pcregrep — a grep with Perl-compatible regular expressions.
pcregrep
[options] [ long
options ] [pattern] [ path1 path2... ]
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 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.
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 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
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
>
When there is more than one pattern (specified by the use of
−e
and/or −f
), each pattern is applied to each
line in the order in which they are defined, except that all
the −e
patterns are tried
before the −f
patterns. As
soon as one pattern matches (or fails to match when
−v
is used), no further
patterns are considered.
When −−only−matching
,
−−file−offsets
,
or −−line−offsets
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.
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.
It is possible to compile pcregrep so that it uses
libz or
libbz2 to read
files whose names end in .gz
or .bz2
, respectively. You can
find out whether your binary has support for one or both of
these file types by running it with the −−help
option. If the appropriate
support is not present, files are treated as plain text. The
standard input is always so treated.
−−
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.
−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. However, 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. However, 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 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.
−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
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 part(s) 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, 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. See also the comments about
multiple patterns versus a single pattern with
alternatives in the description of −e
above.
−−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 there
is more than one match in a line, each of them is shown
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 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 help message, giving brief details of the command options and file type support, and then 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.
−−line−offsets
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
separately. This option is mutually exclusive with
−−file−offsets
and
−−only−matching
.
−−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
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 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).
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, 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. This option is forced if −−line−offsets
is
used.
−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. If there
is more than one match in a line, each of them is shown
separately. If −o
is
combined with −v
(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 −−file−offsets
and
−−line−offsets
.
−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.
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.
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.
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.
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/fileIf 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.
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.
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.
Last updated: 17 December 2007 Copyright (c) 1997-2007 University of Cambridge.
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This manual page is taken from the PCRE library, which is distributed under the BSD license. |