pcregrep 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
pcrepattern
for a full description of syntax and semantics of the regular expressions that
PCRE supports.
Patterns, whether supplied on the command line or in a separate file, are given
without delimiters. For example:
pcregrep Thursday /etc/motd
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 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.
The first argument that follows any option settings is treated as the single
pattern to be matched when neither -e nor -f 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 -e, -f, or an
argument pattern must be provided.
If no files are specified, pcregrep reads the standard input. The
standard input can also be referenced by a name consisting of a single hyphen.
For example:
pcregrep some-pattern /file1 - /file3
By default, each line that matches the 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. However, there are options that can change how
pcregrep behaves. In particular, the -M option makes it possible to
search for patterns that span line boundaries.
Patterns are limited to 8K or BUFSIZ characters, whichever is the greater.
BUFSIZ is defined in <stdio.h>.
If the LC_ALL or LC_CTYPE environment variable is set,
pcregrep uses the value to set a locale when calling the PCRE library.
The --locale option can be used to override this.
OPTIONS
--
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.
-Anumber, --after-context=number
Output number 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 number is expected to be relatively small. However, pcregrep
guarantees to have up to 8K of following text available for context output.
-Bnumber, --before-context=number
Output number 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 number is expected to be relatively small. However, pcregrep
guarantees to have up to 8K of preceding text available for context output.
-Cnumber, --context=number
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; 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 -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 the same shell item, separated by an
equals sign.
--colour=value, --color=value
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.
-Daction, --devices=action
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).
-daction, --directories=action
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 -r
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.
-epattern, --regex=pattern,
--regexp=pattern 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
-e 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 -v is used). If -f is used
with -e, 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 -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 separately,
pcregrep 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 -o to show the portion of the line that matched.
--exclude=pattern
When pcregrep is searching the files in a directory as a consequence of
the -r (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 --include and --exclude, it is excluded. There is no short
form for this option.
-F, --fixed-strings
Interpret each pattern as a list of fixed strings, separated by newlines,
instead of as a regular expression. 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).
-ffilename, --file=filename
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 -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 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.
-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 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.
-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 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.
--help
Output a brief help message and exit.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
When pcregrep is searching the files in a directory as a consequence of
the -r (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 --include and --exclude, 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 separate line.
-l, --files-with-matches
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.
--label=name
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.
--locale=locale-name
This option specifies a locale to be used for pattern matching. It overrides
the value in the LC_ALL or LC_CTYPE 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.
-M, --multiline
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 pcregrep buffers the input file as it scans it. However,
pcregrep 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.
-n, --line-number
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.
-o, --only-matching
Show only the part of the line that matched a pattern. In this mode, no
context is shown. That is, the -A, -B, and -C options are
ignored.
-q, --quiet
Work quietly, that is, display nothing except error messages. The exit
status indicates whether or not any matches were found.
-r, --recursive
If any given path is a directory, recursively scan the files it contains,
taking note of any --include and --exclude 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 -d
option to "recurse".
-s, --no-messages
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.
-u, --utf-8
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.
-V, --version
Write the version numbers of pcregrep and the PCRE library that is being
used to the standard error stream.
-v, --invert-match
Invert the sense of the match, so that lines which do not match any of
the patterns are the ones that are found.
-w, --word-regex, --word-regexp
Force the patterns to match only whole words. This is equivalent to having \b
at the start and end of the pattern.
-x, --line-regex, --line-regexp
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.
ENVIRONMENT VARIABLES
The environment variables LC_ALL and LC_CTYPE are examined, in that
order, for a locale. The first one that is set is used. This can be overridden
by the --locale option. If no locale is set, the PCRE library's default
(usually the "C" locale) is used.
OPTIONS COMPATIBILITY
The majority of short and long forms of pcregrep's options are the same
as in the GNU grep program. Any long option of the form
--xxx-regexp (GNU terminology) is also available as --xxx-regex
(PCRE terminology). However, the --locale, -M, --multiline,
-u, and --utf-8 options are specific to pcregrep.
OPTIONS WITH DATA
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:
-f/some/file
-f /some/file
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:
--file=/some/file
--file /some/file
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.
The exception to the above is the --colour (or --color) 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.
MATCHING ERRORS
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+)*\d 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, pcregrep outputs an error
message and the line that caused the problem to the standard error stream. If
there are more than 20 such errors, pcregrep gives up.
DIAGNOSTICS
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 -s option to
suppress error messages about inaccessble files does not affect the return
code.
AUTHOR
Philip Hazel
University Computing Service
Cambridge CB2 3QG, England.
Last updated: 23 January 2006
Copyright (c) 1997-2006 University of Cambridge.
