trunk/doc/pcregrep.1

.TH PCREGREP 1
.SH NAME
pcregrep - a grep with Perl-compatible regular expressions.
.SH SYNOPSIS
.B pcregrep [options] [long options] [pattern] [path1 path2 ...]
.
.SH DESCRIPTION
.rs
.sp
\fBpcregrep\fP searches files for character patterns, in the same way as other
grep commands do, but it uses the PCRE regular expression library to support
patterns that are compatible with the regular expressions of Perl 5. See
.\" HREF
\fBpcrepattern\fP(3)
.\"
for a full description of syntax and semantics of the regular expressions
that PCRE supports.
.P
Patterns, whether supplied on the command line or in a separate file, are given
without delimiters. For example:
.sp
  pcregrep Thursday /etc/motd
.sp
If you attempt to use delimiters (for example, by surrounding a pattern with
slashes, as is common in Perl scripts), they are interpreted as part of the
pattern. Quotes can of course be used to delimit patterns on the command line
because they are interpreted by the shell, and indeed they are required if a
pattern contains white space or shell metacharacters.
.P
The first argument that follows any option settings is treated as the single
pattern to be matched when neither \fB-e\fP nor \fB-f\fP is present.
Conversely, when one or both of these options are used to specify patterns, all
arguments are treated as path names. At least one of \fB-e\fP, \fB-f\fP, or an
argument pattern must be provided.
.P
If no files are specified, \fBpcregrep\fP reads the standard input. The
standard input can also be referenced by a name consisting of a single hyphen.
For example:
.sp
  pcregrep 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 \fBpcregrep\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.
.P
Patterns are limited to 8K or BUFSIZ characters, whichever is the greater.
BUFSIZ is defined in \fB<stdio.h>\fP. When there is more than one pattern 
(specified by the use of \fB-e\fP and/or \fB-f\fP), each pattern is applied to 
each line in the order in which they are defined, except that all the \fB-e\fP 
patterns are tried before the \fB-f\fP patterns. As soon as one pattern matches 
(or fails to match when \fB-v\fP is used), no further patterns are considered.
.P
When \fB--only-matching\fP, \fB--file-offsets\fP, or \fB--line-offsets\fP
is used, the output is the part of the line that matched (either shown
literally, or as an offset). In this case, scanning resumes immediately
following the match, so that further matches on the same line can be found.
If there are multiple patterns, they are all tried on the remainder of the 
line. However, patterns that follow the one that matched are not tried on the 
earlier part of the line.
.P
If the \fBLC_ALL\fP or \fBLC_CTYPE\fP environment variable is set,
\fBpcregrep\fP uses the value to set a locale when calling the PCRE library.
The \fB--locale\fP option can be used to override this.
.
.SH OPTIONS
.rs
.TP 10
\fB--\fP
This terminate 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.
.TP
\fB-A\fP \fInumber\fP, \fB--after-context=\fP\fInumber\fP
Output \fInumber\fP lines of context after each matching line. If filenames
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 \fInumber\fP is expected to be relatively small. However, \fBpcregrep\fP
guarantees to have up to 8K of following text available for context output.
.TP
\fB-B\fP \fInumber\fP, \fB--before-context=\fP\fInumber\fP
Output \fInumber\fP lines of context before each matching line. If filenames
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 \fInumber\fP is expected to be relatively small. However, \fBpcregrep\fP
guarantees to have up to 8K of preceding text available for context output.
.TP
\fB-C\fP \fInumber\fP, \fB--context=\fP\fInumber\fP
Output \fInumber\fP lines of context both before and after each matching line.
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; instead just output a count of the number of
lines that would otherwise have been output. If several files are given, a
count is output for each of them. In this mode, the \fB-A\fP, \fB-B\fP, and
\fB-C\fP options are ignored.
.TP
\fB--colour\fP, \fB--color\fP
If this option is given without any data, it is equivalent to "--colour=auto".
If data is required, it must be given in the same shell item, separated by an
equals sign.
.TP
\fB--colour=\fP\fIvalue\fP, \fB--color=\fP\fIvalue\fP
This option specifies under what circumstances the part of a line that matched
a pattern should be coloured in the output. The value may be "never" (the
default), "always", or "auto". In the latter case, colouring happens only if
the standard output is connected to a terminal. The colour can be specified by
setting the environment variable PCREGREP_COLOUR or PCREGREP_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
neither of the environment variables is set, the default is "1;31", which gives
red.
.TP
\fB-D\fP \fIaction\fP, \fB--devices=\fP\fIaction\fP
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).
.TP
\fB-d\fP \fIaction\fP, \fB--directories=\fP\fIaction\fP
If an input path is a directory, "action" specifies how it is to be processed.
Valid values are "read" (the default), "recurse" (equivalent to the \fB-r\fP
option), or "skip" (silently skip the path). In the default 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.
.TP
\fB-e\fP \fIpattern\fP, \fB--regex=\fP\fIpattern\fP, \fB--regexp=\fP\fIpattern\fP 
Specify a pattern to be matched. This option can be used multiple 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 \fB-e\fP is used, no argument
pattern is taken from the command line; all arguments are treated as file
names. There is an overall maximum of 100 patterns. They are applied to each
line in the order in which they are defined until one matches (or fails to
match if \fB-v\fP is used). If \fB-f\fP is used with \fB-e\fP, the command line
patterns are matched first, followed by the patterns from the file, independent
of the order in which these options are specified. Note that multiple use of
\fB-e\fP 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 separately, \fBpcregrep\fP 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
really matters only if you are using \fB-o\fP to show the part(s) of the line
that matched.
.TP
\fB--exclude\fP=\fIpattern\fP
When \fBpcregrep\fP is searching the files in a directory as a consequence of
the \fB-r\fP (recursive search) option, any files whose names match the pattern
are excluded. The pattern is a PCRE regular expression. If a file name matches
both \fB--include\fP and \fB--exclude\fP, it is excluded. There is no short
form for this option.
.TP
\fB-F\fP, \fB--fixed-strings\fP
Interpret each pattern as a list of fixed strings, separated by newlines,
instead of as a regular expression. The \fB-w\fP (match as a word) and \fB-x\fP
(match whole line) options can be used with \fB-F\fP. They apply to each of the
fixed strings. A line is selected if any of the fixed strings are found in it
(subject to \fB-w\fP or \fB-x\fP, if present).
.TP
\fB-f\fP \fIfilename\fP, \fB--file=\fP\fIfilename\fP
Read a number of patterns from the file, one per line, and match them against
each line of input. A data line is output if any of the patterns match it. The
filename 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 command line; all arguments are treated as file names. There
is an overall maximum of 100 patterns. Trailing white space is removed from
each line, and blank lines are ignored. 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 \fB-e\fP above.
.TP
\fB--file-offsets\fP
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 \fB-A\fP, \fB-B\fP, and \fB-C\fP
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 \fB--line-offsets\fP
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 and a space; for context lines, a
hyphen separator is used. If a line number is also being output, it follows the
file name without a space.
.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 and a space; for context lines, a hyphen
separator is used. If a line number is also being output, it follows the file
name without a space.
.TP
\fB--help\fP
Output a brief help message and exit.
.TP
\fB-i\fP, \fB--ignore-case\fP
Ignore upper/lower case distinctions during comparisons.
.TP
\fB--include\fP=\fIpattern\fP
When \fBpcregrep\fP is searching the files in a directory as a consequence of
the \fB-r\fP (recursive search) option, only those files whose names match the
pattern are included. The pattern is a PCRE regular expression. If a file name
matches both \fB--include\fP and \fB--exclude\fP, it is excluded. There is no
short form for this option.
.TP
\fB-L\fP, \fB--files-without-match\fP
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 separate line.
.TP
\fB-l\fP, \fB--files-with-matches\fP
Instead of outputting lines from the files, just output the names of the files
containing lines that would have been output. Each file name is output
once, on a separate line. Searching stops as soon as a matching line is found
in a file.
.TP
\fB--label\fP=\fIname\fP
This option supplies a name to be used for the standard input when file names
are being output. If not supplied, "(standard input)" is used. There is no
short form for this option.
.TP
\fB--line-offsets\fP
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 \fB-n\fP option), and the 
offset and length are separated by a comma. In this mode, no context is shown.
That is, the \fB-A\fP, \fB-B\fP, and \fB-C\fP 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 \fB--file-offsets\fP and \fB--only-matching\fP.
.TP
\fB--locale\fP=\fIlocale-name\fP
This option specifies a locale to be used for pattern matching. It overrides
the value in the \fBLC_ALL\fP or \fBLC_CTYPE\fP environment variables. If no
locale is specified, the PCRE library's default (usually the "C" locale) is
used. There is no short form for this option.
.TP
\fB-M\fP, \fB--multiline\fP
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 any one match may consist of more than one
line. When this option is set, the PCRE library is called in "multiline" mode.
There is a limit to the number of lines that can be matched, imposed by the way
that \fBpcregrep\fP buffers the input file as it scans it. However,
\fBpcregrep\fP ensures that at least 8K characters or the rest of the document
(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.
.TP
\fB-N\fP \fInewline-type\fP, \fB--newline=\fP\fInewline-type\fP
The PCRE library supports five different conventions for indicating
the ends of lines. They are the single-character sequences CR (carriage return)
and LF (linefeed), the two-character sequence CRLF, an "anycrlf" convention,
which recognizes any of the preceding three types, and an "any" convention, in
which any Unicode line ending sequence is assumed to end a line. The Unicode
sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF
(formfeed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and
PS (paragraph separator, U+2029).
.sp
When the PCRE library is built, a default line-ending sequence is specified.
This is normally the standard sequence for the operating system. Unless
otherwise specified by this option, \fBpcregrep\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 \fBpcregrep\fP on 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,
\fBpcregrep\fP may behave in strange ways.
.TP
\fB-n\fP, \fB--line-number\fP
Precede each output line by its line number in the file, followed by a colon
and a space for matching lines or a hyphen and a space 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.
.TP
\fB-o\fP, \fB--only-matching\fP
Show only the part of the line that matched a pattern. In this mode, no
context is shown. That is, the \fB-A\fP, \fB-B\fP, and \fB-C\fP options are
ignored. If there is more than one match in a line, each of them is shown 
separately. If \fB-o\fP is combined with \fB-v\fP (invert the sense of the 
match to find non-matching lines), no output is generated, but the return code 
is set appropriately. This option is mutually exclusive with 
\fB--file-offsets\fP and \fB--line-offsets\fP.
.TP
\fB-q\fP, \fB--quiet\fP
Work quietly, that is, display nothing except error messages. The exit
status indicates whether or not any matches were found.
.TP
\fB-r\fP, \fB--recursive\fP
If any given path is a directory, recursively scan the files it contains,
taking note of any \fB--include\fP and \fB--exclude\fP settings. By default, a
directory is read as a normal file; in some operating systems this gives an
immediate end-of-file. This option is a shorthand for setting the \fB-d\fP
option to "recurse".
.TP
\fB-s\fP, \fB--no-messages\fP
Suppress error messages about non-existent or unreadable files. Such files are
quietly skipped. However, the return code is still 2, even if matches were
found in other files.
.TP
\fB-u\fP, \fB--utf-8\fP
Operate in UTF-8 mode. This option is available only if PCRE has been compiled
with UTF-8 support. Both patterns and subject lines must be valid strings of
UTF-8 characters.
.TP
\fB-V\fP, \fB--version\fP
Write the version numbers of \fBpcregrep\fP and the PCRE library that is being
used to the standard error stream.
.TP
\fB-v\fP, \fB--invert-match\fP
Invert the sense of the match, so that lines which do \fInot\fP match any of
the patterns are the ones that are found.
.TP
\fB-w\fP, \fB--word-regex\fP, \fB--word-regexp\fP
Force the patterns to match only whole words. This is equivalent to having \eb
at the start and end of the pattern.
.TP
\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.
.
.
.SH "ENVIRONMENT VARIABLES"
.rs
.sp
The environment variables \fBLC_ALL\fP and \fBLC_CTYPE\fP are examined, in that
order, for a locale. The first one that is set is used. This can be overridden
by the \fB--locale\fP option. If no locale is set, the PCRE library's default
(usually the "C" locale) is used.
.
.
.SH "NEWLINES"
.rs
.sp
The \fB-N\fP (\fB--newline\fP) option allows \fBpcregrep\fP to scan files with
different newline conventions from the default. However, the setting of this
option does not affect the way in which \fBpcregrep\fP writes information to
the standard error and output streams. It uses the string "\en" in C
\fBprintf()\fP calls to indicate newlines, relying on the C I/O library to
convert this to an appropriate sequence if the output is sent to a file.
.
.
.SH "OPTIONS COMPATIBILITY"
.rs
.sp
The majority of short and long forms of \fBpcregrep\fP's options are the same
as in the GNU \fBgrep\fP program. Any long option of the form
\fB--xxx-regexp\fP (GNU terminology) is also available as \fB--xxx-regex\fP
(PCRE terminology). However, the \fB--locale\fP, \fB-M\fP, \fB--multiline\fP,
\fB-u\fP, and \fB--utf-8\fP options are specific to \fBpcregrep\fP.
.
.
.SH "OPTIONS WITH DATA"
.rs
.sp
There are four different ways in which an option with data can be specified.
If a short form option is used, the data may follow immediately, or in the next
command line item. For example:
.sp
  -f/some/file
  -f /some/file
.sp
If a long form option is used, the data may appear in the same command line
item, separated by an equals character, or (with one exception) it may appear
in the next command line item. For example:
.sp
  --file=/some/file
  --file /some/file
.sp
Note, however, that if you want to supply a file name beginning with ~ as data
in a shell command, and have the shell expand ~ to a home directory, you must
separate the file name from the option, because the shell does not treat ~
specially unless it is at the start of an item.
.P
The exception to the above is the \fB--colour\fP (or \fB--color\fP) option,
for which the data is optional. If this option does have data, it must be given
in the first form, using an equals character. Otherwise it will be assumed that
it has no data.
.
.
.SH "MATCHING ERRORS"
.rs
.sp
It is possible to supply a regular expression that takes a very long time to
fail to match certain lines. Such patterns normally involve nested indefinite
repeats, for example: (a+)*\ed when matched against a line of a's with no final
digit. The PCRE matching function has a resource limit that causes it to abort
in these circumstances. If this happens, \fBpcregrep\fP outputs an error
message and the line that caused the problem to the standard error stream. If
there are more than 20 such errors, \fBpcregrep\fP gives up.
.
.
.SH DIAGNOSTICS
.rs
.sp
Exit status is 0 if any matches were found, 1 if no matches were found, and 2
for syntax errors and non-existent or inacessible files (even if matches were
found in other files) or too many matching errors. Using the \fB-s\fP option to
suppress error messages about inaccessble files does not affect the return
code.
.
.
.SH "SEE ALSO"
.rs
.sp
\fBpcrepattern\fP(3), \fBpcretest\fP(1).
.
.
.SH AUTHOR
.rs
.sp
.nf
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
.fi
.
.
.SH REVISION
.rs
.sp
.nf
Last updated: 07 December 2007
Copyright (c) 1997-2007 University of Cambridge.
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