| |
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 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. 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 stan-
dard 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 pos-
sible to search for patterns that span line boundaries.
Patterns are limited to 8K or BUFSIZ characters, whichever is the
greater. BUFSIZ is defined in .
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 sep-
arator 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 avail-
able 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 sep-
arator 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 avail-
able 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 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 speci-
fied 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 ter-
minal, 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.
-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 several pat-
terns. It can also be used as a way of specifying a single
pattern that starts with a hyphen. When -e is used, no argu-
ment 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 speci-
fied. Note that multiple use of -e is not the same as a sin-
gle 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 con-
sequence 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 (sub-
ject 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, 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 out-
put, 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 con-
sequence 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 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 out-
put. 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 char-
acters 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 "mul-
tiline" 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 simi-
larly the previous 8K characters (or all the previous charac-
ters, 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, fol-
lowed 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 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 equiva-
lent 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 spec-
ified. If a short form option is used, the data may follow immedi-
ately, 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.
PCREGREP(1)
|