ! or ?. When it
+ matches an unlimited number of substrings that either consist of non-
+ digits, or digits enclosed in <>, followed by either ! or ?. When it
matches, it runs quickly. However, if it is applied to
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
- it takes a long time before reporting failure. This is because the
- string can be divided between the internal \D+ repeat and the external
- * repeat in a large number of ways, and all have to be tried. (The
- example uses [!?] rather than a single character at the end, because
- both PCRE2 and Perl have an optimization that allows for fast failure
- when a single character is used. They remember the last single charac-
- ter that is required for a match, and fail early if it is not present
- in the string.) If the pattern is changed so that it uses an atomic
+ it takes a long time before reporting failure. This is because the
+ string can be divided between the internal \D+ repeat and the external
+ * repeat in a large number of ways, and all have to be tried. (The
+ example uses [!?] rather than a single character at the end, because
+ both PCRE2 and Perl have an optimization that allows for fast failure
+ when a single character is used. They remember the last single charac-
+ ter that is required for a match, and fail early if it is not present
+ in the string.) If the pattern is changed so that it uses an atomic
group, like this:
((?>\D+)|<\d+>)*[!?]
@@ -7826,29 +7840,29 @@
BACKREFERENCES
Outside a character class, a backslash followed by a digit greater than
- 0 (and possibly further digits) is a backreference to a capturing sub-
- pattern earlier (that is, to its left) in the pattern, provided there
+ 0 (and possibly further digits) is a backreference to a capturing sub-
+ pattern earlier (that is, to its left) in the pattern, provided there
have been that many previous capturing left parentheses.
- However, if the decimal number following the backslash is less than 8,
- it is always taken as a backreference, and causes an error only if
- there are not that many capturing left parentheses in the entire pat-
- tern. In other words, the parentheses that are referenced need not be
- to the left of the reference for numbers less than 8. A "forward back-
- reference" of this type can make sense when a repetition is involved
- and the subpattern to the right has participated in an earlier itera-
+ However, if the decimal number following the backslash is less than 8,
+ it is always taken as a backreference, and causes an error only if
+ there are not that many capturing left parentheses in the entire pat-
+ tern. In other words, the parentheses that are referenced need not be
+ to the left of the reference for numbers less than 8. A "forward back-
+ reference" of this type can make sense when a repetition is involved
+ and the subpattern to the right has participated in an earlier itera-
tion.
- It is not possible to have a numerical "forward backreference" to a
- subpattern whose number is 8 or more using this syntax because a
- sequence such as \50 is interpreted as a character defined in octal.
+ It is not possible to have a numerical "forward backreference" to a
+ subpattern whose number is 8 or more using this syntax because a
+ sequence such as \50 is interpreted as a character defined in octal.
See the subsection entitled "Non-printing characters" above for further
- details of the handling of digits following a backslash. There is no
- such problem when named parentheses are used. A backreference to any
+ details of the handling of digits following a backslash. There is no
+ such problem when named parentheses are used. A backreference to any
subpattern is possible using named parentheses (see below).
- Another way of avoiding the ambiguity inherent in the use of digits
- following a backslash is to use the \g escape sequence. This escape
+ Another way of avoiding the ambiguity inherent in the use of digits
+ following a backslash is to use the \g escape sequence. This escape
must be followed by a signed or unsigned number, optionally enclosed in
braces. These examples are all identical:
@@ -7856,9 +7870,9 @@
(ring), \g1
(ring), \g{1}
- An unsigned number specifies an absolute reference without the ambigu-
+ An unsigned number specifies an absolute reference without the ambigu-
ity that is present in the older syntax. It is also useful when literal
- digits follow the reference. A signed number is a relative reference.
+ digits follow the reference. A signed number is a relative reference.
Consider this example:
(abc(def)ghi)\g{-1}
@@ -7865,37 +7879,37 @@
The sequence \g{-1} is a reference to the most recently started captur-
ing subpattern before \g, that is, is it equivalent to \2 in this exam-
- ple. Similarly, \g{-2} would be equivalent to \1. The use of relative
- references can be helpful in long patterns, and also in patterns that
- are created by joining together fragments that contain references
+ ple. Similarly, \g{-2} would be equivalent to \1. The use of relative
+ references can be helpful in long patterns, and also in patterns that
+ are created by joining together fragments that contain references
within themselves.
- The sequence \g{+1} is a reference to the next capturing subpattern.
- This kind of forward reference can be useful it patterns that repeat.
+ The sequence \g{+1} is a reference to the next capturing subpattern.
+ This kind of forward reference can be useful it patterns that repeat.
Perl does not support the use of + in this way.
A backreference matches whatever actually matched the capturing subpat-
- tern in the current subject string, rather than anything matching the
- subpattern itself (see "Subpatterns as subroutines" below for a way of
+ tern in the current subject string, rather than anything matching the
+ subpattern itself (see "Subpatterns as subroutines" below for a way of
doing that). So the pattern
(sens|respons)e and \1ibility
- matches "sense and sensibility" and "response and responsibility", but
- not "sense and responsibility". If caseful matching is in force at the
- time of the backreference, the case of letters is relevant. For exam-
+ matches "sense and sensibility" and "response and responsibility", but
+ not "sense and responsibility". If caseful matching is in force at the
+ time of the backreference, the case of letters is relevant. For exam-
ple,
((?i)rah)\s+\1
- matches "rah rah" and "RAH RAH", but not "RAH rah", even though the
+ matches "rah rah" and "RAH RAH", but not "RAH rah", even though the
original capturing subpattern is matched caselessly.
- There are several different ways of writing backreferences to named
- subpatterns. The .NET syntax \k{name} and the Perl syntax \k<name> or
- \k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's
- unified backreference syntax, in which \g can be used for both numeric
- and named references, is also supported. We could rewrite the above
+ There are several different ways of writing backreferences to named
+ subpatterns. The .NET syntax \k{name} and the Perl syntax \k<name> or
+ \k'name' are supported, as is the Python syntax (?P=name). Perl 5.10's
+ unified backreference syntax, in which \g can be used for both numeric
+ and named references, is also supported. We could rewrite the above
example in any of the following ways:
(?<p1>(?i)rah)\s+\k<p1>
@@ -7903,32 +7917,32 @@
(?P<p1>(?i)rah)\s+(?P=p1)
(?<p1>(?i)rah)\s+\g{p1}
- A subpattern that is referenced by name may appear in the pattern
+ A subpattern that is referenced by name may appear in the pattern
before or after the reference.
- There may be more than one backreference to the same subpattern. If a
- subpattern has not actually been used in a particular match, any back-
+ There may be more than one backreference to the same subpattern. If a
+ subpattern has not actually been used in a particular match, any back-
references to it always fail by default. For example, the pattern
(a|(bc))\2
- always fails if it starts to match "a" rather than "bc". However, if
+ always fails if it starts to match "a" rather than "bc". However, if
the PCRE2_MATCH_UNSET_BACKREF option is set at compile time, a backref-
erence to an unset value matches an empty string.
- Because there may be many capturing parentheses in a pattern, all dig-
- its following a backslash are taken as part of a potential backrefer-
- ence number. If the pattern continues with a digit character, some
- delimiter must be used to terminate the backreference. If the
- PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, this can be white
- space. Otherwise, the \g{ syntax or an empty comment (see "Comments"
+ Because there may be many capturing parentheses in a pattern, all dig-
+ its following a backslash are taken as part of a potential backrefer-
+ ence number. If the pattern continues with a digit character, some
+ delimiter must be used to terminate the backreference. If the
+ PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, this can be white
+ space. Otherwise, the \g{ syntax or an empty comment (see "Comments"
below) can be used.
Recursive backreferences
- A backreference that occurs inside the parentheses to which it refers
- fails when the subpattern is first used, so, for example, (a\1) never
- matches. However, such references can be useful inside repeated sub-
+ A backreference that occurs inside the parentheses to which it refers
+ fails when the subpattern is first used, so, for example, (a\1) never
+ matches. However, such references can be useful inside repeated sub-
patterns. For example, the pattern
(a|b\1)+
@@ -7936,74 +7950,74 @@
matches any number of "a"s and also "aba", "ababbaa" etc. At each iter-
ation of the subpattern, the backreference matches the character string
corresponding to the previous iteration. In order for this to work, the
- pattern must be such that the first iteration does not need to match
- the backreference. This can be done using alternation, as in the exam-
+ pattern must be such that the first iteration does not need to match
+ the backreference. This can be done using alternation, as in the exam-
ple above, or by a quantifier with a minimum of zero.
- Backreferences of this type cause the group that they reference to be
- treated as an atomic group. Once the whole group has been matched, a
- subsequent matching failure cannot cause backtracking into the middle
+ Backreferences of this type cause the group that they reference to be
+ treated as an atomic group. Once the whole group has been matched, a
+ subsequent matching failure cannot cause backtracking into the middle
of the group.
ASSERTIONS
- An assertion is a test on the characters following or preceding the
+ An assertion is a test on the characters following or preceding the
current matching point that does not consume any characters. The simple
- assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described
+ assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described
above.
- More complicated assertions are coded as subpatterns. There are two
- kinds: those that look ahead of the current position in the subject
- string, and those that look behind it, and in each case an assertion
- may be positive (must succeed for matching to continue) or negative
+ More complicated assertions are coded as subpatterns. There are two
+ kinds: those that look ahead of the current position in the subject
+ string, and those that look behind it, and in each case an assertion
+ may be positive (must succeed for matching to continue) or negative
(must not succeed for matching to continue). An assertion subpattern is
matched in the normal way, except that, when matching continues after a
successful assertion, the matching position in the subject string is as
it was before the assertion was processed.
- Assertion subpatterns are not capturing subpatterns. If an assertion
- contains capturing subpatterns within it, these are counted for the
- purposes of numbering the capturing subpatterns in the whole pattern.
- Within each branch of an assertion, locally captured substrings may be
+ Assertion subpatterns are not capturing subpatterns. If an assertion
+ contains capturing subpatterns within it, these are counted for the
+ purposes of numbering the capturing subpatterns in the whole pattern.
+ Within each branch of an assertion, locally captured substrings may be
referenced in the usual way. For example, a sequence such as (.)\g{-1}
can be used to check that two adjacent characters are the same.
- When a branch within an assertion fails to match, any substrings that
- were captured are discarded (as happens with any pattern branch that
- fails to match). A negative assertion succeeds only when all its
+ When a branch within an assertion fails to match, any substrings that
+ were captured are discarded (as happens with any pattern branch that
+ fails to match). A negative assertion succeeds only when all its
branches fail to match; this means that no captured substrings are ever
- retained after a successful negative assertion. When an assertion con-
+ retained after a successful negative assertion. When an assertion con-
tains a matching branch, what happens depends on the type of assertion.
- For a positive assertion, internally captured substrings in the suc-
- cessful branch are retained, and matching continues with the next pat-
- tern item after the assertion. For a negative assertion, a matching
- branch means that the assertion has failed. If the assertion is being
- used as a condition in a conditional subpattern (see below), captured
- substrings are retained, because matching continues with the "no"
+ For a positive assertion, internally captured substrings in the suc-
+ cessful branch are retained, and matching continues with the next pat-
+ tern item after the assertion. For a negative assertion, a matching
+ branch means that the assertion has failed. If the assertion is being
+ used as a condition in a conditional subpattern (see below), captured
+ substrings are retained, because matching continues with the "no"
branch of the condition. For other failing negative assertions, control
passes to the previous backtracking point, thus discarding any captured
strings within the assertion.
- For compatibility with Perl, most assertion subpatterns may be
- repeated; though it makes no sense to assert the same thing several
- times, the side effect of capturing parentheses may occasionally be
- useful. However, an assertion that forms the condition for a condi-
- tional subpattern may not be quantified. In practice, for other asser-
+ For compatibility with Perl, most assertion subpatterns may be
+ repeated; though it makes no sense to assert the same thing several
+ times, the side effect of capturing parentheses may occasionally be
+ useful. However, an assertion that forms the condition for a condi-
+ tional subpattern may not be quantified. In practice, for other asser-
tions, there only three cases:
- (1) If the quantifier is {0}, the assertion is never obeyed during
- matching. However, it may contain internal capturing parenthesized
+ (1) If the quantifier is {0}, the assertion is never obeyed during
+ matching. However, it may contain internal capturing parenthesized
groups that are called from elsewhere via the subroutine mechanism.
- (2) If quantifier is {0,n} where n is greater than zero, it is treated
- as if it were {0,1}. At run time, the rest of the pattern match is
+ (2) If quantifier is {0,n} where n is greater than zero, it is treated
+ as if it were {0,1}. At run time, the rest of the pattern match is
tried with and without the assertion, the order depending on the greed-
iness of the quantifier.
- (3) If the minimum repetition is greater than zero, the quantifier is
- ignored. The assertion is obeyed just once when encountered during
+ (3) If the minimum repetition is greater than zero, the quantifier is
+ ignored. The assertion is obeyed just once when encountered during
matching.
Lookahead assertions
@@ -8013,38 +8027,38 @@
\w+(?=;)
- matches a word followed by a semicolon, but does not include the semi-
+ matches a word followed by a semicolon, but does not include the semi-
colon in the match, and
foo(?!bar)
- matches any occurrence of "foo" that is not followed by "bar". Note
+ matches any occurrence of "foo" that is not followed by "bar". Note
that the apparently similar pattern
(?!foo)bar
- does not find an occurrence of "bar" that is preceded by something
- other than "foo"; it finds any occurrence of "bar" whatsoever, because
+ does not find an occurrence of "bar" that is preceded by something
+ other than "foo"; it finds any occurrence of "bar" whatsoever, because
the assertion (?!foo) is always true when the next three characters are
"bar". A lookbehind assertion is needed to achieve the other effect.
If you want to force a matching failure at some point in a pattern, the
- most convenient way to do it is with (?!) because an empty string
- always matches, so an assertion that requires there not to be an empty
+ most convenient way to do it is with (?!) because an empty string
+ always matches, so an assertion that requires there not to be an empty
string must always fail. The backtracking control verb (*FAIL) or (*F)
is a synonym for (?!).
Lookbehind assertions
- Lookbehind assertions start with (?<= for positive assertions and (?<!
+ Lookbehind assertions start with (?<= for positive assertions and (?<!
for negative assertions. For example,
(?<!foo)bar
- does find an occurrence of "bar" that is not preceded by "foo". The
- contents of a lookbehind assertion are restricted such that all the
+ does find an occurrence of "bar" that is not preceded by "foo". The
+ contents of a lookbehind assertion are restricted such that all the
strings it matches must have a fixed length. However, if there are sev-
- eral top-level alternatives, they do not all have to have the same
+ eral top-level alternatives, they do not all have to have the same
fixed length. Thus
(?<=bullock|donkey)
@@ -8053,66 +8067,66 @@
(?<!dogs?|cats?)
- causes an error at compile time. Branches that match different length
- strings are permitted only at the top level of a lookbehind assertion.
+ causes an error at compile time. Branches that match different length
+ strings are permitted only at the top level of a lookbehind assertion.
This is an extension compared with Perl, which requires all branches to
match the same length of string. An assertion such as
(?<=ab(c|de))
- is not permitted, because its single top-level branch can match two
- different lengths, but it is acceptable to PCRE2 if rewritten to use
+ is not permitted, because its single top-level branch can match two
+ different lengths, but it is acceptable to PCRE2 if rewritten to use
two top-level branches:
(?<=abc|abde)
- In some cases, the escape sequence \K (see above) can be used instead
+ In some cases, the escape sequence \K (see above) can be used instead
of a lookbehind assertion to get round the fixed-length restriction.
- The implementation of lookbehind assertions is, for each alternative,
- to temporarily move the current position back by the fixed length and
+ The implementation of lookbehind assertions is, for each alternative,
+ to temporarily move the current position back by the fixed length and
then try to match. If there are insufficient characters before the cur-
rent position, the assertion fails.
- In UTF-8 and UTF-16 modes, PCRE2 does not allow the \C escape (which
- matches a single code unit even in a UTF mode) to appear in lookbehind
- assertions, because it makes it impossible to calculate the length of
- the lookbehind. The \X and \R escapes, which can match different num-
+ In UTF-8 and UTF-16 modes, PCRE2 does not allow the \C escape (which
+ matches a single code unit even in a UTF mode) to appear in lookbehind
+ assertions, because it makes it impossible to calculate the length of
+ the lookbehind. The \X and \R escapes, which can match different num-
bers of code units, are never permitted in lookbehinds.
- "Subroutine" calls (see below) such as (?2) or (?&X) are permitted in
- lookbehinds, as long as the subpattern matches a fixed-length string.
- However, recursion, that is, a "subroutine" call into a group that is
+ "Subroutine" calls (see below) such as (?2) or (?&X) are permitted in
+ lookbehinds, as long as the subpattern matches a fixed-length string.
+ However, recursion, that is, a "subroutine" call into a group that is
already active, is not supported.
Perl does not support backreferences in lookbehinds. PCRE2 does support
- them, but only if certain conditions are met. The
- PCRE2_MATCH_UNSET_BACKREF option must not be set, there must be no use
+ them, but only if certain conditions are met. The
+ PCRE2_MATCH_UNSET_BACKREF option must not be set, there must be no use
of (?| in the pattern (it creates duplicate subpattern numbers), and if
- the backreference is by name, the name must be unique. Of course, the
- referenced subpattern must itself be of fixed length. The following
+ the backreference is by name, the name must be unique. Of course, the
+ referenced subpattern must itself be of fixed length. The following
pattern matches words containing at least two characters that begin and
end with the same character:
\b(\w)\w++(?<=\1)
- Possessive quantifiers can be used in conjunction with lookbehind
+ Possessive quantifiers can be used in conjunction with lookbehind
assertions to specify efficient matching of fixed-length strings at the
end of subject strings. Consider a simple pattern such as
abcd$
- when applied to a long string that does not match. Because matching
- proceeds from left to right, PCRE2 will look for each "a" in the sub-
- ject and then see if what follows matches the rest of the pattern. If
+ when applied to a long string that does not match. Because matching
+ proceeds from left to right, PCRE2 will look for each "a" in the sub-
+ ject and then see if what follows matches the rest of the pattern. If
the pattern is specified as
^.*abcd$
- the initial .* matches the entire string at first, but when this fails
+ the initial .* matches the entire string at first, but when this fails
(because there is no following "a"), it backtracks to match all but the
- last character, then all but the last two characters, and so on. Once
- again the search for "a" covers the entire string, from right to left,
+ last character, then all but the last two characters, and so on. Once
+ again the search for "a" covers the entire string, from right to left,
so we are no better off. However, if the pattern is written as
^.*+(?<=abcd)
@@ -8119,8 +8133,8 @@
there can be no backtracking for the .*+ item because of the possessive
quantifier; it can match only the entire string. The subsequent lookbe-
- hind assertion does a single test on the last four characters. If it
- fails, the match fails immediately. For long strings, this approach
+ hind assertion does a single test on the last four characters. If it
+ fails, the match fails immediately. For long strings, this approach
makes a significant difference to the processing time.
Using multiple assertions
@@ -8129,18 +8143,18 @@
(?<=\d{3})(?<!999)foo
- matches "foo" preceded by three digits that are not "999". Notice that
- each of the assertions is applied independently at the same point in
- the subject string. First there is a check that the previous three
- characters are all digits, and then there is a check that the same
+ matches "foo" preceded by three digits that are not "999". Notice that
+ each of the assertions is applied independently at the same point in
+ the subject string. First there is a check that the previous three
+ characters are all digits, and then there is a check that the same
three characters are not "999". This pattern does not match "foo" pre-
- ceded by six characters, the first of which are digits and the last
- three of which are not "999". For example, it doesn't match "123abc-
+ ceded by six characters, the first of which are digits and the last
+ three of which are not "999". For example, it doesn't match "123abc-
foo". A pattern to do that is
(?<=\d{3}...)(?<!999)foo
- This time the first assertion looks at the preceding six characters,
+ This time the first assertion looks at the preceding six characters,
checking that the first three are digits, and then the second assertion
checks that the preceding three characters are not "999".
@@ -8148,29 +8162,29 @@
(?<=(?<!foo)bar)baz
- matches an occurrence of "baz" that is preceded by "bar" which in turn
+ matches an occurrence of "baz" that is preceded by "bar" which in turn
is not preceded by "foo", while
(?<=\d{3}(?!999)...)foo
- is another pattern that matches "foo" preceded by three digits and any
+ is another pattern that matches "foo" preceded by three digits and any
three characters that are not "999".
CONDITIONAL SUBPATTERNS
- It is possible to cause the matching process to obey a subpattern con-
- ditionally or to choose between two alternative subpatterns, depending
- on the result of an assertion, or whether a specific capturing subpat-
- tern has already been matched. The two possible forms of conditional
+ It is possible to cause the matching process to obey a subpattern con-
+ ditionally or to choose between two alternative subpatterns, depending
+ on the result of an assertion, or whether a specific capturing subpat-
+ tern has already been matched. The two possible forms of conditional
subpattern are:
(?(condition)yes-pattern)
(?(condition)yes-pattern|no-pattern)
- If the condition is satisfied, the yes-pattern is used; otherwise the
- no-pattern (if present) is used. An absent no-pattern is equivalent to
- an empty string (it always matches). If there are more than two alter-
+ If the condition is satisfied, the yes-pattern is used; otherwise the
+ no-pattern (if present) is used. An absent no-pattern is equivalent to
+ an empty string (it always matches). If there are more than two alter-
natives in the subpattern, a compile-time error occurs. Each of the two
alternatives may itself contain nested subpatterns of any form, includ-
ing conditional subpatterns; the restriction to two alternatives
@@ -8180,57 +8194,57 @@
(?(1) (A|B|C) | (D | (?(2)E|F) | E) )
- There are five kinds of condition: references to subpatterns, refer-
- ences to recursion, two pseudo-conditions called DEFINE and VERSION,
+ There are five kinds of condition: references to subpatterns, refer-
+ ences to recursion, two pseudo-conditions called DEFINE and VERSION,
and assertions.
Checking for a used subpattern by number
- If the text between the parentheses consists of a sequence of digits,
+ If the text between the parentheses consists of a sequence of digits,
the condition is true if a capturing subpattern of that number has pre-
- viously matched. If there is more than one capturing subpattern with
- the same number (see the earlier section about duplicate subpattern
- numbers), the condition is true if any of them have matched. An alter-
- native notation is to precede the digits with a plus or minus sign. In
- this case, the subpattern number is relative rather than absolute. The
- most recently opened parentheses can be referenced by (?(-1), the next
- most recent by (?(-2), and so on. Inside loops it can also make sense
+ viously matched. If there is more than one capturing subpattern with
+ the same number (see the earlier section about duplicate subpattern
+ numbers), the condition is true if any of them have matched. An alter-
+ native notation is to precede the digits with a plus or minus sign. In
+ this case, the subpattern number is relative rather than absolute. The
+ most recently opened parentheses can be referenced by (?(-1), the next
+ most recent by (?(-2), and so on. Inside loops it can also make sense
to refer to subsequent groups. The next parentheses to be opened can be
- referenced as (?(+1), and so on. (The value zero in any of these forms
+ referenced as (?(+1), and so on. (The value zero in any of these forms
is not used; it provokes a compile-time error.)
- Consider the following pattern, which contains non-significant white
- space to make it more readable (assume the PCRE2_EXTENDED option) and
+ Consider the following pattern, which contains non-significant white
+ space to make it more readable (assume the PCRE2_EXTENDED option) and
to divide it into three parts for ease of discussion:
( \( )? [^()]+ (?(1) \) )
- The first part matches an optional opening parenthesis, and if that
+ The first part matches an optional opening parenthesis, and if that
character is present, sets it as the first captured substring. The sec-
- ond part matches one or more characters that are not parentheses. The
- third part is a conditional subpattern that tests whether or not the
- first set of parentheses matched. If they did, that is, if subject
- started with an opening parenthesis, the condition is true, and so the
- yes-pattern is executed and a closing parenthesis is required. Other-
- wise, since no-pattern is not present, the subpattern matches nothing.
- In other words, this pattern matches a sequence of non-parentheses,
+ ond part matches one or more characters that are not parentheses. The
+ third part is a conditional subpattern that tests whether or not the
+ first set of parentheses matched. If they did, that is, if subject
+ started with an opening parenthesis, the condition is true, and so the
+ yes-pattern is executed and a closing parenthesis is required. Other-
+ wise, since no-pattern is not present, the subpattern matches nothing.
+ In other words, this pattern matches a sequence of non-parentheses,
optionally enclosed in parentheses.
- If you were embedding this pattern in a larger one, you could use a
+ If you were embedding this pattern in a larger one, you could use a
relative reference:
...other stuff... ( \( )? [^()]+ (?(-1) \) ) ...
- This makes the fragment independent of the parentheses in the larger
+ This makes the fragment independent of the parentheses in the larger
pattern.
Checking for a used subpattern by name
- Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a
- used subpattern by name. For compatibility with earlier versions of
- PCRE1, which had this facility before Perl, the syntax (?(name)...) is
- also recognized. Note, however, that undelimited names consisting of
- the letter R followed by digits are ambiguous (see the following sec-
+ Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a
+ used subpattern by name. For compatibility with earlier versions of
+ PCRE1, which had this facility before Perl, the syntax (?(name)...) is
+ also recognized. Note, however, that undelimited names consisting of
+ the letter R followed by digits are ambiguous (see the following sec-
tion).
Rewriting the above example to use a named subpattern gives this:
@@ -8237,31 +8251,31 @@
(?<OPEN> \( )? [^()]+ (?(<OPEN>) \) )
- If the name used in a condition of this kind is a duplicate, the test
- is applied to all subpatterns of the same name, and is true if any one
+ If the name used in a condition of this kind is a duplicate, the test
+ is applied to all subpatterns of the same name, and is true if any one
of them has matched.
Checking for pattern recursion
- "Recursion" in this sense refers to any subroutine-like call from one
- part of the pattern to another, whether or not it is actually recur-
- sive. See the sections entitled "Recursive patterns" and "Subpatterns
+ "Recursion" in this sense refers to any subroutine-like call from one
+ part of the pattern to another, whether or not it is actually recur-
+ sive. See the sections entitled "Recursive patterns" and "Subpatterns
as subroutines" below for details of recursion and subpattern calls.
- If a condition is the string (R), and there is no subpattern with the
- name R, the condition is true if matching is currently in a recursion
- or subroutine call to the whole pattern or any subpattern. If digits
- follow the letter R, and there is no subpattern with that name, the
+ If a condition is the string (R), and there is no subpattern with the
+ name R, the condition is true if matching is currently in a recursion
+ or subroutine call to the whole pattern or any subpattern. If digits
+ follow the letter R, and there is no subpattern with that name, the
condition is true if the most recent call is into a subpattern with the
- given number, which must exist somewhere in the overall pattern. This
+ given number, which must exist somewhere in the overall pattern. This
is a contrived example that is equivalent to a+b:
((?(R1)a+|(?1)b))
- However, in both cases, if there is a subpattern with a matching name,
- the condition tests for its being set, as described in the section
- above, instead of testing for recursion. For example, creating a group
- with the name R1 by adding (?<R1>) to the above pattern completely
+ However, in both cases, if there is a subpattern with a matching name,
+ the condition tests for its being set, as described in the section
+ above, instead of testing for recursion. For example, creating a group
+ with the name R1 by adding (?<R1>) to the above pattern completely
changes its meaning.
If a name preceded by ampersand follows the letter R, for example:
@@ -8272,7 +8286,7 @@
of that name (which must exist within the pattern).
This condition does not check the entire recursion stack. It tests only
- the current level. If the name used in a condition of this kind is a
+ the current level. If the name used in a condition of this kind is a
duplicate, the test is applied to all subpatterns of the same name, and
is true if any one of them is the most recent recursion.
@@ -8281,10 +8295,10 @@
Defining subpatterns for use by reference only
If the condition is the string (DEFINE), the condition is always false,
- even if there is a group with the name DEFINE. In this case, there may
+ even if there is a group with the name DEFINE. In this case, there may
be only one alternative in the subpattern. It is always skipped if con-
- trol reaches this point in the pattern; the idea of DEFINE is that it
- can be used to define subroutines that can be referenced from else-
+ trol reaches this point in the pattern; the idea of DEFINE is that it
+ can be used to define subroutines that can be referenced from else-
where. (The use of subroutines is described below.) For example, a pat-
tern to match an IPv4 address such as "192.168.23.245" could be written
like this (ignore white space and line breaks):
@@ -8292,53 +8306,53 @@
(?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
\b (?&byte) (\.(?&byte)){3} \b
- The first part of the pattern is a DEFINE group inside which a another
- group named "byte" is defined. This matches an individual component of
- an IPv4 address (a number less than 256). When matching takes place,
- this part of the pattern is skipped because DEFINE acts like a false
- condition. The rest of the pattern uses references to the named group
- to match the four dot-separated components of an IPv4 address, insist-
+ The first part of the pattern is a DEFINE group inside which a another
+ group named "byte" is defined. This matches an individual component of
+ an IPv4 address (a number less than 256). When matching takes place,
+ this part of the pattern is skipped because DEFINE acts like a false
+ condition. The rest of the pattern uses references to the named group
+ to match the four dot-separated components of an IPv4 address, insist-
ing on a word boundary at each end.
Checking the PCRE2 version
- Programs that link with a PCRE2 library can check the version by call-
- ing pcre2_config() with appropriate arguments. Users of applications
- that do not have access to the underlying code cannot do this. A spe-
- cial "condition" called VERSION exists to allow such users to discover
+ Programs that link with a PCRE2 library can check the version by call-
+ ing pcre2_config() with appropriate arguments. Users of applications
+ that do not have access to the underlying code cannot do this. A spe-
+ cial "condition" called VERSION exists to allow such users to discover
which version of PCRE2 they are dealing with by using this condition to
- match a string such as "yesno". VERSION must be followed either by "="
+ match a string such as "yesno". VERSION must be followed either by "="
or ">=" and a version number. For example:
(?(VERSION>=10.4)yes|no)
- This pattern matches "yes" if the PCRE2 version is greater or equal to
- 10.4, or "no" otherwise. The fractional part of the version number may
+ This pattern matches "yes" if the PCRE2 version is greater or equal to
+ 10.4, or "no" otherwise. The fractional part of the version number may
not contain more than two digits.
Assertion conditions
- If the condition is not in any of the above formats, it must be an
- assertion. This may be a positive or negative lookahead or lookbehind
- assertion. Consider this pattern, again containing non-significant
+ If the condition is not in any of the above formats, it must be an
+ assertion. This may be a positive or negative lookahead or lookbehind
+ assertion. Consider this pattern, again containing non-significant
white space, and with the two alternatives on the second line:
(?(?=[^a-z]*[a-z])
\d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} )
- The condition is a positive lookahead assertion that matches an
- optional sequence of non-letters followed by a letter. In other words,
- it tests for the presence of at least one letter in the subject. If a
- letter is found, the subject is matched against the first alternative;
- otherwise it is matched against the second. This pattern matches
- strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are
+ The condition is a positive lookahead assertion that matches an
+ optional sequence of non-letters followed by a letter. In other words,
+ it tests for the presence of at least one letter in the subject. If a
+ letter is found, the subject is matched against the first alternative;
+ otherwise it is matched against the second. This pattern matches
+ strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are
letters and dd are digits.
- When an assertion that is a condition contains capturing subpatterns,
- any capturing that occurs in a matching branch is retained afterwards,
+ When an assertion that is a condition contains capturing subpatterns,
+ any capturing that occurs in a matching branch is retained afterwards,
for both positive and negative assertions, because matching always con-
tinues after the assertion, whether it succeeds or fails. (Compare non-
- conditional assertions, when captures are retained only for positive
+ conditional assertions, when captures are retained only for positive
assertions that succeed.)
@@ -8345,44 +8359,44 @@
COMMENTS
There are two ways of including comments in patterns that are processed
- by PCRE2. In both cases, the start of the comment must not be in a
- character class, nor in the middle of any other sequence of related
- characters such as (?: or a subpattern name or number. The characters
+ by PCRE2. In both cases, the start of the comment must not be in a
+ character class, nor in the middle of any other sequence of related
+ characters such as (?: or a subpattern name or number. The characters
that make up a comment play no part in the pattern matching.
- The sequence (?# marks the start of a comment that continues up to the
- next closing parenthesis. Nested parentheses are not permitted. If the
- PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, an unescaped #
- character also introduces a comment, which in this case continues to
- immediately after the next newline character or character sequence in
+ The sequence (?# marks the start of a comment that continues up to the
+ next closing parenthesis. Nested parentheses are not permitted. If the
+ PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, an unescaped #
+ character also introduces a comment, which in this case continues to
+ immediately after the next newline character or character sequence in
the pattern. Which characters are interpreted as newlines is controlled
- by an option passed to the compiling function or by a special sequence
+ by an option passed to the compiling function or by a special sequence
at the start of the pattern, as described in the section entitled "New-
line conventions" above. Note that the end of this type of comment is a
- literal newline sequence in the pattern; escape sequences that happen
+ literal newline sequence in the pattern; escape sequences that happen
to represent a newline do not count. For example, consider this pattern
- when PCRE2_EXTENDED is set, and the default newline convention (a sin-
+ when PCRE2_EXTENDED is set, and the default newline convention (a sin-
gle linefeed character) is in force:
abc #comment \n still comment
- On encountering the # character, pcre2_compile() skips along, looking
- for a newline in the pattern. The sequence \n is still literal at this
- stage, so it does not terminate the comment. Only an actual character
+ On encountering the # character, pcre2_compile() skips along, looking
+ for a newline in the pattern. The sequence \n is still literal at this
+ stage, so it does not terminate the comment. Only an actual character
with the code value 0x0a (the default newline) does so.
RECURSIVE PATTERNS
- Consider the problem of matching a string in parentheses, allowing for
- unlimited nested parentheses. Without the use of recursion, the best
- that can be done is to use a pattern that matches up to some fixed
- depth of nesting. It is not possible to handle an arbitrary nesting
+ Consider the problem of matching a string in parentheses, allowing for
+ unlimited nested parentheses. Without the use of recursion, the best
+ that can be done is to use a pattern that matches up to some fixed
+ depth of nesting. It is not possible to handle an arbitrary nesting
depth.
For some time, Perl has provided a facility that allows regular expres-
- sions to recurse (amongst other things). It does this by interpolating
- Perl code in the expression at run time, and the code can refer to the
+ sions to recurse (amongst other things). It does this by interpolating
+ Perl code in the expression at run time, and the code can refer to the
expression itself. A Perl pattern using code interpolation to solve the
parentheses problem can be created like this:
@@ -8392,109 +8406,109 @@
refers recursively to the pattern in which it appears.
Obviously, PCRE2 cannot support the interpolation of Perl code.
- Instead, it supports special syntax for recursion of the entire pat-
+ Instead, it supports special syntax for recursion of the entire pat-
tern, and also for individual subpattern recursion. After its introduc-
- tion in PCRE1 and Python, this kind of recursion was subsequently
+ tion in PCRE1 and Python, this kind of recursion was subsequently
introduced into Perl at release 5.10.
- A special item that consists of (? followed by a number greater than
- zero and a closing parenthesis is a recursive subroutine call of the
- subpattern of the given number, provided that it occurs inside that
- subpattern. (If not, it is a non-recursive subroutine call, which is
- described in the next section.) The special item (?R) or (?0) is a
+ A special item that consists of (? followed by a number greater than
+ zero and a closing parenthesis is a recursive subroutine call of the
+ subpattern of the given number, provided that it occurs inside that
+ subpattern. (If not, it is a non-recursive subroutine call, which is
+ described in the next section.) The special item (?R) or (?0) is a
recursive call of the entire regular expression.
- This PCRE2 pattern solves the nested parentheses problem (assume the
+ This PCRE2 pattern solves the nested parentheses problem (assume the
PCRE2_EXTENDED option is set so that white space is ignored):
\( ( [^()]++ | (?R) )* \)
- First it matches an opening parenthesis. Then it matches any number of
- substrings which can either be a sequence of non-parentheses, or a
- recursive match of the pattern itself (that is, a correctly parenthe-
+ First it matches an opening parenthesis. Then it matches any number of
+ substrings which can either be a sequence of non-parentheses, or a
+ recursive match of the pattern itself (that is, a correctly parenthe-
sized substring). Finally there is a closing parenthesis. Note the use
of a possessive quantifier to avoid backtracking into sequences of non-
parentheses.
- If this were part of a larger pattern, you would not want to recurse
+ If this were part of a larger pattern, you would not want to recurse
the entire pattern, so instead you could use this:
( \( ( [^()]++ | (?1) )* \) )
- We have put the pattern into parentheses, and caused the recursion to
+ We have put the pattern into parentheses, and caused the recursion to
refer to them instead of the whole pattern.
- In a larger pattern, keeping track of parenthesis numbers can be
- tricky. This is made easier by the use of relative references. Instead
+ In a larger pattern, keeping track of parenthesis numbers can be
+ tricky. This is made easier by the use of relative references. Instead
of (?1) in the pattern above you can write (?-2) to refer to the second
- most recently opened parentheses preceding the recursion. In other
- words, a negative number counts capturing parentheses leftwards from
+ most recently opened parentheses preceding the recursion. In other
+ words, a negative number counts capturing parentheses leftwards from
the point at which it is encountered.
Be aware however, that if duplicate subpattern numbers are in use, rel-
- ative references refer to the earliest subpattern with the appropriate
+ ative references refer to the earliest subpattern with the appropriate
number. Consider, for example:
(?|(a)|(b)) (c) (?-2)
- The first two capturing groups (a) and (b) are both numbered 1, and
- group (c) is number 2. When the reference (?-2) is encountered, the
+ The first two capturing groups (a) and (b) are both numbered 1, and
+ group (c) is number 2. When the reference (?-2) is encountered, the
second most recently opened parentheses has the number 1, but it is the
- first such group (the (a) group) to which the recursion refers. This
- would be the same if an absolute reference (?1) was used. In other
- words, relative references are just a shorthand for computing a group
+ first such group (the (a) group) to which the recursion refers. This
+ would be the same if an absolute reference (?1) was used. In other
+ words, relative references are just a shorthand for computing a group
number.
- It is also possible to refer to subsequently opened parentheses, by
- writing references such as (?+2). However, these cannot be recursive
- because the reference is not inside the parentheses that are refer-
- enced. They are always non-recursive subroutine calls, as described in
+ It is also possible to refer to subsequently opened parentheses, by
+ writing references such as (?+2). However, these cannot be recursive
+ because the reference is not inside the parentheses that are refer-
+ enced. They are always non-recursive subroutine calls, as described in
the next section.
- An alternative approach is to use named parentheses. The Perl syntax
- for this is (?&name); PCRE1's earlier syntax (?P>name) is also sup-
+ An alternative approach is to use named parentheses. The Perl syntax
+ for this is (?&name); PCRE1's earlier syntax (?P>name) is also sup-
ported. We could rewrite the above example as follows:
(?<pn> \( ( [^()]++ | (?&pn) )* \) )
- If there is more than one subpattern with the same name, the earliest
+ If there is more than one subpattern with the same name, the earliest
one is used.
The example pattern that we have been looking at contains nested unlim-
- ited repeats, and so the use of a possessive quantifier for matching
- strings of non-parentheses is important when applying the pattern to
+ ited repeats, and so the use of a possessive quantifier for matching
+ strings of non-parentheses is important when applying the pattern to
strings that do not match. For example, when this pattern is applied to
(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
- it yields "no match" quickly. However, if a possessive quantifier is
- not used, the match runs for a very long time indeed because there are
- so many different ways the + and * repeats can carve up the subject,
+ it yields "no match" quickly. However, if a possessive quantifier is
+ not used, the match runs for a very long time indeed because there are
+ so many different ways the + and * repeats can carve up the subject,
and all have to be tested before failure can be reported.
- At the end of a match, the values of capturing parentheses are those
- from the outermost level. If you want to obtain intermediate values, a
+ At the end of a match, the values of capturing parentheses are those
+ from the outermost level. If you want to obtain intermediate values, a
callout function can be used (see below and the pcre2callout documenta-
tion). If the pattern above is matched against
(ab(cd)ef)
- the value for the inner capturing parentheses (numbered 2) is "ef",
- which is the last value taken on at the top level. If a capturing sub-
- pattern is not matched at the top level, its final captured value is
- unset, even if it was (temporarily) set at a deeper level during the
+ the value for the inner capturing parentheses (numbered 2) is "ef",
+ which is the last value taken on at the top level. If a capturing sub-
+ pattern is not matched at the top level, its final captured value is
+ unset, even if it was (temporarily) set at a deeper level during the
matching process.
- Do not confuse the (?R) item with the condition (R), which tests for
- recursion. Consider this pattern, which matches text in angle brack-
- ets, allowing for arbitrary nesting. Only digits are allowed in nested
- brackets (that is, when recursing), whereas any characters are permit-
+ Do not confuse the (?R) item with the condition (R), which tests for
+ recursion. Consider this pattern, which matches text in angle brack-
+ ets, allowing for arbitrary nesting. Only digits are allowed in nested
+ brackets (that is, when recursing), whereas any characters are permit-
ted at the outer level.
< (?: (?(R) \d++ | [^<>]*+) | (?R)) * >
- In this pattern, (?(R) is the start of a conditional subpattern, with
- two different alternatives for the recursive and non-recursive cases.
+ In this pattern, (?(R) is the start of a conditional subpattern, with
+ two different alternatives for the recursive and non-recursive cases.
The (?R) item is the actual recursive call.
Differences in recursion processing between PCRE2 and Perl
@@ -8501,66 +8515,66 @@
Some former differences between PCRE2 and Perl no longer exist.
- Before release 10.30, recursion processing in PCRE2 differed from Perl
- in that a recursive subpattern call was always treated as an atomic
- group. That is, once it had matched some of the subject string, it was
- never re-entered, even if it contained untried alternatives and there
- was a subsequent matching failure. (Historical note: PCRE implemented
+ Before release 10.30, recursion processing in PCRE2 differed from Perl
+ in that a recursive subpattern call was always treated as an atomic
+ group. That is, once it had matched some of the subject string, it was
+ never re-entered, even if it contained untried alternatives and there
+ was a subsequent matching failure. (Historical note: PCRE implemented
recursion before Perl did.)
- Starting with release 10.30, recursive subroutine calls are no longer
+ Starting with release 10.30, recursive subroutine calls are no longer
treated as atomic. That is, they can be re-entered to try unused alter-
- natives if there is a matching failure later in the pattern. This is
- now compatible with the way Perl works. If you want a subroutine call
+ natives if there is a matching failure later in the pattern. This is
+ now compatible with the way Perl works. If you want a subroutine call
to be atomic, you must explicitly enclose it in an atomic group.
- Supporting backtracking into recursions simplifies certain types of
+ Supporting backtracking into recursions simplifies certain types of
recursive pattern. For example, this pattern matches palindromic
strings:
^((.)(?1)\2|.?)$
- The second branch in the group matches a single central character in
- the palindrome when there are an odd number of characters, or nothing
- when there are an even number of characters, but in order to work it
- has to be able to try the second case when the rest of the pattern
+ The second branch in the group matches a single central character in
+ the palindrome when there are an odd number of characters, or nothing
+ when there are an even number of characters, but in order to work it
+ has to be able to try the second case when the rest of the pattern
match fails. If you want to match typical palindromic phrases, the pat-
- tern has to ignore all non-word characters, which can be done like
+ tern has to ignore all non-word characters, which can be done like
this:
^\W*+((.)\W*+(?1)\W*+\2|\W*+.?)\W*+$
- If run with the PCRE2_CASELESS option, this pattern matches phrases
- such as "A man, a plan, a canal: Panama!". Note the use of the posses-
- sive quantifier *+ to avoid backtracking into sequences of non-word
+ If run with the PCRE2_CASELESS option, this pattern matches phrases
+ such as "A man, a plan, a canal: Panama!". Note the use of the posses-
+ sive quantifier *+ to avoid backtracking into sequences of non-word
characters. Without this, PCRE2 takes a great deal longer (ten times or
- more) to match typical phrases, and Perl takes so long that you think
+ more) to match typical phrases, and Perl takes so long that you think
it has gone into a loop.
- Another way in which PCRE2 and Perl used to differ in their recursion
- processing is in the handling of captured values. Formerly in Perl,
- when a subpattern was called recursively or as a subpattern (see the
- next section), it had no access to any values that were captured out-
- side the recursion, whereas in PCRE2 these values can be referenced.
+ Another way in which PCRE2 and Perl used to differ in their recursion
+ processing is in the handling of captured values. Formerly in Perl,
+ when a subpattern was called recursively or as a subpattern (see the
+ next section), it had no access to any values that were captured out-
+ side the recursion, whereas in PCRE2 these values can be referenced.
Consider this pattern:
^(.)(\1|a(?2))
- This pattern matches "bab". The first capturing parentheses match "b",
+ This pattern matches "bab". The first capturing parentheses match "b",
then in the second group, when the backreference \1 fails to match "b",
the second alternative matches "a" and then recurses. In the recursion,
- \1 does now match "b" and so the whole match succeeds. This match used
+ \1 does now match "b" and so the whole match succeeds. This match used
to fail in Perl, but in later versions (I tried 5.024) it now works.
SUBPATTERNS AS SUBROUTINES
- If the syntax for a recursive subpattern call (either by number or by
+ If the syntax for a recursive subpattern call (either by number or by
name) is used outside the parentheses to which it refers, it operates a
bit like a subroutine in a programming language. More accurately, PCRE2
- treats the referenced subpattern as an independent subpattern which it
- tries to match at the current matching position. The called subpattern
- may be defined before or after the reference. A numbered reference can
+ treats the referenced subpattern as an independent subpattern which it
+ tries to match at the current matching position. The called subpattern
+ may be defined before or after the reference. A numbered reference can
be absolute or relative, as in these examples:
(...(absolute)...)...(?2)...
@@ -8571,30 +8585,30 @@
(sens|respons)e and \1ibility
- matches "sense and sensibility" and "response and responsibility", but
+ matches "sense and sensibility" and "response and responsibility", but
not "sense and responsibility". If instead the pattern
(sens|respons)e and (?1)ibility
- is used, it does match "sense and responsibility" as well as the other
- two strings. Another example is given in the discussion of DEFINE
+ is used, it does match "sense and responsibility" as well as the other
+ two strings. Another example is given in the discussion of DEFINE
above.
- Like recursions, subroutine calls used to be treated as atomic, but
- this changed at PCRE2 release 10.30, so backtracking into subroutine
- calls can now occur. However, any capturing parentheses that are set
+ Like recursions, subroutine calls used to be treated as atomic, but
+ this changed at PCRE2 release 10.30, so backtracking into subroutine
+ calls can now occur. However, any capturing parentheses that are set
during the subroutine call revert to their previous values afterwards.
- Processing options such as case-independence are fixed when a subpat-
- tern is defined, so if it is used as a subroutine, such options cannot
+ Processing options such as case-independence are fixed when a subpat-
+ tern is defined, so if it is used as a subroutine, such options cannot
be changed for different calls. For example, consider this pattern:
(abc)(?i:(?-1))
- It matches "abcabc". It does not match "abcABC" because the change of
+ It matches "abcabc". It does not match "abcABC" because the change of
processing option does not affect the called subpattern.
- The behaviour of backtracking control verbs in subpatterns when called
+ The behaviour of backtracking control verbs in subpatterns when called
as subroutines is described in the section entitled "Backtracking verbs
in subroutines" below.
@@ -8601,22 +8615,22 @@
ONIGURUMA SUBROUTINE SYNTAX
- For compatibility with Oniguruma, the non-Perl syntax \g followed by a
+ For compatibility with Oniguruma, the non-Perl syntax \g followed by a
name or a number enclosed either in angle brackets or single quotes, is
- an alternative syntax for referencing a subpattern as a subroutine,
- possibly recursively. Here are two of the examples used above, rewrit-
+ an alternative syntax for referencing a subpattern as a subroutine,
+ possibly recursively. Here are two of the examples used above, rewrit-
ten using this syntax:
(?<pn> \( ( (?>[^()]+) | \g<pn> )* \) )
(sens|respons)e and \g'1'ibility
- PCRE2 supports an extension to Oniguruma: if a number is preceded by a
+ PCRE2 supports an extension to Oniguruma: if a number is preceded by a
plus or a minus sign it is taken as a relative reference. For example:
(abc)(?i:\g<-1>)
- Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not
- synonymous. The former is a backreference; the latter is a subroutine
+ Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not
+ synonymous. The former is a backreference; the latter is a subroutine
call.
@@ -8623,54 +8637,54 @@
CALLOUTS
Perl has a feature whereby using the sequence (?{...}) causes arbitrary
- Perl code to be obeyed in the middle of matching a regular expression.
+ Perl code to be obeyed in the middle of matching a regular expression.
This makes it possible, amongst other things, to extract different sub-
strings that match the same pair of parentheses when there is a repeti-
tion.
- PCRE2 provides a similar feature, but of course it cannot obey arbi-
- trary Perl code. The feature is called "callout". The caller of PCRE2
- provides an external function by putting its entry point in a match
- context using the function pcre2_set_callout(), and then passing that
- context to pcre2_match() or pcre2_dfa_match(). If no match context is
+ PCRE2 provides a similar feature, but of course it cannot obey arbi-
+ trary Perl code. The feature is called "callout". The caller of PCRE2
+ provides an external function by putting its entry point in a match
+ context using the function pcre2_set_callout(), and then passing that
+ context to pcre2_match() or pcre2_dfa_match(). If no match context is
passed, or if the callout entry point is set to NULL, callouts are dis-
abled.
- Within a regular expression, (?C<arg>) indicates a point at which the
- external function is to be called. There are two kinds of callout:
- those with a numerical argument and those with a string argument. (?C)
- on its own with no argument is treated as (?C0). A numerical argument
- allows the application to distinguish between different callouts.
- String arguments were added for release 10.20 to make it possible for
- script languages that use PCRE2 to embed short scripts within patterns
+ Within a regular expression, (?C<arg>) indicates a point at which the
+ external function is to be called. There are two kinds of callout:
+ those with a numerical argument and those with a string argument. (?C)
+ on its own with no argument is treated as (?C0). A numerical argument
+ allows the application to distinguish between different callouts.
+ String arguments were added for release 10.20 to make it possible for
+ script languages that use PCRE2 to embed short scripts within patterns
in a similar way to Perl.
During matching, when PCRE2 reaches a callout point, the external func-
- tion is called. It is provided with the number or string argument of
- the callout, the position in the pattern, and one item of data that is
+ tion is called. It is provided with the number or string argument of
+ the callout, the position in the pattern, and one item of data that is
also set in the match block. The callout function may cause matching to
proceed, to backtrack, or to fail.
- By default, PCRE2 implements a number of optimizations at matching
- time, and one side-effect is that sometimes callouts are skipped. If
- you need all possible callouts to happen, you need to set options that
- disable the relevant optimizations. More details, including a complete
- description of the programming interface to the callout function, are
+ By default, PCRE2 implements a number of optimizations at matching
+ time, and one side-effect is that sometimes callouts are skipped. If
+ you need all possible callouts to happen, you need to set options that
+ disable the relevant optimizations. More details, including a complete
+ description of the programming interface to the callout function, are
given in the pcre2callout documentation.
Callouts with numerical arguments
- If you just want to have a means of identifying different callout
- points, put a number less than 256 after the letter C. For example,
+ If you just want to have a means of identifying different callout
+ points, put a number less than 256 after the letter C. For example,
this pattern has two callout points:
(?C1)abc(?C2)def
- If the PCRE2_AUTO_CALLOUT flag is passed to pcre2_compile(), numerical
- callouts are automatically installed before each item in the pattern.
- They are all numbered 255. If there is a conditional group in the pat-
+ If the PCRE2_AUTO_CALLOUT flag is passed to pcre2_compile(), numerical
+ callouts are automatically installed before each item in the pattern.
+ They are all numbered 255. If there is a conditional group in the pat-
tern whose condition is an assertion, an additional callout is inserted
- just before the condition. An explicit callout may also be set at this
+ just before the condition. An explicit callout may also be set at this
position, as in this example:
(?(?C9)(?=a)abc|def)
@@ -8680,60 +8694,60 @@
Callouts with string arguments
- A delimited string may be used instead of a number as a callout argu-
- ment. The starting delimiter must be one of ` ' " ^ % # $ { and the
+ A delimited string may be used instead of a number as a callout argu-
+ ment. The starting delimiter must be one of ` ' " ^ % # $ { and the
ending delimiter is the same as the start, except for {, where the end-
- ing delimiter is }. If the ending delimiter is needed within the
+ ing delimiter is }. If the ending delimiter is needed within the
string, it must be doubled. For example:
(?C'ab ''c'' d')xyz(?C{any text})pqr
- The doubling is removed before the string is passed to the callout
+ The doubling is removed before the string is passed to the callout
function.
BACKTRACKING CONTROL
- There are a number of special "Backtracking Control Verbs" (to use
- Perl's terminology) that modify the behaviour of backtracking during
- matching. They are generally of the form (*VERB) or (*VERB:NAME). Some
- verbs take either form, possibly behaving differently depending on
+ There are a number of special "Backtracking Control Verbs" (to use
+ Perl's terminology) that modify the behaviour of backtracking during
+ matching. They are generally of the form (*VERB) or (*VERB:NAME). Some
+ verbs take either form, possibly behaving differently depending on
whether or not a name is present.
- By default, for compatibility with Perl, a name is any sequence of
+ By default, for compatibility with Perl, a name is any sequence of
characters that does not include a closing parenthesis. The name is not
- processed in any way, and it is not possible to include a closing
- parenthesis in the name. This can be changed by setting the
- PCRE2_ALT_VERBNAMES option, but the result is no longer Perl-compati-
+ processed in any way, and it is not possible to include a closing
+ parenthesis in the name. This can be changed by setting the
+ PCRE2_ALT_VERBNAMES option, but the result is no longer Perl-compati-
ble.
- When PCRE2_ALT_VERBNAMES is set, backslash processing is applied to
- verb names and only an unescaped closing parenthesis terminates the
- name. However, the only backslash items that are permitted are \Q, \E,
- and sequences such as \x{100} that define character code points. Char-
+ When PCRE2_ALT_VERBNAMES is set, backslash processing is applied to
+ verb names and only an unescaped closing parenthesis terminates the
+ name. However, the only backslash items that are permitted are \Q, \E,
+ and sequences such as \x{100} that define character code points. Char-
acter type escapes such as \d are faulted.
A closing parenthesis can be included in a name either as \) or between
- \Q and \E. In addition to backslash processing, if the PCRE2_EXTENDED
+ \Q and \E. In addition to backslash processing, if the PCRE2_EXTENDED
or PCRE2_EXTENDED_MORE option is also set, unescaped whitespace in verb
names is skipped, and #-comments are recognized, exactly as in the rest
- of the pattern. PCRE2_EXTENDED and PCRE2_EXTENDED_MORE do not affect
+ of the pattern. PCRE2_EXTENDED and PCRE2_EXTENDED_MORE do not affect
verb names unless PCRE2_ALT_VERBNAMES is also set.
- The maximum length of a name is 255 in the 8-bit library and 65535 in
- the 16-bit and 32-bit libraries. If the name is empty, that is, if the
- closing parenthesis immediately follows the colon, the effect is as if
+ The maximum length of a name is 255 in the 8-bit library and 65535 in
+ the 16-bit and 32-bit libraries. If the name is empty, that is, if the
+ closing parenthesis immediately follows the colon, the effect is as if
the colon were not there. Any number of these verbs may occur in a pat-
tern.
- Since these verbs are specifically related to backtracking, most of
- them can be used only when the pattern is to be matched using the tra-
+ Since these verbs are specifically related to backtracking, most of
+ them can be used only when the pattern is to be matched using the tra-
ditional matching function, because that uses a backtracking algorithm.
- With the exception of (*FAIL), which behaves like a failing negative
+ With the exception of (*FAIL), which behaves like a failing negative
assertion, the backtracking control verbs cause an error if encountered
by the DFA matching function.
- The behaviour of these verbs in repeated groups, assertions, and in
+ The behaviour of these verbs in repeated groups, assertions, and in
subpatterns called as subroutines (whether or not recursively) is docu-
mented below.
@@ -8741,16 +8755,16 @@
PCRE2 contains some optimizations that are used to speed up matching by
running some checks at the start of each match attempt. For example, it
- may know the minimum length of matching subject, or that a particular
+ may know the minimum length of matching subject, or that a particular
character must be present. When one of these optimizations bypasses the
- running of a match, any included backtracking verbs will not, of
+ running of a match, any included backtracking verbs will not, of
course, be processed. You can suppress the start-of-match optimizations
- by setting the PCRE2_NO_START_OPTIMIZE option when calling pcre2_com-
- pile(), or by starting the pattern with (*NO_START_OPT). There is more
+ by setting the PCRE2_NO_START_OPTIMIZE option when calling pcre2_com-
+ pile(), or by starting the pattern with (*NO_START_OPT). There is more
discussion of this option in the section entitled "Compiling a pattern"
in the pcre2api documentation.
- Experiments with Perl suggest that it too has similar optimizations,
+ Experiments with Perl suggest that it too has similar optimizations,
and like PCRE2, turning them off can change the result of a match.
Verbs that act immediately
@@ -8759,63 +8773,63 @@
(*ACCEPT) or (*ACCEPT:NAME)
- This verb causes the match to end successfully, skipping the remainder
- of the pattern. However, when it is inside a subpattern that is called
- as a subroutine, only that subpattern is ended successfully. Matching
+ This verb causes the match to end successfully, skipping the remainder
+ of the pattern. However, when it is inside a subpattern that is called
+ as a subroutine, only that subpattern is ended successfully. Matching
then continues at the outer level. If (*ACCEPT) in triggered in a posi-
- tive assertion, the assertion succeeds; in a negative assertion, the
+ tive assertion, the assertion succeeds; in a negative assertion, the
assertion fails.
- If (*ACCEPT) is inside capturing parentheses, the data so far is cap-
+ If (*ACCEPT) is inside capturing parentheses, the data so far is cap-
tured. For example:
A((?:A|B(*ACCEPT)|C)D)
- This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
+ This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
tured by the outer parentheses.
(*FAIL) or (*FAIL:NAME)
- This verb causes a matching failure, forcing backtracking to occur. It
- may be abbreviated to (*F). It is equivalent to (?!) but easier to
+ This verb causes a matching failure, forcing backtracking to occur. It
+ may be abbreviated to (*F). It is equivalent to (?!) but easier to
read. The Perl documentation notes that it is probably useful only when
combined with (?{}) or (??{}). Those are, of course, Perl features that
- are not present in PCRE2. The nearest equivalent is the callout fea-
+ are not present in PCRE2. The nearest equivalent is the callout fea-
ture, as for example in this pattern:
a+(?C)(*FAIL)
- A match with the string "aaaa" always fails, but the callout is taken
+ A match with the string "aaaa" always fails, but the callout is taken
before each backtrack happens (in this example, 10 times).
- (*ACCEPT:NAME) and (*FAIL:NAME) behave exactly the same as
+ (*ACCEPT:NAME) and (*FAIL:NAME) behave exactly the same as
(*MARK:NAME)(*ACCEPT) and (*MARK:NAME)(*FAIL), respectively.
Recording which path was taken
- There is one verb whose main purpose is to track how a match was
- arrived at, though it also has a secondary use in conjunction with
+ There is one verb whose main purpose is to track how a match was
+ arrived at, though it also has a secondary use in conjunction with
advancing the match starting point (see (*SKIP) below).
(*MARK:NAME) or (*:NAME)
- A name is always required with this verb. There may be as many
- instances of (*MARK) as you like in a pattern, and their names do not
+ A name is always required with this verb. There may be as many
+ instances of (*MARK) as you like in a pattern, and their names do not
have to be unique.
When a match succeeds, the name of the last-encountered (*MARK:NAME) on
the matching path is passed back to the caller as described in the sec-
tion entitled "Other information about the match" in the pcre2api docu-
- mentation. This applies to all instances of (*MARK), including those
- inside assertions and atomic groups. (There are differences in those
- cases when (*MARK) is used in conjunction with (*SKIP) as described
+ mentation. This applies to all instances of (*MARK), including those
+ inside assertions and atomic groups. (There are differences in those
+ cases when (*MARK) is used in conjunction with (*SKIP) as described
below.)
- As well as (*MARK), the (*COMMIT), (*PRUNE) and (*THEN) verbs may have
- associated NAME arguments. Whichever is last on the matching path is
+ As well as (*MARK), the (*COMMIT), (*PRUNE) and (*THEN) verbs may have
+ associated NAME arguments. Whichever is last on the matching path is
passed back. See below for more details of these other verbs.
- Here is an example of pcre2test output, where the "mark" modifier
+ Here is an example of pcre2test output, where the "mark" modifier
requests the retrieval and outputting of (*MARK) data:
re> /X(*MARK:A)Y|X(*MARK:B)Z/mark
@@ -8827,16 +8841,16 @@
MK: B
The (*MARK) name is tagged with "MK:" in this output, and in this exam-
- ple it indicates which of the two alternatives matched. This is a more
- efficient way of obtaining this information than putting each alterna-
+ ple it indicates which of the two alternatives matched. This is a more
+ efficient way of obtaining this information than putting each alterna-
tive in its own capturing parentheses.
- If a verb with a name is encountered in a positive assertion that is
- true, the name is recorded and passed back if it is the last-encoun-
+ If a verb with a name is encountered in a positive assertion that is
+ true, the name is recorded and passed back if it is the last-encoun-
tered. This does not happen for negative assertions or failing positive
assertions.
- After a partial match or a failed match, the last encountered name in
+ After a partial match or a failed match, the last encountered name in
the entire match process is returned. For example:
re> /X(*MARK:A)Y|X(*MARK:B)Z/mark
@@ -8843,38 +8857,38 @@
data> XP
No match, mark = B
- Note that in this unanchored example the mark is retained from the
+ Note that in this unanchored example the mark is retained from the
match attempt that started at the letter "X" in the subject. Subsequent
match attempts starting at "P" and then with an empty string do not get
as far as the (*MARK) item, but nevertheless do not reset it.
- If you are interested in (*MARK) values after failed matches, you
- should probably set the PCRE2_NO_START_OPTIMIZE option (see above) to
+ If you are interested in (*MARK) values after failed matches, you
+ should probably set the PCRE2_NO_START_OPTIMIZE option (see above) to
ensure that the match is always attempted.
Verbs that act after backtracking
The following verbs do nothing when they are encountered. Matching con-
- tinues with what follows, but if there is a subsequent match failure,
- causing a backtrack to the verb, a failure is forced. That is, back-
- tracking cannot pass to the left of the verb. However, when one of
+ tinues with what follows, but if there is a subsequent match failure,
+ causing a backtrack to the verb, a failure is forced. That is, back-
+ tracking cannot pass to the left of the verb. However, when one of
these verbs appears inside an atomic group or in a lookaround assertion
- that is true, its effect is confined to that group, because once the
- group has been matched, there is never any backtracking into it. Back-
+ that is true, its effect is confined to that group, because once the
+ group has been matched, there is never any backtracking into it. Back-
tracking from beyond an assertion or an atomic group ignores the entire
group, and seeks a preceeding backtracking point.
- These verbs differ in exactly what kind of failure occurs when back-
- tracking reaches them. The behaviour described below is what happens
- when the verb is not in a subroutine or an assertion. Subsequent sec-
+ These verbs differ in exactly what kind of failure occurs when back-
+ tracking reaches them. The behaviour described below is what happens
+ when the verb is not in a subroutine or an assertion. Subsequent sec-
tions cover these special cases.
(*COMMIT) or (*COMMIT:NAME)
- This verb causes the whole match to fail outright if there is a later
+ This verb causes the whole match to fail outright if there is a later
matching failure that causes backtracking to reach it. Even if the pat-
- tern is unanchored, no further attempts to find a match by advancing
- the starting point take place. If (*COMMIT) is the only backtracking
+ tern is unanchored, no further attempts to find a match by advancing
+ the starting point take place. If (*COMMIT) is the only backtracking
verb that is encountered, once it has been passed pcre2_match() is com-
mitted to finding a match at the current starting point, or not at all.
For example:
@@ -8881,22 +8895,22 @@
a+(*COMMIT)b
- This matches "xxaab" but not "aacaab". It can be thought of as a kind
+ This matches "xxaab" but not "aacaab". It can be thought of as a kind
of dynamic anchor, or "I've started, so I must finish."
- The behaviour of (*COMMIT:NAME) is not the same as (*MARK:NAME)(*COM-
- MIT). It is like (*MARK:NAME) in that the name is remembered for pass-
- ing back to the caller. However, (*SKIP:NAME) searches only for names
- set with (*MARK), ignoring those set by (*COMMIT), (*PRUNE) and
+ The behaviour of (*COMMIT:NAME) is not the same as (*MARK:NAME)(*COM-
+ MIT). It is like (*MARK:NAME) in that the name is remembered for pass-
+ ing back to the caller. However, (*SKIP:NAME) searches only for names
+ set with (*MARK), ignoring those set by (*COMMIT), (*PRUNE) and
(*THEN).
- If there is more than one backtracking verb in a pattern, a different
- one that follows (*COMMIT) may be triggered first, so merely passing
+ If there is more than one backtracking verb in a pattern, a different
+ one that follows (*COMMIT) may be triggered first, so merely passing
(*COMMIT) during a match does not always guarantee that a match must be
at this starting point.
- Note that (*COMMIT) at the start of a pattern is not the same as an
- anchor, unless PCRE2's start-of-match optimizations are turned off, as
+ Note that (*COMMIT) at the start of a pattern is not the same as an
+ anchor, unless PCRE2's start-of-match optimizations are turned off, as
shown in this output from pcre2test:
re> /(*COMMIT)abc/
@@ -8907,63 +8921,63 @@
data> xyzabc
No match
- For the first pattern, PCRE2 knows that any match must start with "a",
- so the optimization skips along the subject to "a" before applying the
- pattern to the first set of data. The match attempt then succeeds. The
- second pattern disables the optimization that skips along to the first
- character. The pattern is now applied starting at "x", and so the
- (*COMMIT) causes the match to fail without trying any other starting
+ For the first pattern, PCRE2 knows that any match must start with "a",
+ so the optimization skips along the subject to "a" before applying the
+ pattern to the first set of data. The match attempt then succeeds. The
+ second pattern disables the optimization that skips along to the first
+ character. The pattern is now applied starting at "x", and so the
+ (*COMMIT) causes the match to fail without trying any other starting
points.
(*PRUNE) or (*PRUNE:NAME)
- This verb causes the match to fail at the current starting position in
+ This verb causes the match to fail at the current starting position in
the subject if there is a later matching failure that causes backtrack-
- ing to reach it. If the pattern is unanchored, the normal "bumpalong"
- advance to the next starting character then happens. Backtracking can
- occur as usual to the left of (*PRUNE), before it is reached, or when
- matching to the right of (*PRUNE), but if there is no match to the
- right, backtracking cannot cross (*PRUNE). In simple cases, the use of
- (*PRUNE) is just an alternative to an atomic group or possessive quan-
+ ing to reach it. If the pattern is unanchored, the normal "bumpalong"
+ advance to the next starting character then happens. Backtracking can
+ occur as usual to the left of (*PRUNE), before it is reached, or when
+ matching to the right of (*PRUNE), but if there is no match to the
+ right, backtracking cannot cross (*PRUNE). In simple cases, the use of
+ (*PRUNE) is just an alternative to an atomic group or possessive quan-
tifier, but there are some uses of (*PRUNE) that cannot be expressed in
- any other way. In an anchored pattern (*PRUNE) has the same effect as
+ any other way. In an anchored pattern (*PRUNE) has the same effect as
(*COMMIT).
The behaviour of (*PRUNE:NAME) is not the same as (*MARK:NAME)(*PRUNE).
It is like (*MARK:NAME) in that the name is remembered for passing back
- to the caller. However, (*SKIP:NAME) searches only for names set with
+ to the caller. However, (*SKIP:NAME) searches only for names set with
(*MARK), ignoring those set by (*COMMIT), (*PRUNE) or (*THEN).
(*SKIP)
- This verb, when given without a name, is like (*PRUNE), except that if
- the pattern is unanchored, the "bumpalong" advance is not to the next
+ This verb, when given without a name, is like (*PRUNE), except that if
+ the pattern is unanchored, the "bumpalong" advance is not to the next
character, but to the position in the subject where (*SKIP) was encoun-
- tered. (*SKIP) signifies that whatever text was matched leading up to
- it cannot be part of a successful match if there is a later mismatch.
+ tered. (*SKIP) signifies that whatever text was matched leading up to
+ it cannot be part of a successful match if there is a later mismatch.
Consider:
a+(*SKIP)b
- If the subject is "aaaac...", after the first match attempt fails
- (starting at the first character in the string), the starting point
+ If the subject is "aaaac...", after the first match attempt fails
+ (starting at the first character in the string), the starting point
skips on to start the next attempt at "c". Note that a possessive quan-
- tifer does not have the same effect as this example; although it would
- suppress backtracking during the first match attempt, the second
- attempt would start at the second character instead of skipping on to
+ tifer does not have the same effect as this example; although it would
+ suppress backtracking during the first match attempt, the second
+ attempt would start at the second character instead of skipping on to
"c".
(*SKIP:NAME)
- When (*SKIP) has an associated name, its behaviour is modified. When
- such a (*SKIP) is triggered, the previous path through the pattern is
- searched for the most recent (*MARK) that has the same name. If one is
- found, the "bumpalong" advance is to the subject position that corre-
- sponds to that (*MARK) instead of to where (*SKIP) was encountered. If
+ When (*SKIP) has an associated name, its behaviour is modified. When
+ such a (*SKIP) is triggered, the previous path through the pattern is
+ searched for the most recent (*MARK) that has the same name. If one is
+ found, the "bumpalong" advance is to the subject position that corre-
+ sponds to that (*MARK) instead of to where (*SKIP) was encountered. If
no (*MARK) with a matching name is found, the (*SKIP) is ignored.
- The search for a (*MARK) name uses the normal backtracking mechanism,
- which means that it does not see (*MARK) settings that are inside
+ The search for a (*MARK) name uses the normal backtracking mechanism,
+ which means that it does not see (*MARK) settings that are inside
atomic groups or assertions, because they are never re-entered by back-
tracking. Compare the following pcre2test examples:
@@ -8977,106 +8991,106 @@
0: b
1: b
- In the first example, the (*MARK) setting is in an atomic group, so it
+ In the first example, the (*MARK) setting is in an atomic group, so it
is not seen when (*SKIP:X) triggers, causing the (*SKIP) to be ignored.
- This allows the second branch of the pattern to be tried at the first
- character position. In the second example, the (*MARK) setting is not
- in an atomic group. This allows (*SKIP:X) to find the (*MARK) when it
+ This allows the second branch of the pattern to be tried at the first
+ character position. In the second example, the (*MARK) setting is not
+ in an atomic group. This allows (*SKIP:X) to find the (*MARK) when it
backtracks, and this causes a new matching attempt to start at the sec-
- ond character. This time, the (*MARK) is never seen because "a" does
+ ond character. This time, the (*MARK) is never seen because "a" does
not match "b", so the matcher immediately jumps to the second branch of
the pattern.
- Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It
- ignores names that are set by (*COMMIT:NAME), (*PRUNE:NAME) or
+ Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It
+ ignores names that are set by (*COMMIT:NAME), (*PRUNE:NAME) or
(*THEN:NAME).
(*THEN) or (*THEN:NAME)
- This verb causes a skip to the next innermost alternative when back-
- tracking reaches it. That is, it cancels any further backtracking
- within the current alternative. Its name comes from the observation
+ This verb causes a skip to the next innermost alternative when back-
+ tracking reaches it. That is, it cancels any further backtracking
+ within the current alternative. Its name comes from the observation
that it can be used for a pattern-based if-then-else block:
( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ...
- If the COND1 pattern matches, FOO is tried (and possibly further items
- after the end of the group if FOO succeeds); on failure, the matcher
- skips to the second alternative and tries COND2, without backtracking
- into COND1. If that succeeds and BAR fails, COND3 is tried. If subse-
- quently BAZ fails, there are no more alternatives, so there is a back-
- track to whatever came before the entire group. If (*THEN) is not
+ If the COND1 pattern matches, FOO is tried (and possibly further items
+ after the end of the group if FOO succeeds); on failure, the matcher
+ skips to the second alternative and tries COND2, without backtracking
+ into COND1. If that succeeds and BAR fails, COND3 is tried. If subse-
+ quently BAZ fails, there are no more alternatives, so there is a back-
+ track to whatever came before the entire group. If (*THEN) is not
inside an alternation, it acts like (*PRUNE).
- The behaviour of (*THEN:NAME) is not the same as (*MARK:NAME)(*THEN).
+ The behaviour of (*THEN:NAME) is not the same as (*MARK:NAME)(*THEN).
It is like (*MARK:NAME) in that the name is remembered for passing back
- to the caller. However, (*SKIP:NAME) searches only for names set with
+ to the caller. However, (*SKIP:NAME) searches only for names set with
(*MARK), ignoring those set by (*COMMIT), (*PRUNE) and (*THEN).
- A subpattern that does not contain a | character is just a part of the
- enclosing alternative; it is not a nested alternation with only one
- alternative. The effect of (*THEN) extends beyond such a subpattern to
- the enclosing alternative. Consider this pattern, where A, B, etc. are
- complex pattern fragments that do not contain any | characters at this
+ A subpattern that does not contain a | character is just a part of the
+ enclosing alternative; it is not a nested alternation with only one
+ alternative. The effect of (*THEN) extends beyond such a subpattern to
+ the enclosing alternative. Consider this pattern, where A, B, etc. are
+ complex pattern fragments that do not contain any | characters at this
level:
A (B(*THEN)C) | D
- If A and B are matched, but there is a failure in C, matching does not
+ If A and B are matched, but there is a failure in C, matching does not
backtrack into A; instead it moves to the next alternative, that is, D.
- However, if the subpattern containing (*THEN) is given an alternative,
+ However, if the subpattern containing (*THEN) is given an alternative,
it behaves differently:
A (B(*THEN)C | (*FAIL)) | D
- The effect of (*THEN) is now confined to the inner subpattern. After a
+ The effect of (*THEN) is now confined to the inner subpattern. After a
failure in C, matching moves to (*FAIL), which causes the whole subpat-
- tern to fail because there are no more alternatives to try. In this
+ tern to fail because there are no more alternatives to try. In this
case, matching does now backtrack into A.
- Note that a conditional subpattern is not considered as having two
- alternatives, because only one is ever used. In other words, the |
+ Note that a conditional subpattern is not considered as having two
+ alternatives, because only one is ever used. In other words, the |
character in a conditional subpattern has a different meaning. Ignoring
white space, consider:
^.*? (?(?=a) a | b(*THEN)c )
- If the subject is "ba", this pattern does not match. Because .*? is
- ungreedy, it initially matches zero characters. The condition (?=a)
- then fails, the character "b" is matched, but "c" is not. At this
- point, matching does not backtrack to .*? as might perhaps be expected
- from the presence of the | character. The conditional subpattern is
+ If the subject is "ba", this pattern does not match. Because .*? is
+ ungreedy, it initially matches zero characters. The condition (?=a)
+ then fails, the character "b" is matched, but "c" is not. At this
+ point, matching does not backtrack to .*? as might perhaps be expected
+ from the presence of the | character. The conditional subpattern is
part of the single alternative that comprises the whole pattern, and so
- the match fails. (If there was a backtrack into .*?, allowing it to
+ the match fails. (If there was a backtrack into .*?, allowing it to
match "b", the match would succeed.)
- The verbs just described provide four different "strengths" of control
+ The verbs just described provide four different "strengths" of control
when subsequent matching fails. (*THEN) is the weakest, carrying on the
- match at the next alternative. (*PRUNE) comes next, failing the match
- at the current starting position, but allowing an advance to the next
- character (for an unanchored pattern). (*SKIP) is similar, except that
+ match at the next alternative. (*PRUNE) comes next, failing the match
+ at the current starting position, but allowing an advance to the next
+ character (for an unanchored pattern). (*SKIP) is similar, except that
the advance may be more than one character. (*COMMIT) is the strongest,
causing the entire match to fail.
More than one backtracking verb
- If more than one backtracking verb is present in a pattern, the one
- that is backtracked onto first acts. For example, consider this pat-
+ If more than one backtracking verb is present in a pattern, the one
+ that is backtracked onto first acts. For example, consider this pat-
tern, where A, B, etc. are complex pattern fragments:
(A(*COMMIT)B(*THEN)C|ABD)
- If A matches but B fails, the backtrack to (*COMMIT) causes the entire
+ If A matches but B fails, the backtrack to (*COMMIT) causes the entire
match to fail. However, if A and B match, but C fails, the backtrack to
- (*THEN) causes the next alternative (ABD) to be tried. This behaviour
- is consistent, but is not always the same as Perl's. It means that if
- two or more backtracking verbs appear in succession, all the the last
+ (*THEN) causes the next alternative (ABD) to be tried. This behaviour
+ is consistent, but is not always the same as Perl's. It means that if
+ two or more backtracking verbs appear in succession, all the the last
of them has no effect. Consider this example:
...(*COMMIT)(*PRUNE)...
If there is a matching failure to the right, backtracking onto (*PRUNE)
- causes it to be triggered, and its action is taken. There can never be
+ causes it to be triggered, and its action is taken. There can never be
a backtrack onto (*COMMIT).
Backtracking verbs in repeated groups
@@ -9086,42 +9100,42 @@
/(a(*COMMIT)b)+ac/
- If the subject is "abac", Perl matches unless its optimizations are
- disabled, but PCRE2 always fails because the (*COMMIT) in the second
+ If the subject is "abac", Perl matches unless its optimizations are
+ disabled, but PCRE2 always fails because the (*COMMIT) in the second
repeat of the group acts.
Backtracking verbs in assertions
- (*FAIL) in any assertion has its normal effect: it forces an immediate
- backtrack. The behaviour of the other backtracking verbs depends on
- whether or not the assertion is standalone or acting as the condition
+ (*FAIL) in any assertion has its normal effect: it forces an immediate
+ backtrack. The behaviour of the other backtracking verbs depends on
+ whether or not the assertion is standalone or acting as the condition
in a conditional subpattern.
- (*ACCEPT) in a standalone positive assertion causes the assertion to
- succeed without any further processing; captured strings and a (*MARK)
- name (if set) are retained. In a standalone negative assertion,
- (*ACCEPT) causes the assertion to fail without any further processing;
+ (*ACCEPT) in a standalone positive assertion causes the assertion to
+ succeed without any further processing; captured strings and a (*MARK)
+ name (if set) are retained. In a standalone negative assertion,
+ (*ACCEPT) causes the assertion to fail without any further processing;
captured substrings and any (*MARK) name are discarded.
- If the assertion is a condition, (*ACCEPT) causes the condition to be
- true for a positive assertion and false for a negative one; captured
+ If the assertion is a condition, (*ACCEPT) causes the condition to be
+ true for a positive assertion and false for a negative one; captured
substrings are retained in both cases.
The remaining verbs act only when a later failure causes a backtrack to
- reach them. This means that their effect is confined to the assertion,
+ reach them. This means that their effect is confined to the assertion,
because lookaround assertions are atomic. A backtrack that occurs after
an assertion is complete does not jump back into the assertion. Note in
- particular that a (*MARK) name that is set in an assertion is not
+ particular that a (*MARK) name that is set in an assertion is not
"seen" by an instance of (*SKIP:NAME) latter in the pattern.
- The effect of (*THEN) is not allowed to escape beyond an assertion. If
- there are no more branches to try, (*THEN) causes a positive assertion
+ The effect of (*THEN) is not allowed to escape beyond an assertion. If
+ there are no more branches to try, (*THEN) causes a positive assertion
to be false, and a negative assertion to be true.
- The other backtracking verbs are not treated specially if they appear
- in a standalone positive assertion. In a conditional positive asser-
+ The other backtracking verbs are not treated specially if they appear
+ in a standalone positive assertion. In a conditional positive asser-
tion, backtracking (from within the assertion) into (*COMMIT), (*SKIP),
- or (*PRUNE) causes the condition to be false. However, for both stand-
+ or (*PRUNE) causes the condition to be false. However, for both stand-
alone and conditional negative assertions, backtracking into (*COMMIT),
(*SKIP), or (*PRUNE) causes the assertion to be true, without consider-
ing any further alternative branches.
@@ -9128,31 +9142,31 @@
Backtracking verbs in subroutines
- These behaviours occur whether or not the subpattern is called recur-
+ These behaviours occur whether or not the subpattern is called recur-
sively.
- (*ACCEPT) in a subpattern called as a subroutine causes the subroutine
- match to succeed without any further processing. Matching then contin-
- ues after the subroutine call. Perl documents this behaviour. Perl's
+ (*ACCEPT) in a subpattern called as a subroutine causes the subroutine
+ match to succeed without any further processing. Matching then contin-
+ ues after the subroutine call. Perl documents this behaviour. Perl's
treatment of the other verbs in subroutines is different in some cases.
- (*FAIL) in a subpattern called as a subroutine has its normal effect:
+ (*FAIL) in a subpattern called as a subroutine has its normal effect:
it forces an immediate backtrack.
- (*COMMIT), (*SKIP), and (*PRUNE) cause the subroutine match to fail
+ (*COMMIT), (*SKIP), and (*PRUNE) cause the subroutine match to fail
when triggered by being backtracked to in a subpattern called as a sub-
routine. There is then a backtrack at the outer level.
(*THEN), when triggered, skips to the next alternative in the innermost
enclosing group within the subpattern that has alternatives (its normal
- behaviour). However, if there is no such group within the subroutine
- subpattern, the subroutine match fails and there is a backtrack at the
+ behaviour). However, if there is no such group within the subroutine
+ subpattern, the subroutine match fails and there is a backtrack at the
outer level.
SEE ALSO
- pcre2api(3), pcre2callout(3), pcre2matching(3), pcre2syntax(3),
+ pcre2api(3), pcre2callout(3), pcre2matching(3), pcre2syntax(3),
pcre2(3).
@@ -9165,7 +9179,7 @@
REVISION
- Last updated: 04 September 2018
+ Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
------------------------------------------------------------------------------
Modified: code/trunk/doc/pcre2_set_compile_extra_options.3
===================================================================
--- code/trunk/doc/pcre2_set_compile_extra_options.3 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2_set_compile_extra_options.3 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1,4 +1,4 @@
-.TH PCRE2_SET_COMPILE_EXTRA_OPTIONS 3 "16 June 2017" "PCRE2 10.30"
+.TH PCRE2_SET_COMPILE_EXTRA_OPTIONS 3 "21 September 2018" "PCRE2 10.33"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.SH SYNOPSIS
@@ -24,6 +24,7 @@
.\" JOIN
PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL Treat all invalid escapes as
a literal following character
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF Interpret \er as \en
PCRE2_EXTRA_MATCH_LINE Pattern matches whole lines
PCRE2_EXTRA_MATCH_WORD Pattern matches "words"
.sp
Modified: code/trunk/doc/pcre2api.3
===================================================================
--- code/trunk/doc/pcre2api.3 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2api.3 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1,4 +1,4 @@
-.TH PCRE2API 3 "18 September 2018" "PCRE2 10.33"
+.TH PCRE2API 3 "21 September 2018" "PCRE2 10.33"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.sp
@@ -1825,6 +1825,14 @@
that typos in patterns may go undetected and have unexpected results. This is a
dangerous option. Use with care.
.sp
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF
+.sp
+There are some legacy applications where the escape sequence \er in a pattern
+is expected to match a newline. If this option is set, \er in a pattern is
+converted to \en so that it matches a LF (linefeed) instead of a CR (carriage
+return) character. The option does not affect a literal CR in the pattern, nor
+does it affect CR specified as an explicit code point such as \ex{0D}.
+.sp
PCRE2_EXTRA_MATCH_LINE
.sp
This option is provided for use by the \fB-x\fP option of \fBpcre2grep\fP. It
@@ -3729,6 +3737,6 @@
.rs
.sp
.nf
-Last updated: 18 September 2018
+Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
.fi
Modified: code/trunk/doc/pcre2pattern.3
===================================================================
--- code/trunk/doc/pcre2pattern.3 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2pattern.3 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1,4 +1,4 @@
-.TH PCRE2PATTERN 3 "04 September 2018" "PCRE2 10.32"
+.TH PCRE2PATTERN 3 "21 September 2018" "PCRE2 10.33"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.SH "PCRE2 REGULAR EXPRESSION DETAILS"
@@ -370,7 +370,7 @@
\ee escape (hex 1B)
\ef form feed (hex 0C)
\en linefeed (hex 0A)
- \er carriage return (hex 0D)
+ \er carriage return (hex 0D) (but see below)
\et tab (hex 09)
\e0dd character with octal code 0dd
\eddd character with octal code ddd, or backreference
@@ -380,6 +380,11 @@
\eN{U+hhh..} character with Unicode hex code point hhh..
\euhhhh character with hex code hhhh (when PCRE2_ALT_BSUX is set)
.sp
+There are some legacy applications where the escape sequence \er is expected to
+match a newline. If the PCRE2_EXTRA_ESCAPED_CR_IS_LF option is set, \er in a
+pattern is converted to \en so that it matches a LF (linefeed) instead of a CR
+(carriage return) character.
+.P
The \eN{U+hhh..} escape sequence is recognized only when the PCRE2_UTF option
is set, that is, when PCRE2 is operating in a Unicode mode. Perl also uses
\eN{name} to specify characters by Unicode name; PCRE2 does not support this.
@@ -3655,6 +3660,6 @@
.rs
.sp
.nf
-Last updated: 04 September 2018
+Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
.fi
Modified: code/trunk/doc/pcre2test.1
===================================================================
--- code/trunk/doc/pcre2test.1 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2test.1 2018-09-21 16:59:48 UTC (rev 1017)
@@ -1,4 +1,4 @@
-.TH PCRE2TEST 1 "17 September 2018" "PCRE 10.33"
+.TH PCRE2TEST 1 "21 September 2018" "PCRE 10.33"
.SH NAME
pcre2test - a program for testing Perl-compatible regular expressions.
.SH SYNOPSIS
@@ -565,6 +565,7 @@
/s dotall set PCRE2_DOTALL
dupnames set PCRE2_DUPNAMES
endanchored set PCRE2_ENDANCHORED
+ escaped_cr_is_lf set PCRE2_EXTRA_ESCAPED_CR_IS_LF
/x extended set PCRE2_EXTENDED
/xx extended_more set PCRE2_EXTENDED_MORE
firstline set PCRE2_FIRSTLINE
@@ -2021,6 +2022,6 @@
.rs
.sp
.nf
-Last updated: 17 September 2018
+Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
.fi
Modified: code/trunk/doc/pcre2test.txt
===================================================================
--- code/trunk/doc/pcre2test.txt 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/doc/pcre2test.txt 2018-09-21 16:59:48 UTC (rev 1017)
@@ -544,6 +544,7 @@
/s dotall set PCRE2_DOTALL
dupnames set PCRE2_DUPNAMES
endanchored set PCRE2_ENDANCHORED
+ escaped_cr_is_lf set PCRE2_EXTRA_ESCAPED_CR_IS_LF
/x extended set PCRE2_EXTENDED
/xx extended_more set PCRE2_EXTENDED_MORE
firstline set PCRE2_FIRSTLINE
@@ -1852,5 +1853,5 @@
REVISION
- Last updated: 17 September 2018
+ Last updated: 21 September 2018
Copyright (c) 1997-2018 University of Cambridge.
Modified: code/trunk/src/pcre2.h.in
===================================================================
--- code/trunk/src/pcre2.h.in 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/src/pcre2.h.in 2018-09-21 16:59:48 UTC (rev 1017)
@@ -158,6 +158,7 @@
#define PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL 0x00000002u /* C */
#define PCRE2_EXTRA_MATCH_WORD 0x00000004u /* C */
#define PCRE2_EXTRA_MATCH_LINE 0x00000008u /* C */
+#define PCRE2_EXTRA_ESCAPED_CR_IS_LF 0x00000010u /* C */
/* These are for pcre2_jit_compile(). */
Modified: code/trunk/src/pcre2_compile.c
===================================================================
--- code/trunk/src/pcre2_compile.c 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/src/pcre2_compile.c 2018-09-21 16:59:48 UTC (rev 1017)
@@ -714,7 +714,8 @@
#define PUBLIC_COMPILE_EXTRA_OPTIONS \
(PUBLIC_LITERAL_COMPILE_EXTRA_OPTIONS| \
- PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES|PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL)
+ PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES|PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL| \
+ PCRE2_EXTRA_ESCAPED_CR_IS_LF)
/* Compile time error code numbers. They are given names so that they can more
easily be tracked. When a new number is added, the tables called eint1 and
@@ -1398,7 +1399,7 @@
errorcodeptr points to the errorcode variable (containing zero)
options the current options bits
isclass TRUE if inside a character class
- cb compile data block
+ cb compile data block or NULL when called from pcre2_substitute()
Returns: zero => a data character
positive => a special escape sequence
@@ -1429,15 +1430,27 @@
/* Non-alphanumerics are literals, so we just leave the value in c. An initial
value test saves a memory lookup for code points outside the alphanumeric
-range. Otherwise, do a table lookup. A non-zero result is something that can be
-returned immediately. Otherwise further processing is required. */
+range. */
if (c < ESCAPES_FIRST || c > ESCAPES_LAST) {} /* Definitely literal */
+/* Otherwise, do a table lookup. Non-zero values need little processing here. A
+positive value is a literal value for something like \n. A negative value is
+the negation of one of the ESC_ macros that is passed back for handling by the
+calling function. Some extra checking is needed for \N because only \N{U+dddd}
+is supported. If the value is zero, further processing is handled below. */
+
else if ((i = escapes[c - ESCAPES_FIRST]) != 0)
{
- if (i > 0) c = (uint32_t)i; else /* Positive is a data character */
+ if (i > 0)
{
+ c = (uint32_t)i;
+ if (cb != NULL && c == CHAR_CR &&
+ (cb->cx->extra_options & PCRE2_EXTRA_ESCAPED_CR_IS_LF) != 0)
+ c = CHAR_LF;
+ }
+ else /* Negative table entry */
+ {
escape = -i; /* Else return a special escape */
if (cb != NULL && (escape == ESC_P || escape == ESC_p || escape == ESC_X))
cb->external_flags |= PCRE2_HASBKPORX; /* Note \P, \p, or \X */
@@ -1486,9 +1499,9 @@
}
}
-/* Escapes that need further processing, including those that are unknown.
-When called from pcre2_substitute(), only \c, \o, and \x are recognized (and \u
-when BSUX is set). */
+/* Escapes that need further processing, including those that are unknown, have
+a zero entry in the lookup table. When called from pcre2_substitute(), only \c,
+\o, and \x are recognized (and \u when BSUX is set). */
else
{
Modified: code/trunk/src/pcre2test.c
===================================================================
--- code/trunk/src/pcre2test.c 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/src/pcre2test.c 2018-09-21 16:59:48 UTC (rev 1017)
@@ -629,6 +629,7 @@
{ "dotall", MOD_PATP, MOD_OPT, PCRE2_DOTALL, PO(options) },
{ "dupnames", MOD_PATP, MOD_OPT, PCRE2_DUPNAMES, PO(options) },
{ "endanchored", MOD_PD, MOD_OPT, PCRE2_ENDANCHORED, PD(options) },
+ { "escaped_cr_is_lf", MOD_CTC, MOD_OPT, PCRE2_EXTRA_ESCAPED_CR_IS_LF, CO(extra_options) },
{ "expand", MOD_PAT, MOD_CTL, CTL_EXPAND, PO(control) },
{ "extended", MOD_PATP, MOD_OPT, PCRE2_EXTENDED, PO(options) },
{ "extended_more", MOD_PATP, MOD_OPT, PCRE2_EXTENDED_MORE, PO(options) },
@@ -4173,12 +4174,13 @@
const char *after)
{
if (options == 0) fprintf(outfile, "%s <none>%s", before, after);
-else fprintf(outfile, "%s%s%s%s%s%s",
+else fprintf(outfile, "%s%s%s%s%s%s%s",
before,
((options & PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES) != 0)? " allow_surrogate_escapes" : "",
((options & PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL) != 0)? " bad_escape_is_literal" : "",
((options & PCRE2_EXTRA_MATCH_WORD) != 0)? " match_word" : "",
((options & PCRE2_EXTRA_MATCH_LINE) != 0)? " match_line" : "",
+ ((options & PCRE2_EXTRA_ESCAPED_CR_IS_LF) != 0)? " escaped_cr_is_lf" : "",
after);
}
Modified: code/trunk/testdata/testinput2
===================================================================
--- code/trunk/testdata/testinput2 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/testdata/testinput2 2018-09-21 16:59:48 UTC (rev 1017)
@@ -5517,4 +5517,12 @@
/a(b)c|xyz/g,replace=<$0>,substitute_callout
abcdefabcpqr
+/abc\rdef/
+ abc\ndef
+
+/abc\rdef\x{0d}xyz/escaped_cr_is_lf
+ abc\ndef\rxyz
+\= Expect no match
+ abc\ndef\nxyz
+
# End of testinput2
Modified: code/trunk/testdata/testoutput2
===================================================================
--- code/trunk/testdata/testoutput2 2018-09-21 07:24:34 UTC (rev 1016)
+++ code/trunk/testdata/testoutput2 2018-09-21 16:59:48 UTC (rev 1017)
@@ -16801,6 +16801,17 @@
Old 6 9 New 8 13
2: <abc>def<abc>pqr
+/abc\rdef/
+ abc\ndef
+No match
+
+/abc\rdef\x{0d}xyz/escaped_cr_is_lf
+ abc\ndef\rxyz
+ 0: abc\x0adef\x0dxyz
+\= Expect no match
+ abc\ndef\nxyz
+No match
+
# End of testinput2
Error -70: PCRE2_ERROR_BADDATA (unknown error number)
Error -62: bad serialized data
