Revision: 180
http://www.exim.org/viewvc/pcre2?view=rev&revision=180
Author: ph10
Date: 2015-01-03 17:40:06 +0000 (Sat, 03 Jan 2015)
Log Message:
-----------
Update pcre2grep documentation to give more details of -M matching.
Modified Paths:
--------------
code/trunk/doc/html/pcre2grep.html
code/trunk/doc/pcre2grep.1
code/trunk/doc/pcre2grep.txt
Modified: code/trunk/doc/html/pcre2grep.html
===================================================================
--- code/trunk/doc/html/pcre2grep.html 2015-01-02 17:09:16 UTC (rev 179)
+++ code/trunk/doc/html/pcre2grep.html 2015-01-03 17:40:06 UTC (rev 180)
@@ -67,22 +67,23 @@
standard input can also be referenced by a name consisting of a single hyphen.
For example:
<pre>
- pcre2grep some-pattern /file1 - /file3
+ pcre2grep some-pattern file1 - file3
</pre>
-By default, each line that matches a pattern is copied to the standard
-output, and if there is more than one file, the file name is output at the
-start of each line, followed by a colon. However, there are options that can
-change how <b>pcre2grep</b> behaves. In particular, the <b>-M</b> option makes it
-possible to search for patterns that span line boundaries. What defines a line
-boundary is controlled by the <b>-N</b> (<b>--newline</b>) option.
+Input files are searched line by line. By default, each line that matches a
+pattern is copied to the standard output, and if there is more than one file,
+the file name is output at the start of each line, followed by a colon.
+However, there are options that can change how <b>pcre2grep</b> behaves. In
+particular, the <b>-M</b> option makes it possible to search for strings that
+span line boundaries. What defines a line boundary is controlled by the
+<b>-N</b> (<b>--newline</b>) option.
</P>
<P>
The amount of memory used for buffering files that are being scanned is
controlled by a parameter that can be set by the <b>--buffer-size</b> option.
-The default value for this parameter is specified when <b>pcre2grep</b> is built,
-with the default default being 20K. A block of memory three times this size is
-used (to allow for buffering "before" and "after" lines). An error occurs if a
-line overflows the buffer.
+The default value for this parameter is specified when <b>pcre2grep</b> is
+built, with the default default being 20K. A block of memory three times this
+size is used (to allow for buffering "before" and "after" lines). An error
+occurs if a line overflows the buffer.
</P>
<P>
Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the greater.
@@ -149,11 +150,11 @@
<b>--</b>
This terminates the list of options. It is useful if the next item on the
command line starts with a hyphen but is not an option. This allows for the
-processing of patterns and filenames that start with hyphens.
+processing of patterns and file names that start with hyphens.
</P>
<P>
<b>-A</b> <i>number</i>, <b>--after-context=</b><i>number</i>
-Output <i>number</i> lines of context after each matching line. If filenames
+Output <i>number</i> lines of context after each matching line. If file names
and/or line numbers are being output, a hyphen separator is used instead of a
colon for the context lines. A line containing "--" is output between each
group of lines, unless they are in fact contiguous in the input file. The value
@@ -167,7 +168,7 @@
</P>
<P>
<b>-B</b> <i>number</i>, <b>--before-context=</b><i>number</i>
-Output <i>number</i> lines of context before each matching line. If filenames
+Output <i>number</i> lines of context before each matching line. If file names
and/or line numbers are being output, a hyphen separator is used instead of a
colon for the context lines. A line containing "--" is output between each
group of lines, unless they are in fact contiguous in the input file. The value
@@ -184,7 +185,8 @@
succeeds, the output may be binary garbage, which can have nasty effects if
sent to a terminal. If the word is "without-match", which is equivalent to the
<b>-I</b> option, binary files are not processed at all; they are assumed not to
-be of interest.
+be of interest and are skipped without causing any output or affecting the
+return code.
</P>
<P>
<b>--buffer-size=</b><i>number</i>
@@ -198,10 +200,15 @@
</P>
<P>
<b>-c</b>, <b>--count</b>
-Do not output individual lines from the files that are being scanned; instead
-output the number of lines that would otherwise have been shown. If no lines
-are selected, the number zero is output. If several files are are being
-scanned, a count is output for each of them. However, if the
+Do not output lines from the files that are being scanned; instead output the
+number of matches (or non-matches if <b>-v</b> is used) that would otherwise
+have caused lines to be shown. By default, this count is the same as the number
+of suppressed lines, but if the <b>-M</b> (multiline) option is used (without
+<b>-v</b>), there may be more suppressed lines than the number of matches.
+<br>
+<br>
+If no lines are selected, the number zero is output. If several files are are
+being scanned, a count is output for each of them. However, if the
<b>--files-with-matches</b> option is also used, only those files whose counts
are greater than zero are listed. When <b>-c</b> is used, the <b>-A</b>,
<b>-B</b>, and <b>-C</b> options are ignored.
@@ -271,10 +278,10 @@
Files (but not directories) whose names match the pattern are skipped without
being processed. This applies to all files, whether listed on the command line,
obtained from <b>--file-list</b>, or by scanning a directory. The pattern is a
-PCRE2 regular expression, and is matched against the final component of the file
-name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not
-apply to this pattern. The option may be given any number of times in order to
-specify multiple patterns. If a file name matches both an <b>--include</b>
+PCRE2 regular expression, and is matched against the final component of the
+file name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do
+not apply to this pattern. The option may be given any number of times in order
+to specify multiple patterns. If a file name matches both an <b>--include</b>
and an <b>--exclude</b> pattern, it is excluded. There is no short form for this
option.
</P>
@@ -323,7 +330,7 @@
<br>
<br>
If this option is given more than once, all the specified files are
-read. A data line is output if any of the patterns match it. A filename can
+read. A data line is output if any of the patterns match it. A file name can
be given as "-" to refer to the standard input. When <b>-f</b> is used, patterns
specified on the command line using <b>-e</b> may also be present; they are
tested before the file's patterns. However, no other pattern is taken from the
@@ -334,7 +341,7 @@
Read a list of files and/or directories that are to be scanned from the given
file, one per line. Trailing white space is removed from each line, and blank
lines are ignored. These paths are processed before any that are listed on the
-command line. The filename can be given as "-" to refer to the standard input.
+command line. The file name can be given as "-" to refer to the standard input.
If <b>--file</b> and <b>--file-list</b> are both specified as "-", patterns are
read first. This is useful only when the standard input is a terminal, from
which further lines (the list of files) can be read after an end-of-file
@@ -352,17 +359,18 @@
</P>
<P>
<b>-H</b>, <b>--with-filename</b>
-Force the inclusion of the filename at the start of output lines when searching
-a single file. By default, the filename is not shown in this case. For matching
-lines, the filename is followed by a colon; for context lines, a hyphen
-separator is used. If a line number is also being output, it follows the file
-name.
+Force the inclusion of the file name at the start of output lines when
+searching a single file. By default, the file name is not shown in this case.
+For matching lines, the file name is followed by a colon; for context lines, a
+hyphen separator is used. If a line number is also being output, it follows the
+file name. When the <b>-M</b> option causes a pattern to match more than one
+line, only the first is preceded by the file name.
</P>
<P>
<b>-h</b>, <b>--no-filename</b>
-Suppress the output filenames when searching multiple files. By default,
-filenames are shown when multiple files are searched. For matching lines, the
-filename is followed by a colon; for context lines, a hyphen separator is used.
+Suppress the output file names when searching multiple files. By default,
+file names are shown when multiple files are searched. For matching lines, the
+file name is followed by a colon; for context lines, a hyphen separator is used.
If a line number is also being output, it follows the file name.
</P>
<P>
@@ -373,7 +381,7 @@
</P>
<P>
<b>-I</b>
-Treat binary files as never matching. This is equivalent to
+Ignore binary files. This is equivalent to
<b>--binary-files</b>=<i>without-match</i>.
</P>
<P>
@@ -406,8 +414,8 @@
are processed are those that match one of the patterns (and do not match an
<b>--exclude-dir</b> pattern). This applies to all directories, whether listed
on the command line, obtained from <b>--file-list</b>, or by scanning a parent
-directory. The pattern is a PCRE2 regular expression, and is matched against the
-final component of the directory name, not the entire path. The <b>-F</b>,
+directory. The pattern is a PCRE2 regular expression, and is matched against
+the final component of the directory name, not the entire path. The <b>-F</b>,
<b>-w</b>, and <b>-x</b> options do not apply to this pattern. The option may be
given any number of times. If a directory matches both <b>--include-dir</b> and
<b>--exclude-dir</b>, it is excluded. There is no short form for this option.
@@ -442,8 +450,8 @@
is currently possible only in Unix-like environments). Output to terminal is
normally automatically flushed by the operating system. This option can be
useful when the input or output is attached to a pipe and you do not want
-<b>pcre2grep</b> to buffer up large amounts of data. However, its use will affect
-performance, and the <b>-M</b> (multiline) option ceases to work.
+<b>pcre2grep</b> to buffer up large amounts of data. However, its use will
+affect performance, and the <b>-M</b> (multiline) option ceases to work.
</P>
<P>
<b>--line-offsets</b>
@@ -497,18 +505,33 @@
Allow patterns to match more than one line. When this option is given, patterns
may usefully contain literal newline characters and internal occurrences of ^
and $ characters. The output for a successful match may consist of more than
-one line, the last of which is the one in which the match ended. If the matched
-string ends with a newline sequence the output ends at the end of that line.
+one line. The first is the line in which the match started, and the last is the
+line in which the match ended. If the matched string ends with a newline
+sequence the output ends at the end of that line.
<br>
<br>
When this option is set, the PCRE2 library is called in "multiline" mode.
+However, <b>pcre2grep</b> still processes the input line by line. The difference
+is that a matched string may extend past the end of a line and continue on
+one or more subsequent lines. The newline sequence must be matched as part of
+the pattern. For example, to find the phrase "regular expression" in a file
+where "regular" might be at the end of a line and "expression" at the start of
+the next line, you could use this command:
+<pre>
+ pcre2grep -M 'regular\s+expression' <file>
+</pre>
+The \s escape sequence matches any white space character, including newlines,
+and is followed by + so as to match trailing white space on the first line as
+well as possibly handling a two-character newline sequence.
+<br>
+<br>
There is a limit to the number of lines that can be matched, imposed by the way
that <b>pcre2grep</b> buffers the input file as it scans it. However,
-<b>pcre2grep</b> ensures that at least 8K characters or the rest of the document
+<b>pcre2grep</b> ensures that at least 8K characters or the rest of the file
(whichever is the shorter) are available for forward matching, and similarly
the previous 8K characters (or all the previous characters, if fewer than 8K)
-are guaranteed to be available for lookbehind assertions. This option does not
-work when input is read line by line (see \fP--line-buffered\fP.)
+are guaranteed to be available for lookbehind assertions. The <b>-M</b> option
+does not work when input is read line by line (see \fP--line-buffered\fP.)
</P>
<P>
<b>-N</b> <i>newline-type</i>, <b>--newline</b>=<i>newline-type</i>
@@ -526,9 +549,9 @@
This is normally the standard sequence for the operating system. Unless
otherwise specified by this option, <b>pcre2grep</b> uses the library's default.
The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This
-makes it possible to use <b>pcre2grep</b> to scan files that have come from other
-environments without having to modify their line endings. If the data that is
-being scanned does not agree with the convention set by this option,
+makes it possible to use <b>pcre2grep</b> to scan files that have come from
+other environments without having to modify their line endings. If the data
+that is being scanned does not agree with the convention set by this option,
<b>pcre2grep</b> may behave in strange ways. Note that this option does not
apply to files specified by the <b>-f</b>, <b>--exclude-from</b>, or
<b>--include-from</b> options, which are expected to use the operating system's
@@ -537,9 +560,10 @@
<P>
<b>-n</b>, <b>--line-number</b>
Precede each output line by its line number in the file, followed by a colon
-for matching lines or a hyphen for context lines. If the filename is also being
-output, it precedes the line number. This option is forced if
-<b>--line-offsets</b> is used.
+for matching lines or a hyphen for context lines. If the file name is also
+being output, it precedes the line number. When the <b>-M</b> option causes a
+pattern to match more than one line, only the first is preceded by its line
+number. This option is forced if <b>--line-offsets</b> is used.
</P>
<P>
<b>--no-jit</b>
@@ -570,7 +594,7 @@
the same shell item, for example, -o3 or --only-matching=2. The comments given
for the non-argument case above also apply to this case. If the specified
capturing parentheses do not exist in the pattern, or were not set in the
-match, nothing is output unless the file name or line number are being printed.
+match, nothing is output unless the file name or line number are being output.
<br>
<br>
If this option is given multiple times, multiple substrings are output, in the
@@ -635,10 +659,10 @@
<b>-x</b>, <b>--line-regex</b>, <b>--line-regexp</b>
Force the patterns to be anchored (each must start matching at the beginning of
a line) and in addition, require them to match entire lines. This is equivalent
-to having ^ and $ characters at the start and end of each alternative branch in
-every pattern. This option applies only to the patterns that are matched
-against the contents of files; it does not apply to patterns specified by any
-of the <b>--include</b> or <b>--exclude</b> options.
+to having ^ and $ characters at the start and end of each alternative top-level
+branch in every pattern. This option applies only to the patterns that are
+matched against the contents of files; it does not apply to patterns specified
+by any of the <b>--include</b> or <b>--exclude</b> options.
</P>
<br><a name="SEC6" href="#TOC1">ENVIRONMENT VARIABLES</a><br>
<P>
@@ -677,7 +701,7 @@
<b>pcre2grep</b>. For example, the <b>--include</b> option's argument is a glob
for GNU <b>grep</b>, but a regular expression for <b>pcre2grep</b>. If both the
<b>-c</b> and <b>-l</b> options are given, GNU grep lists only file names,
-without counts, but <b>pcre2grep</b> gives the counts.
+without counts, but <b>pcre2grep</b> gives the counts as well.
</P>
<br><a name="SEC9" href="#TOC1">OPTIONS WITH DATA</a><br>
<P>
@@ -722,9 +746,9 @@
there are more than 20 such errors, <b>pcre2grep</b> gives up.
</P>
<P>
-The <b>--match-limit</b> option of <b>pcre2grep</b> can be used to set the overall
-resource limit; there is a second option called <b>--recursion-limit</b> that
-sets a limit on the amount of memory (usually stack) that is used (see the
+The <b>--match-limit</b> option of <b>pcre2grep</b> can be used to set the
+overall resource limit; there is a second option called <b>--recursion-limit</b>
+that sets a limit on the amount of memory (usually stack) that is used (see the
discussion of these options above).
</P>
<br><a name="SEC11" href="#TOC1">DIAGNOSTICS</a><br>
@@ -737,7 +761,7 @@
</P>
<br><a name="SEC12" href="#TOC1">SEE ALSO</a><br>
<P>
-<b>pcre2pattern</b>(3), <b>pcre2syntax</b>(3), <b>pcre2test</b>(1).
+<b>pcre2pattern</b>(3), <b>pcre2syntax</b>(3).
</P>
<br><a name="SEC13" href="#TOC1">AUTHOR</a><br>
<P>
@@ -750,9 +774,9 @@
</P>
<br><a name="SEC14" href="#TOC1">REVISION</a><br>
<P>
-Last updated: 23 November 2014
+Last updated: 03 January 2015
<br>
-Copyright © 1997-2014 University of Cambridge.
+Copyright © 1997-2015 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE2 index page</a>.
Modified: code/trunk/doc/pcre2grep.1
===================================================================
--- code/trunk/doc/pcre2grep.1 2015-01-02 17:09:16 UTC (rev 179)
+++ code/trunk/doc/pcre2grep.1 2015-01-03 17:40:06 UTC (rev 180)
@@ -1,4 +1,4 @@
-.TH PCRE2GREP 1 "23 November 2014" "PCRE2 10.00"
+.TH PCRE2GREP 1 "03 January 2015" "PCRE2 10.00"
.SH NAME
pcre2grep - a grep with Perl-compatible regular expressions.
.SH SYNOPSIS
@@ -41,21 +41,22 @@
standard input can also be referenced by a name consisting of a single hyphen.
For example:
.sp
- pcre2grep some-pattern /file1 - /file3
+ pcre2grep some-pattern file1 - file3
.sp
-By default, each line that matches a pattern is copied to the standard
-output, and if there is more than one file, the file name is output at the
-start of each line, followed by a colon. However, there are options that can
-change how \fBpcre2grep\fP behaves. In particular, the \fB-M\fP option makes it
-possible to search for patterns that span line boundaries. What defines a line
-boundary is controlled by the \fB-N\fP (\fB--newline\fP) option.
+Input files are searched line by line. By default, each line that matches a
+pattern is copied to the standard output, and if there is more than one file,
+the file name is output at the start of each line, followed by a colon.
+However, there are options that can change how \fBpcre2grep\fP behaves. In
+particular, the \fB-M\fP option makes it possible to search for strings that
+span line boundaries. What defines a line boundary is controlled by the
+\fB-N\fP (\fB--newline\fP) option.
.P
The amount of memory used for buffering files that are being scanned is
controlled by a parameter that can be set by the \fB--buffer-size\fP option.
-The default value for this parameter is specified when \fBpcre2grep\fP is built,
-with the default default being 20K. A block of memory three times this size is
-used (to allow for buffering "before" and "after" lines). An error occurs if a
-line overflows the buffer.
+The default value for this parameter is specified when \fBpcre2grep\fP is
+built, with the default default being 20K. A block of memory three times this
+size is used (to allow for buffering "before" and "after" lines). An error
+occurs if a line overflows the buffer.
.P
Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the greater.
BUFSIZ is defined in \fB<stdio.h>\fP. When there is more than one pattern
@@ -122,10 +123,10 @@
\fB--\fP
This terminates the list of options. It is useful if the next item on the
command line starts with a hyphen but is not an option. This allows for the
-processing of patterns and filenames that start with hyphens.
+processing of patterns and file names that start with hyphens.
.TP
\fB-A\fP \fInumber\fP, \fB--after-context=\fP\fInumber\fP
-Output \fInumber\fP lines of context after each matching line. If filenames
+Output \fInumber\fP lines of context after each matching line. If file names
and/or line numbers are being output, a hyphen separator is used instead of a
colon for the context lines. A line containing "--" is output between each
group of lines, unless they are in fact contiguous in the input file. The value
@@ -137,7 +138,7 @@
\fB--binary-files\fP=\fItext\fP.
.TP
\fB-B\fP \fInumber\fP, \fB--before-context=\fP\fInumber\fP
-Output \fInumber\fP lines of context before each matching line. If filenames
+Output \fInumber\fP lines of context before each matching line. If file names
and/or line numbers are being output, a hyphen separator is used instead of a
colon for the context lines. A line containing "--" is output between each
group of lines, unless they are in fact contiguous in the input file. The value
@@ -153,7 +154,8 @@
succeeds, the output may be binary garbage, which can have nasty effects if
sent to a terminal. If the word is "without-match", which is equivalent to the
\fB-I\fP option, binary files are not processed at all; they are assumed not to
-be of interest.
+be of interest and are skipped without causing any output or affecting the
+return code.
.TP
\fB--buffer-size=\fP\fInumber\fP
Set the parameter that controls how much memory is used for buffering files
@@ -164,10 +166,14 @@
This is equivalent to setting both \fB-A\fP and \fB-B\fP to the same value.
.TP
\fB-c\fP, \fB--count\fP
-Do not output individual lines from the files that are being scanned; instead
-output the number of lines that would otherwise have been shown. If no lines
-are selected, the number zero is output. If several files are are being
-scanned, a count is output for each of them. However, if the
+Do not output lines from the files that are being scanned; instead output the
+number of matches (or non-matches if \fB-v\fP is used) that would otherwise
+have caused lines to be shown. By default, this count is the same as the number
+of suppressed lines, but if the \fB-M\fP (multiline) option is used (without
+\fB-v\fP), there may be more suppressed lines than the number of matches.
+.sp
+If no lines are selected, the number zero is output. If several files are are
+being scanned, a count is output for each of them. However, if the
\fB--files-with-matches\fP option is also used, only those files whose counts
are greater than zero are listed. When \fB-c\fP is used, the \fB-A\fP,
\fB-B\fP, and \fB-C\fP options are ignored.
@@ -229,10 +235,10 @@
Files (but not directories) whose names match the pattern are skipped without
being processed. This applies to all files, whether listed on the command line,
obtained from \fB--file-list\fP, or by scanning a directory. The pattern is a
-PCRE2 regular expression, and is matched against the final component of the file
-name, not the entire path. The \fB-F\fP, \fB-w\fP, and \fB-x\fP options do not
-apply to this pattern. The option may be given any number of times in order to
-specify multiple patterns. If a file name matches both an \fB--include\fP
+PCRE2 regular expression, and is matched against the final component of the
+file name, not the entire path. The \fB-F\fP, \fB-w\fP, and \fB-x\fP options do
+not apply to this pattern. The option may be given any number of times in order
+to specify multiple patterns. If a file name matches both an \fB--include\fP
and an \fB--exclude\fP pattern, it is excluded. There is no short form for this
option.
.TP
@@ -276,7 +282,7 @@
alternatives in the description of \fB-e\fP above.
.sp
If this option is given more than once, all the specified files are
-read. A data line is output if any of the patterns match it. A filename can
+read. A data line is output if any of the patterns match it. A file name can
be given as "-" to refer to the standard input. When \fB-f\fP is used, patterns
specified on the command line using \fB-e\fP may also be present; they are
tested before the file's patterns. However, no other pattern is taken from the
@@ -286,7 +292,7 @@
Read a list of files and/or directories that are to be scanned from the given
file, one per line. Trailing white space is removed from each line, and blank
lines are ignored. These paths are processed before any that are listed on the
-command line. The filename can be given as "-" to refer to the standard input.
+command line. The file name can be given as "-" to refer to the standard input.
If \fB--file\fP and \fB--file-list\fP are both specified as "-", patterns are
read first. This is useful only when the standard input is a terminal, from
which further lines (the list of files) can be read after an end-of-file
@@ -302,16 +308,17 @@
and \fB--only-matching\fP.
.TP
\fB-H\fP, \fB--with-filename\fP
-Force the inclusion of the filename at the start of output lines when searching
-a single file. By default, the filename is not shown in this case. For matching
-lines, the filename is followed by a colon; for context lines, a hyphen
-separator is used. If a line number is also being output, it follows the file
-name.
+Force the inclusion of the file name at the start of output lines when
+searching a single file. By default, the file name is not shown in this case.
+For matching lines, the file name is followed by a colon; for context lines, a
+hyphen separator is used. If a line number is also being output, it follows the
+file name. When the \fB-M\fP option causes a pattern to match more than one
+line, only the first is preceded by the file name.
.TP
\fB-h\fP, \fB--no-filename\fP
-Suppress the output filenames when searching multiple files. By default,
-filenames are shown when multiple files are searched. For matching lines, the
-filename is followed by a colon; for context lines, a hyphen separator is used.
+Suppress the output file names when searching multiple files. By default,
+file names are shown when multiple files are searched. For matching lines, the
+file name is followed by a colon; for context lines, a hyphen separator is used.
If a line number is also being output, it follows the file name.
.TP
\fB--help\fP
@@ -320,7 +327,7 @@
ignored.
.TP
\fB-I\fP
-Treat binary files as never matching. This is equivalent to
+Ignore binary files. This is equivalent to
\fB--binary-files\fP=\fIwithout-match\fP.
.TP
\fB-i\fP, \fB--ignore-case\fP
@@ -349,8 +356,8 @@
are processed are those that match one of the patterns (and do not match an
\fB--exclude-dir\fP pattern). This applies to all directories, whether listed
on the command line, obtained from \fB--file-list\fP, or by scanning a parent
-directory. The pattern is a PCRE2 regular expression, and is matched against the
-final component of the directory name, not the entire path. The \fB-F\fP,
+directory. The pattern is a PCRE2 regular expression, and is matched against
+the final component of the directory name, not the entire path. The \fB-F\fP,
\fB-w\fP, and \fB-x\fP options do not apply to this pattern. The option may be
given any number of times. If a directory matches both \fB--include-dir\fP and
\fB--exclude-dir\fP, it is excluded. There is no short form for this option.
@@ -381,8 +388,8 @@
is currently possible only in Unix-like environments). Output to terminal is
normally automatically flushed by the operating system. This option can be
useful when the input or output is attached to a pipe and you do not want
-\fBpcre2grep\fP to buffer up large amounts of data. However, its use will affect
-performance, and the \fB-M\fP (multiline) option ceases to work.
+\fBpcre2grep\fP to buffer up large amounts of data. However, its use will
+affect performance, and the \fB-M\fP (multiline) option ceases to work.
.TP
\fB--line-offsets\fP
Instead of showing lines or parts of lines that match, show each match as a
@@ -429,17 +436,31 @@
Allow patterns to match more than one line. When this option is given, patterns
may usefully contain literal newline characters and internal occurrences of ^
and $ characters. The output for a successful match may consist of more than
-one line, the last of which is the one in which the match ended. If the matched
-string ends with a newline sequence the output ends at the end of that line.
+one line. The first is the line in which the match started, and the last is the
+line in which the match ended. If the matched string ends with a newline
+sequence the output ends at the end of that line.
.sp
When this option is set, the PCRE2 library is called in "multiline" mode.
+However, \fBpcre2grep\fP still processes the input line by line. The difference
+is that a matched string may extend past the end of a line and continue on
+one or more subsequent lines. The newline sequence must be matched as part of
+the pattern. For example, to find the phrase "regular expression" in a file
+where "regular" might be at the end of a line and "expression" at the start of
+the next line, you could use this command:
+.sp
+ pcre2grep -M 'regular\es+expression' <file>
+.sp
+The \es escape sequence matches any white space character, including newlines,
+and is followed by + so as to match trailing white space on the first line as
+well as possibly handling a two-character newline sequence.
+.sp
There is a limit to the number of lines that can be matched, imposed by the way
that \fBpcre2grep\fP buffers the input file as it scans it. However,
-\fBpcre2grep\fP ensures that at least 8K characters or the rest of the document
+\fBpcre2grep\fP ensures that at least 8K characters or the rest of the file
(whichever is the shorter) are available for forward matching, and similarly
the previous 8K characters (or all the previous characters, if fewer than 8K)
-are guaranteed to be available for lookbehind assertions. This option does not
-work when input is read line by line (see \fP--line-buffered\fP.)
+are guaranteed to be available for lookbehind assertions. The \fB-M\fP option
+does not work when input is read line by line (see \fP--line-buffered\fP.)
.TP
\fB-N\fP \fInewline-type\fP, \fB--newline\fP=\fInewline-type\fP
The PCRE2 library supports five different conventions for indicating
@@ -455,9 +476,9 @@
This is normally the standard sequence for the operating system. Unless
otherwise specified by this option, \fBpcre2grep\fP uses the library's default.
The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This
-makes it possible to use \fBpcre2grep\fP to scan files that have come from other
-environments without having to modify their line endings. If the data that is
-being scanned does not agree with the convention set by this option,
+makes it possible to use \fBpcre2grep\fP to scan files that have come from
+other environments without having to modify their line endings. If the data
+that is being scanned does not agree with the convention set by this option,
\fBpcre2grep\fP may behave in strange ways. Note that this option does not
apply to files specified by the \fB-f\fP, \fB--exclude-from\fP, or
\fB--include-from\fP options, which are expected to use the operating system's
@@ -465,9 +486,10 @@
.TP
\fB-n\fP, \fB--line-number\fP
Precede each output line by its line number in the file, followed by a colon
-for matching lines or a hyphen for context lines. If the filename is also being
-output, it precedes the line number. This option is forced if
-\fB--line-offsets\fP is used.
+for matching lines or a hyphen for context lines. If the file name is also
+being output, it precedes the line number. When the \fB-M\fP option causes a
+pattern to match more than one line, only the first is preceded by its line
+number. This option is forced if \fB--line-offsets\fP is used.
.TP
\fB--no-jit\fP
If the PCRE2 library is built with support for just-in-time compiling (which
@@ -495,7 +517,7 @@
the same shell item, for example, -o3 or --only-matching=2. The comments given
for the non-argument case above also apply to this case. If the specified
capturing parentheses do not exist in the pattern, or were not set in the
-match, nothing is output unless the file name or line number are being printed.
+match, nothing is output unless the file name or line number are being output.
.sp
If this option is given multiple times, multiple substrings are output, in the
order the options are given. For example, -o3 -o1 -o3 causes the substrings
@@ -549,10 +571,10 @@
\fB-x\fP, \fB--line-regex\fP, \fB--line-regexp\fP
Force the patterns to be anchored (each must start matching at the beginning of
a line) and in addition, require them to match entire lines. This is equivalent
-to having ^ and $ characters at the start and end of each alternative branch in
-every pattern. This option applies only to the patterns that are matched
-against the contents of files; it does not apply to patterns specified by any
-of the \fB--include\fP or \fB--exclude\fP options.
+to having ^ and $ characters at the start and end of each alternative top-level
+branch in every pattern. This option applies only to the patterns that are
+matched against the contents of files; it does not apply to patterns specified
+by any of the \fB--include\fP or \fB--exclude\fP options.
.
.
.SH "ENVIRONMENT VARIABLES"
@@ -596,7 +618,7 @@
\fBpcre2grep\fP. For example, the \fB--include\fP option's argument is a glob
for GNU \fBgrep\fP, but a regular expression for \fBpcre2grep\fP. If both the
\fB-c\fP and \fB-l\fP options are given, GNU grep lists only file names,
-without counts, but \fBpcre2grep\fP gives the counts.
+without counts, but \fBpcre2grep\fP gives the counts as well.
.
.
.SH "OPTIONS WITH DATA"
@@ -642,9 +664,9 @@
message and the line that caused the problem to the standard error stream. If
there are more than 20 such errors, \fBpcre2grep\fP gives up.
.P
-The \fB--match-limit\fP option of \fBpcre2grep\fP can be used to set the overall
-resource limit; there is a second option called \fB--recursion-limit\fP that
-sets a limit on the amount of memory (usually stack) that is used (see the
+The \fB--match-limit\fP option of \fBpcre2grep\fP can be used to set the
+overall resource limit; there is a second option called \fB--recursion-limit\fP
+that sets a limit on the amount of memory (usually stack) that is used (see the
discussion of these options above).
.
.
@@ -661,7 +683,7 @@
.SH "SEE ALSO"
.rs
.sp
-\fBpcre2pattern\fP(3), \fBpcre2syntax\fP(3), \fBpcre2test\fP(1).
+\fBpcre2pattern\fP(3), \fBpcre2syntax\fP(3).
.
.
.SH AUTHOR
@@ -678,6 +700,6 @@
.rs
.sp
.nf
-Last updated: 23 November 2014
-Copyright (c) 1997-2014 University of Cambridge.
+Last updated: 03 January 2015
+Copyright (c) 1997-2015 University of Cambridge.
.fi
Modified: code/trunk/doc/pcre2grep.txt
===================================================================
--- code/trunk/doc/pcre2grep.txt 2015-01-02 17:09:16 UTC (rev 179)
+++ code/trunk/doc/pcre2grep.txt 2015-01-03 17:40:06 UTC (rev 180)
@@ -40,15 +40,15 @@
standard input can also be referenced by a name consisting of a single
hyphen. For example:
- pcre2grep some-pattern /file1 - /file3
+ pcre2grep some-pattern file1 - file3
- By default, each line that matches a pattern is copied to the standard
- output, and if there is more than one file, the file name is output at
- the start of each line, followed by a colon. However, there are options
- that can change how pcre2grep behaves. In particular, the -M option
- makes it possible to search for patterns that span line boundaries.
- What defines a line boundary is controlled by the -N (--newline)
- option.
+ Input files are searched line by line. By default, each line that
+ matches a pattern is copied to the standard output, and if there is
+ more than one file, the file name is output at the start of each line,
+ followed by a colon. However, there are options that can change how
+ pcre2grep behaves. In particular, the -M option makes it possible to
+ search for strings that span line boundaries. What defines a line
+ boundary is controlled by the -N (--newline) option.
The amount of memory used for buffering files that are being scanned is
controlled by a parameter that can be set by the --buffer-size option.
@@ -122,13 +122,13 @@
-- This terminates the list of options. It is useful if the next
item on the command line starts with a hyphen but is not an
- option. This allows for the processing of patterns and file-
+ option. This allows for the processing of patterns and file
names that start with hyphens.
-A number, --after-context=number
Output number lines of context after each matching line. If
- filenames and/or line numbers are being output, a hyphen sep-
- arator is used instead of a colon for the context lines. A
+ file names and/or line numbers are being output, a hyphen
+ separator is used instead of a colon for the context lines. A
line containing "--" is output between each group of lines,
unless they are in fact contiguous in the input file. The
value of number is expected to be relatively small. However,
@@ -141,8 +141,8 @@
-B number, --before-context=number
Output number lines of context before each matching line. If
- filenames and/or line numbers are being output, a hyphen sep-
- arator is used instead of a colon for the context lines. A
+ file names and/or line numbers are being output, a hyphen
+ separator is used instead of a colon for the context lines. A
line containing "--" is output between each group of lines,
unless they are in fact contiguous in the input file. The
value of number is expected to be relatively small. However,
@@ -160,249 +160,258 @@
which can have nasty effects if sent to a terminal. If the
word is "without-match", which is equivalent to the -I
option, binary files are not processed at all; they are
- assumed not to be of interest.
+ assumed not to be of interest and are skipped without causing
+ any output or affecting the return code.
--buffer-size=number
- Set the parameter that controls how much memory is used for
+ Set the parameter that controls how much memory is used for
buffering files that are being scanned.
-C number, --context=number
- Output number lines of context both before and after each
- matching line. This is equivalent to setting both -A and -B
+ Output number lines of context both before and after each
+ matching line. This is equivalent to setting both -A and -B
to the same value.
-c, --count
- Do not output individual lines from the files that are being
- scanned; instead output the number of lines that would other-
- wise have been shown. If no lines are selected, the number
- zero is output. If several files are are being scanned, a
- count is output for each of them. However, if the --files-
- with-matches option is also used, only those files whose
- counts are greater than zero are listed. When -c is used, the
- -A, -B, and -C options are ignored.
+ Do not output lines from the files that are being scanned;
+ instead output the number of matches (or non-matches if -v is
+ used) that would otherwise have caused lines to be shown. By
+ default, this count is the same as the number of suppressed
+ lines, but if the -M (multiline) option is used (without -v),
+ there may be more suppressed lines than the number of
+ matches.
+ If no lines are selected, the number zero is output. If sev-
+ eral files are are being scanned, a count is output for each
+ of them. However, if the --files-with-matches option is also
+ used, only those files whose counts are greater than zero are
+ listed. When -c is used, the -A, -B, and -C options are
+ ignored.
+
--colour, --color
If this option is given without any data, it is equivalent to
- "--colour=auto". If data is required, it must be given in
+ "--colour=auto". If data is required, it must be given in
the same shell item, separated by an equals sign.
--colour=value, --color=value
This option specifies under what circumstances the parts of a
line that matched a pattern should be coloured in the output.
- By default, the output is not coloured. The value (which is
- optional, see above) may be "never", "always", or "auto". In
- the latter case, colouring happens only if the standard out-
- put is connected to a terminal. More resources are used when
+ By default, the output is not coloured. The value (which is
+ optional, see above) may be "never", "always", or "auto". In
+ the latter case, colouring happens only if the standard out-
+ put is connected to a terminal. More resources are used when
colouring is enabled, because pcre2grep has to search for all
- possible matches in a line, not just one, in order to colour
+ possible matches in a line, not just one, in order to colour
them all.
The colour that is used can be specified by setting the envi-
- ronment variable PCRE2GREP_COLOUR or PCRE2GREP_COLOR. The
- value of this variable should be a string of two numbers,
- separated by a semicolon. They are copied directly into the
- control string for setting colour on a terminal, so it is
- your responsibility to ensure that they make sense. If nei-
- ther of the environment variables is set, the default is
+ ronment variable PCRE2GREP_COLOUR or PCRE2GREP_COLOR. The
+ value of this variable should be a string of two numbers,
+ separated by a semicolon. They are copied directly into the
+ control string for setting colour on a terminal, so it is
+ your responsibility to ensure that they make sense. If nei-
+ ther of the environment variables is set, the default is
"1;31", which gives red.
-D action, --devices=action
- If an input path is not a regular file or a directory,
- "action" specifies how it is to be processed. Valid values
+ If an input path is not a regular file or a directory,
+ "action" specifies how it is to be processed. Valid values
are "read" (the default) or "skip" (silently skip the path).
-d action, --directories=action
If an input path is a directory, "action" specifies how it is
- to be processed. Valid values are "read" (the default in
- non-Windows environments, for compatibility with GNU grep),
- "recurse" (equivalent to the -r option), or "skip" (silently
- skip the path, the default in Windows environments). In the
- "read" case, directories are read as if they were ordinary
- files. In some operating systems the effect of reading a
+ to be processed. Valid values are "read" (the default in
+ non-Windows environments, for compatibility with GNU grep),
+ "recurse" (equivalent to the -r option), or "skip" (silently
+ skip the path, the default in Windows environments). In the
+ "read" case, directories are read as if they were ordinary
+ files. In some operating systems the effect of reading a
directory like this is an immediate end-of-file; in others it
may provoke an error.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used mul-
tiple times in order to specify several patterns. It can also
- be used as a way of specifying a single pattern that starts
- with a hyphen. When -e is used, no argument pattern is taken
- from the command line; all arguments are treated as file
- names. There is no limit to the number of patterns. They are
- applied to each line in the order in which they are defined
+ be used as a way of specifying a single pattern that starts
+ with a hyphen. When -e is used, no argument pattern is taken
+ from the command line; all arguments are treated as file
+ names. There is no limit to the number of patterns. They are
+ applied to each line in the order in which they are defined
until one matches.
- If -f is used with -e, the command line patterns are matched
+ If -f is used with -e, the command line patterns are matched
first, followed by the patterns from the file(s), independent
- of the order in which these options are specified. Note that
- multiple use of -e is not the same as a single pattern with
+ of the order in which these options are specified. Note that
+ multiple use of -e is not the same as a single pattern with
alternatives. For example, X|Y finds the first character in a
- line that is X or Y, whereas if the two patterns are given
+ line that is X or Y, whereas if the two patterns are given
separately, with X first, pcre2grep finds X if it is present,
even if it follows Y in the line. It finds Y only if there is
- no X in the line. This matters only if you are using -o or
+ no X in the line. This matters only if you are using -o or
--colo(u)r to show the part(s) of the line that matched.
--exclude=pattern
Files (but not directories) whose names match the pattern are
- skipped without being processed. This applies to all files,
- whether listed on the command line, obtained from --file-
+ skipped without being processed. This applies to all files,
+ whether listed on the command line, obtained from --file-
list, or by scanning a directory. The pattern is a PCRE2 reg-
- ular expression, and is matched against the final component
- of the file name, not the entire path. The -F, -w, and -x
+ ular expression, and is matched against the final component
+ of the file name, not the entire path. The -F, -w, and -x
options do not apply to this pattern. The option may be given
any number of times in order to specify multiple patterns. If
- a file name matches both an --include and an --exclude pat-
+ a file name matches both an --include and an --exclude pat-
tern, it is excluded. There is no short form for this option.
--exclude-from=filename
- Treat each non-empty line of the file as the data for an
+ Treat each non-empty line of the file as the data for an
--exclude option. What constitutes a newline when reading the
- file is the operating system's default. The --newline option
- has no effect on this option. This option may be given more
+ file is the operating system's default. The --newline option
+ has no effect on this option. This option may be given more
than once in order to specify a number of files to read.
--exclude-dir=pattern
Directories whose names match the pattern are skipped without
- being processed, whatever the setting of the --recursive
- option. This applies to all directories, whether listed on
+ being processed, whatever the setting of the --recursive
+ option. This applies to all directories, whether listed on
the command line, obtained from --file-list, or by scanning a
- parent directory. The pattern is a PCRE2 regular expression,
- and is matched against the final component of the directory
- name, not the entire path. The -F, -w, and -x options do not
- apply to this pattern. The option may be given any number of
- times in order to specify more than one pattern. If a direc-
- tory matches both --include-dir and --exclude-dir, it is
+ parent directory. The pattern is a PCRE2 regular expression,
+ and is matched against the final component of the directory
+ name, not the entire path. The -F, -w, and -x options do not
+ apply to this pattern. The option may be given any number of
+ times in order to specify more than one pattern. If a direc-
+ tory matches both --include-dir and --exclude-dir, it is
excluded. There is no short form for this option.
-F, --fixed-strings
- Interpret each data-matching pattern as a list of fixed
- strings, separated by newlines, instead of as a regular
- expression. What constitutes a newline for this purpose is
- controlled by the --newline option. The -w (match as a word)
- and -x (match whole line) options can be used with -F. They
+ Interpret each data-matching pattern as a list of fixed
+ strings, separated by newlines, instead of as a regular
+ expression. What constitutes a newline for this purpose is
+ controlled by the --newline option. The -w (match as a word)
+ and -x (match whole line) options can be used with -F. They
apply to each of the fixed strings. A line is selected if any
of the fixed strings are found in it (subject to -w or -x, if
- present). This option applies only to the patterns that are
- matched against the contents of files; it does not apply to
- patterns specified by any of the --include or --exclude
+ present). This option applies only to the patterns that are
+ matched against the contents of files; it does not apply to
+ patterns specified by any of the --include or --exclude
options.
-f filename, --file=filename
- Read patterns from the file, one per line, and match them
- against each line of input. What constitutes a newline when
- reading the file is the operating system's default. The
+ Read patterns from the file, one per line, and match them
+ against each line of input. What constitutes a newline when
+ reading the file is the operating system's default. The
--newline option has no effect on this option. Trailing white
space is removed from each line, and blank lines are ignored.
- An empty file contains no patterns and therefore matches
+ An empty file contains no patterns and therefore matches
nothing. See also the comments about multiple patterns versus
- a single pattern with alternatives in the description of -e
+ a single pattern with alternatives in the description of -e
above.
- If this option is given more than once, all the specified
- files are read. A data line is output if any of the patterns
- match it. A filename can be given as "-" to refer to the
- standard input. When -f is used, patterns specified on the
- command line using -e may also be present; they are tested
- before the file's patterns. However, no other pattern is
+ If this option is given more than once, all the specified
+ files are read. A data line is output if any of the patterns
+ match it. A file name can be given as "-" to refer to the
+ standard input. When -f is used, patterns specified on the
+ command line using -e may also be present; they are tested
+ before the file's patterns. However, no other pattern is
taken from the command line; all arguments are treated as the
names of paths to be searched.
--file-list=filename
- Read a list of files and/or directories that are to be
- scanned from the given file, one per line. Trailing white
+ Read a list of files and/or directories that are to be
+ scanned from the given file, one per line. Trailing white
space is removed from each line, and blank lines are ignored.
- These paths are processed before any that are listed on the
- command line. The filename can be given as "-" to refer to
+ These paths are processed before any that are listed on the
+ command line. The file name can be given as "-" to refer to
the standard input. If --file and --file-list are both spec-
- ified as "-", patterns are read first. This is useful only
- when the standard input is a terminal, from which further
- lines (the list of files) can be read after an end-of-file
- indication. If this option is given more than once, all the
+ ified as "-", patterns are read first. This is useful only
+ when the standard input is a terminal, from which further
+ lines (the list of files) can be read after an end-of-file
+ indication. If this option is given more than once, all the
specified files are read.
--file-offsets
- Instead of showing lines or parts of lines that match, show
- each match as an offset from the start of the file and a
- length, separated by a comma. In this mode, no context is
- shown. That is, the -A, -B, and -C options are ignored. If
+ Instead of showing lines or parts of lines that match, show
+ each match as an offset from the start of the file and a
+ length, separated by a comma. In this mode, no context is
+ shown. That is, the -A, -B, and -C options are ignored. If
there is more than one match in a line, each of them is shown
- separately. This option is mutually exclusive with --line-
+ separately. This option is mutually exclusive with --line-
offsets and --only-matching.
-H, --with-filename
- Force the inclusion of the filename at the start of output
- lines when searching a single file. By default, the filename
- is not shown in this case. For matching lines, the filename
+ Force the inclusion of the file name at the start of output
+ lines when searching a single file. By default, the file name
+ is not shown in this case. For matching lines, the file name
is followed by a colon; for context lines, a hyphen separator
- is used. If a line number is also being output, it follows
- the file name.
+ is used. If a line number is also being output, it follows
+ the file name. When the -M option causes a pattern to match
+ more than one line, only the first is preceded by the file
+ name.
-h, --no-filename
- Suppress the output filenames when searching multiple files.
- By default, filenames are shown when multiple files are
- searched. For matching lines, the filename is followed by a
- colon; for context lines, a hyphen separator is used. If a
+ Suppress the output file names when searching multiple files.
+ By default, file names are shown when multiple files are
+ searched. For matching lines, the file name is followed by a
+ colon; for context lines, a hyphen separator is used. If a
line number is also being output, it follows the file name.
- --help Output a help message, giving brief details of the command
- options and file type support, and then exit. Anything else
+ --help Output a help message, giving brief details of the command
+ options and file type support, and then exit. Anything else
on the command line is ignored.
- -I Treat binary files as never matching. This is equivalent to
- --binary-files=without-match.
+ -I Ignore binary files. This is equivalent to --binary-
+ files=without-match.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
- If any --include patterns are specified, the only files that
- are processed are those that match one of the patterns (and
- do not match an --exclude pattern). This option does not
- affect directories, but it applies to all files, whether
- listed on the command line, obtained from --file-list, or by
- scanning a directory. The pattern is a PCRE2 regular expres-
- sion, and is matched against the final component of the file
- name, not the entire path. The -F, -w, and -x options do not
- apply to this pattern. The option may be given any number of
- times. If a file name matches both an --include and an
- --exclude pattern, it is excluded. There is no short form
+ If any --include patterns are specified, the only files that
+ are processed are those that match one of the patterns (and
+ do not match an --exclude pattern). This option does not
+ affect directories, but it applies to all files, whether
+ listed on the command line, obtained from --file-list, or by
+ scanning a directory. The pattern is a PCRE2 regular expres-
+ sion, and is matched against the final component of the file
+ name, not the entire path. The -F, -w, and -x options do not
+ apply to this pattern. The option may be given any number of
+ times. If a file name matches both an --include and an
+ --exclude pattern, it is excluded. There is no short form
for this option.
--include-from=filename
- Treat each non-empty line of the file as the data for an
+ Treat each non-empty line of the file as the data for an
--include option. What constitutes a newline for this purpose
- is the operating system's default. The --newline option has
+ is the operating system's default. The --newline option has
no effect on this option. This option may be given any number
of times; all the files are read.
--include-dir=pattern
- If any --include-dir patterns are specified, the only direc-
- tories that are processed are those that match one of the
- patterns (and do not match an --exclude-dir pattern). This
- applies to all directories, whether listed on the command
- line, obtained from --file-list, or by scanning a parent
- directory. The pattern is a PCRE2 regular expression, and is
- matched against the final component of the directory name,
- not the entire path. The -F, -w, and -x options do not apply
+ If any --include-dir patterns are specified, the only direc-
+ tories that are processed are those that match one of the
+ patterns (and do not match an --exclude-dir pattern). This
+ applies to all directories, whether listed on the command
+ line, obtained from --file-list, or by scanning a parent
+ directory. The pattern is a PCRE2 regular expression, and is
+ matched against the final component of the directory name,
+ not the entire path. The -F, -w, and -x options do not apply
to this pattern. The option may be given any number of times.
- If a directory matches both --include-dir and --exclude-dir,
+ If a directory matches both --include-dir and --exclude-dir,
it is excluded. There is no short form for this option.
-L, --files-without-match
- Instead of outputting lines from the files, just output the
- names of the files that do not contain any lines that would
- have been output. Each file name is output once, on a sepa-
+ Instead of outputting lines from the files, just output the
+ names of the files that do not contain any lines that would
+ have been output. Each file name is output once, on a sepa-
rate line.
-l, --files-with-matches
- Instead of outputting lines from the files, just output the
+ Instead of outputting lines from the files, just output the
names of the files containing lines that would have been out-
- put. Each file name is output once, on a separate line.
- Searching normally stops as soon as a matching line is found
- in a file. However, if the -c (count) option is also used,
- matching continues in order to obtain the correct count, and
- those files that have at least one match are listed along
+ put. Each file name is output once, on a separate line.
+ Searching normally stops as soon as a matching line is found
+ in a file. However, if the -c (count) option is also used,
+ matching continues in order to obtain the correct count, and
+ those files that have at least one match are listed along
with their counts. Using this option with -c is a way of sup-
pressing the listing of files with no matches.
@@ -412,87 +421,104 @@
input)" is used. There is no short form for this option.
--line-buffered
- When this option is given, input is read and processed line
- by line, and the output is flushed after each write. By
- default, input is read in large chunks, unless pcre2grep can
- determine that it is reading from a terminal (which is cur-
- rently possible only in Unix-like environments). Output to
- terminal is normally automatically flushed by the operating
+ When this option is given, input is read and processed line
+ by line, and the output is flushed after each write. By
+ default, input is read in large chunks, unless pcre2grep can
+ determine that it is reading from a terminal (which is cur-
+ rently possible only in Unix-like environments). Output to
+ terminal is normally automatically flushed by the operating
system. This option can be useful when the input or output is
attached to a pipe and you do not want pcre2grep to buffer up
- large amounts of data. However, its use will affect perfor-
+ large amounts of data. However, its use will affect perfor-
mance, and the -M (multiline) option ceases to work.
--line-offsets
- Instead of showing lines or parts of lines that match, show
+ Instead of showing lines or parts of lines that match, show
each match as a line number, the offset from the start of the
- line, and a length. The line number is terminated by a colon
- (as usual; see the -n option), and the offset and length are
- separated by a comma. In this mode, no context is shown.
- That is, the -A, -B, and -C options are ignored. If there is
- more than one match in a line, each of them is shown sepa-
+ line, and a length. The line number is terminated by a colon
+ (as usual; see the -n option), and the offset and length are
+ separated by a comma. In this mode, no context is shown.
+ That is, the -A, -B, and -C options are ignored. If there is
+ more than one match in a line, each of them is shown sepa-
rately. This option is mutually exclusive with --file-offsets
and --only-matching.
--locale=locale-name
- This option specifies a locale to be used for pattern match-
- ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
- ronment variables. If no locale is specified, the PCRE2
- library's default (usually the "C" locale) is used. There is
+ This option specifies a locale to be used for pattern match-
+ ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
+ ronment variables. If no locale is specified, the PCRE2
+ library's default (usually the "C" locale) is used. There is
no short form for this option.
--match-limit=number
- Processing some regular expression patterns can require a
- very large amount of memory, leading in some cases to a pro-
- gram crash if not enough is available. Other patterns may
- take a very long time to search for all possible matching
- strings. The pcre2_match() function that is called by
- pcre2grep to do the matching has two parameters that can
+ Processing some regular expression patterns can require a
+ very large amount of memory, leading in some cases to a pro-
+ gram crash if not enough is available. Other patterns may
+ take a very long time to search for all possible matching
+ strings. The pcre2_match() function that is called by
+ pcre2grep to do the matching has two parameters that can
limit the resources that it uses.
- The --match-limit option provides a means of limiting
+ The --match-limit option provides a means of limiting
resource usage when processing patterns that are not going to
match, but which have a very large number of possibilities in
- their search trees. The classic example is a pattern that
+ their search trees. The classic example is a pattern that
uses nested unlimited repeats. Internally, PCRE2 uses a func-
- tion called match() which it calls repeatedly (sometimes
- recursively). The limit set by --match-limit is imposed on
- the number of times this function is called during a match,
- which has the effect of limiting the amount of backtracking
+ tion called match() which it calls repeatedly (sometimes
+ recursively). The limit set by --match-limit is imposed on
+ the number of times this function is called during a match,
+ which has the effect of limiting the amount of backtracking
that can take place.
The --recursion-limit option is similar to --match-limit, but
instead of limiting the total number of times that match() is
called, it limits the depth of recursive calls, which in turn
- limits the amount of memory that can be used. The recursion
- depth is a smaller number than the total number of calls,
+ limits the amount of memory that can be used. The recursion
+ depth is a smaller number than the total number of calls,
because not all calls to match() are recursive. This limit is
of use only if it is set smaller than --match-limit.
- There are no short forms for these options. The default set-
- tings are specified when the PCRE2 library is compiled, with
+ There are no short forms for these options. The default set-
+ tings are specified when the PCRE2 library is compiled, with
the default default being 10 million.
-M, --multiline
- Allow patterns to match more than one line. When this option
+ Allow patterns to match more than one line. When this option
is given, patterns may usefully contain literal newline char-
- acters and internal occurrences of ^ and $ characters. The
- output for a successful match may consist of more than one
- line, the last of which is the one in which the match ended.
- If the matched string ends with a newline sequence the output
- ends at the end of that line.
+ acters and internal occurrences of ^ and $ characters. The
+ output for a successful match may consist of more than one
+ line. The first is the line in which the match started, and
+ the last is the line in which the match ended. If the matched
+ string ends with a newline sequence the output ends at the
+ end of that line.
When this option is set, the PCRE2 library is called in "mul-
- tiline" mode. There is a limit to the number of lines that
- can be matched, imposed by the way that pcre2grep buffers the
- input file as it scans it. However, pcre2grep ensures that at
- least 8K characters or the rest of the document (whichever is
- the shorter) are available for forward matching, and simi-
- larly the previous 8K characters (or all the previous charac-
- ters, if fewer than 8K) are guaranteed to be available for
- lookbehind assertions. This option does not work when input
- is read line by line (see --line-buffered.)
+ tiline" mode. However, pcre2grep still processes the input
+ line by line. The difference is that a matched string may
+ extend past the end of a line and continue on one or more
+ subsequent lines. The newline sequence must be matched as
+ part of the pattern. For example, to find the phrase "regular
+ expression" in a file where "regular" might be at the end of
+ a line and "expression" at the start of the next line, you
+ could use this command:
+ pcre2grep -M 'regular\s+expression' <file>
+
+ The \s escape sequence matches any white space character,
+ including newlines, and is followed by + so as to match
+ trailing white space on the first line as well as possibly
+ handling a two-character newline sequence.
+
+ There is a limit to the number of lines that can be matched,
+ imposed by the way that pcre2grep buffers the input file as
+ it scans it. However, pcre2grep ensures that at least 8K
+ characters or the rest of the file (whichever is the shorter)
+ are available for forward matching, and similarly the previ-
+ ous 8K characters (or all the previous characters, if fewer
+ than 8K) are guaranteed to be available for lookbehind asser-
+ tions. The -M option does not work when input is read line by
+ line (see --line-buffered.)
+
-N newline-type, --newline=newline-type
The PCRE2 library supports five different conventions for
indicating the ends of lines. They are the single-character
@@ -522,8 +548,10 @@
-n, --line-number
Precede each output line by its line number in the file, fol-
lowed by a colon for matching lines or a hyphen for context
- lines. If the filename is also being output, it precedes the
- line number. This option is forced if --line-offsets is used.
+ lines. If the file name is also being output, it precedes the
+ line number. When the -M option causes a pattern to match
+ more than one line, only the first is preceded by its line
+ number. This option is forced if --line-offsets is used.
--no-jit If the PCRE2 library is built with support for just-in-time
compiling (which speeds up matching), pcre2grep automatically
@@ -555,8 +583,8 @@
The comments given for the non-argument case above also apply
to this case. If the specified capturing parentheses do not
exist in the pattern, or were not set in the match, nothing
- is output unless the file name or line number are being
- printed.
+ is output unless the file name or line number are being out-
+ put.
If this option is given multiple times, multiple substrings
are output, in the order the options are given. For example,
@@ -617,11 +645,11 @@
Force the patterns to be anchored (each must start matching
at the beginning of a line) and in addition, require them to
match entire lines. This is equivalent to having ^ and $
- characters at the start and end of each alternative branch in
- every pattern. This option applies only to the patterns that
- are matched against the contents of files; it does not apply
- to patterns specified by any of the --include or --exclude
- options.
+ characters at the start and end of each alternative top-level
+ branch in every pattern. This option applies only to the pat-
+ terns that are matched against the contents of files; it does
+ not apply to patterns specified by any of the --include or
+ --exclude options.
ENVIRONMENT VARIABLES
@@ -662,7 +690,7 @@
ferent in pcre2grep. For example, the --include option's argument is a
glob for GNU grep, but a regular expression for pcre2grep. If both the
-c and -l options are given, GNU grep lists only file names, without
- counts, but pcre2grep gives the counts.
+ counts, but pcre2grep gives the counts as well.
OPTIONS WITH DATA
@@ -725,7 +753,7 @@
SEE ALSO
- pcre2pattern(3), pcre2syntax(3), pcre2test(1).
+ pcre2pattern(3), pcre2syntax(3).
AUTHOR
@@ -737,5 +765,5 @@
REVISION
- Last updated: 23 November 2014
- Copyright (c) 1997-2014 University of Cambridge.
+ Last updated: 03 January 2015
+ Copyright (c) 1997-2015 University of Cambridge.
