pcregrep
PCREGREP(1) PCREGREP(1)
NAME
pcregrep - a grep with Perl-compatible regular expressions.
SYNOPSIS
pcregrep [options] [long options] [pattern] [path1 path2 ...]
DESCRIPTION
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(3) 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 pat-
tern 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. Con-
versely, when one or both of these options are used to specify pat-
terns, 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 stan-
dard output, and if there is more than one file, the file name is out-
put 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. What
defines a line boundary is controlled by the -N (--newline) option.
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 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
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. How-
ever, pcregrep guarantees to have up to 8K of following text
available for context output.
-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
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. How-
ever, pcregrep guarantees to have up to 8K of preceding text
available for context output.
-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
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 out-
put. 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 out-
put. 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 PCRE-
GREP_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 vari-
ables 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
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),
"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.
-e pattern, --regex=pattern,
--regexp=pattern Specify a pattern to be matched. This
option can be used multiple times in order to specify sev-
eral 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).
-f filename, --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, pat-
terns specified on the command line using -e may also be
present; they are tested before the file’s patterns. How-
ever, 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 pat-
tern 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 sepa-
rate 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 match-
ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
ronment 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 docu-
ment (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 newline-type, --newline=newline-type
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 rec-
ognizes any of the preceding three types, and an "any" con-
vention, 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 (form-
feed, U+000C), NEL (next line, U+0085), LS (line separator,
U+2028), and PS (paragraph separator, U+2029).
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 speci-
fied by this option, pcregrep uses the library’s default.
The possible values for this option are CR, LF, CRLF,
ANYCRLF, or ANY. This makes it possible to use pcregrep 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, pcregrep may behave in strange ways.
-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 mes-
sages. 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 set-
tings. 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 sub-
ject 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 equiv-
alent 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.
NEWLINES
The -N (--newline) option allows pcregrep to scan files with different
newline conventions from the default. However, the setting of this
option does not affect the way in which pcregrep writes information to
the standard error and output streams. It uses the string "\n" in C
printf() 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.
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 termi-
nology). 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 imme-
diately, 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 inaccess-
ble files does not affect the return code.
SEE ALSO
pcrepattern(3), pcretest(1).
AUTHOR
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
REVISION
Last updated: 16 April 2007
Copyright (c) 1997-2007 University of Cambridge.
PCREGREP(1)
