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 seman-
tics 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. 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 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.
The amount of memory used for buffering files that are being scanned is
controlled by a parameter that can be set by the --buffer-size option.
The default value for this parameter is specified when pcregrep is
built, with the default default being 20K. A block of memory three
times this size is used (to allow for buffering "before" and "after"
lines). An error occurs if a line overflows the buffer.
Patterns are limited to 8K or BUFSIZ bytes, 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.
By default, as soon as one pattern matches (or fails to match when -v
is used), no further patterns are considered. However, if --colour (or
--color) is used to colour the matching substrings, or if --only-match-
ing, --file-offsets, or --line-offsets is used to output only the part
of the line that matched (either shown literally, or as an offset),
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, but patterns that fol-
low the one that matched are not tried on the earlier part of the line.
This is the same behaviour as GNU grep, but it does mean that the order
in which multiple patterns are specified can affect the output when one
of the above options is used.
Patterns that can match an empty string are accepted, but empty string
matches are never recognized. An example is the pattern
"(super)?(man)?", in which all components are optional. This pattern
finds all occurrences of both "super" and "man"; the output differs
from matching with "super|man" when only the matching substrings are
being shown.
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.
SUPPORT FOR COMPRESSED FILES
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.
OPTIONS
The order in which some of the options appear can affect the output.
For example, both the -h and -l options affect the printing of file
names. Whichever comes later in the command line will be the one that
takes effect. Numerical values for options may be followed by K or M,
to signify multiplication by 1024 or 1024*1024 respectively.
-- This terminates 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.
--buffer-size=number
Set the parameter that controls how much memory is used for
buffering files that are being scanned.
-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 from the files that are being
scanned; instead output the number of lines that would other-
wise have been shown. If no lines are selected, the number
zero is output. If several files are are being scanned, a
count is output for each of them. However, if the --files-
with-matches option is also used, only those files whose
counts are greater than zero are listed. When -c is used, 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 parts of a
line that matched a pattern should be coloured in the output.
By default, the output is not coloured. The value (which is
optional, see above) may be "never", "always", or "auto". In
the latter case, colouring happens only if the standard out-
put is connected to a terminal. More resources are used when
colouring is enabled, because pcregrep has to search for all
possible matches in a line, not just one, in order to colour
them all.
The colour that is used can be specified by setting the envi-
ronment 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 mul-
tiple 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 multi-
ple use of -e is not the same as a single pattern with alter-
natives. For example, X|Y finds the first character in a line
that is X or Y, whereas if the two patterns are given sepa-
rately, 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 con-
sequence of the -r (recursive search) option, any regular
files whose names match the pattern are excluded. Subdirecto-
ries are not excluded by this option; they are searched
recursively, subject to the --exclude-dir and --include_dir
options. The pattern is a PCRE regular expression, and is
matched against the final component of the file name (not the
entire path). If a file name matches both --include and
--exclude, it is excluded. There is no short form for this
option.
--exclude-dir=pattern
When pcregrep is searching the contents of a directory as a
consequence of the -r (recursive search) option, any subdi-
rectories whose names match the pattern are excluded. (Note
that the --exclude option does not affect subdirectories.)
The pattern is a PCRE regular expression, and is matched
against the final component of the name (not the entire
path). If a subdirectory name matches both --include-dir and
--exclude-dir, 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. 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; for context lines, a hyphen separator
is used. If a line number is also being output, it follows
the file name.
-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; for context lines, a hyphen separator is used. If a
line number is also being output, it follows the file name.
--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 con-
sequence of the -r (recursive search) option, only those reg-
ular files whose names match the pattern are included. Subdi-
rectories are always included and searched recursively, sub-
ject to the --include-dir and --exclude-dir options. The pat-
tern is a PCRE regular expression, and is matched against the
final component of the file name (not the entire path). If a
file name matches both --include and --exclude, it is
excluded. There is no short form for this option.
--include-dir=pattern
When pcregrep is searching the contents of a directory as a
consequence of the -r (recursive search) option, only those
subdirectories whose names match the pattern are included.
(Note that the --include option does not affect subdirecto-
ries.) The pattern is a PCRE regular expression, and is
matched against the final component of the name (not the
entire path). If a subdirectory name matches both --include-
dir and --exclude-dir, 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 normally stops as soon as a matching line is found
in a file. However, if the -c (count) option is also used,
matching continues in order to obtain the correct count, and
those files that have at least one match are listed along
with their counts. Using this option with -c is a way of sup-
pressing the listing of files with no matches.
--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-buffered
When this option is given, input is read and processed line
by line, and the output is flushed after each write. By
default, input is read in large chunks, unless pcregrep can
determine that it is reading from a terminal (which is cur-
rently possible only in Unix environments). Output to termi-
nal is normally automatically flushed by the operating sys-
tem. This option can be useful when the input or output is
attached to a pipe and you do not want pcregrep to buffer up
large amounts of data. However, its use will affect perfor-
mance, and the -M (multiline) option ceases to work.
--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 sepa-
rately. This option is mutually exclusive with --file-offsets
and --only-matching.
--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.
--match-limit=number
Processing some regular expression patterns can require a
very large amount of memory, leading in some cases to a pro-
gram crash if not enough is available. Other patterns may
take a very long time to search for all possible matching
strings. The pcre_exec() function that is called by pcregrep
to do the matching has two parameters that can limit the
resources that it uses.
The --match-limit option provides a means of limiting
resource usage when processing patterns that are not going to
match, but which have a very large number of possibilities in
their search trees. The classic example is a pattern that
uses nested unlimited repeats. Internally, PCRE uses a func-
tion called match() which it calls repeatedly (sometimes
recursively). The limit set by --match-limit is imposed on
the number of times this function is called during a match,
which has the effect of limiting the amount of backtracking
that can take place.
The --recursion-limit option is similar to --match-limit, but
instead of limiting the total number of times that match() is
called, it limits the depth of recursive calls, which in turn
limits the amount of memory that can be used. The recursion
depth is a smaller number than the total number of calls,
because not all calls to match() are recursive. This limit is
of use only if it is set smaller than --match-limit.
There are no short forms for these options. The default set-
tings are specified when the PCRE library is compiled, with
the default default being 10 million.
-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 a successful match may consist of more than one
line, the last of which is the one in which the match ended.
If the matched string ends with a newline sequence the output
ends at the end of that 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. This option does not work when input
is read line by line (see --line-buffered.)
-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 men-
tioned, 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 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, fol-
lowed by a colon for matching lines or a hyphen for context
lines. If the filename is also being output, it precedes the
line number. This option is forced if --line-offsets is used.
--no-jit If the PCRE library is built with support for just-in-time
compiling (which speeds up matching), pcregrep automatically
makes use of this, unless it was explicitly disabled at build
time. This option can be used to disable the use of JIT at
run time. It is provided for testing and working round prob-
lems. It should never be needed in normal use.
-o, --only-matching
Show only the part of the line that matched a pattern instead
of the whole line. 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. If the matched portion of
the line is empty, nothing is output unless the file name or
line number are being printed, in which case they are shown
on an otherwise empty line. This option is mutually exclusive
with --file-offsets and --line-offsets.
-onumber, --only-matching=number
Show only the part of the line that matched the capturing
parentheses of the given number. Up to 32 capturing parenthe-
ses are supported. Because these options can be given without
an argument (see above), if an argument is present, it must
be given in the same shell item, for example, -o3 or --only-
matching=2. The comments given for the non-argument case
above also apply to this case. If the specified capturing
parentheses do not exist in the pattern, or were not set in
the match, nothing is output unless the file name or line
number are being printed.
-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".
--recursion-limit=number
See --match-limit above.
-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.
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
Many of the short and long forms of pcregrep's options are the same as
in the GNU grep program (version 2.5.4). Any long option of the form
--xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE
terminology). However, the --file-offsets, --include-dir, --line-off-
sets, --locale, --match-limit, -M, --multiline, -N, --newline, --recur-
sion-limit, -u, and --utf-8 options are specific to pcregrep, as is the
use of the --only-matching option with a capturing parentheses number.
Although most of the common options work the same way, a few are dif-
ferent in pcregrep. For example, the --include option's argument is a
glob for GNU grep, but a regular expression for pcregrep. If both the
-c and -l options are given, GNU grep lists only file names, without
counts, but pcregrep gives the counts.
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 (with one exception) in the next command line item. For exam-
ple:
-f/some/file
-f /some/file
The exception is the -o option, which may appear with or without data.
Because of this, if data is present, it must follow immediately in the
same item, for example -o3.
If a long form option is used, the data may appear in the same command
line item, separated by an equals character, or (with two exceptions)
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 exceptions to the above are the --colour (or --color) and --only-
matching options, for which the data is optional. If one of these
options does have data, it must be given in the first form, using an
equals character. Otherwise pcregrep will assume 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.
The --match-limit option of pcregrep can be used to set the overall
resource limit; there is a second option called --recursion-limit that
sets a limit on the amount of memory (usually stack) that is used (see
the discussion of these options above).
DIAGNOSTICS
Exit status is 0 if any matches were found, 1 if no matches were found,
and 2 for syntax errors, overlong lines, non-existent or inaccessible
files (even if matches were found in other files) or too many matching
errors. Using the -s option to suppress error messages about inaccessi-
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: 06 September 2011
Copyright (c) 1997-2011 University of Cambridge.
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