Provided by: pcregrep_8.31-2ubuntu2.3_amd64 
NAME
pcregrep - a grep with Perl-compatible regular expressions.
SYNOPSIS
pcregrep [options] [long options] [pattern] [path1 path2 ...] zpcregrep [options] [long
options] [pattern] [file1 file2 ...]
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 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.
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-matching, --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 follow 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.
zpcregrep is a wrapper script that allows pcregrep to work on gzip compressed files.
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.
BINARY FILES
By default, a file that contains a binary zero byte within the first 1024 bytes is
identified as a binary file, and is processed specially. (GNU grep also identifies binary
files in this manner.) See the --binary-files option for a means of changing the way
binary files are handled.
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 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.
-a, --text
Treat binary files as text. This is equivalent to --binary-files=text.
-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.
--binary-files=word
Specify how binary files are to be processed. If the word is "binary" (the
default), pattern matching is performed on binary files, but the only output is
"Binary file <name> matches" when a match succeeds. If the word is "text", which
is equivalent to the -a or --text option, binary files are processed in the same
way as any other file. In this case, when a match succeeds, the output may be
binary garbage, which can have nasty effects if sent to a terminal. If the word
is "without-match", which is equivalent to the -I option, binary files are not
processed at all; they are assumed not to be of interest.
--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 otherwise 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 output 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 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 regular files whose names match the pattern are
excluded. Subdirectories 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 subdirectories 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 (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 the names of paths to be searched.
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-list=filename
Read a list of files to be searched from the given file, one per line. Trailing
white space is removed from each line, and blank lines are ignored. These files
are searched before any others that may be listed on the command line. The
filename can be given as "-" to refer to the standard input. If --file and
--file-list are both specified as "-", patterns are read first. This is useful
only when the standard input is a terminal, from which further lines (the list
of files) can be read after an end-of-file indication.
--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 Treat binary files as never matching. This is equivalent to --binary-
files=without-match.
-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 regular files whose names match the
pattern are included. Subdirectories are always included and searched
recursively, subject to the --include-dir and --exclude-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.
--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
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.
-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 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
suppressing 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
currently possible only in Unix environments). Output to terminal is normally
automatically flushed by the operating system. 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 performance, 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 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.
--match-limit=number
Processing some regular expression patterns can require a very large amount of
memory, leading in some cases to a program 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 function 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 settings 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 characters 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 "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. 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
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 (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, followed 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 problems. 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 parentheses 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 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".
--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 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.
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. Any long option of the form --xxx-regexp (GNU terminology) is also available as
--xxx-regex (PCRE terminology). However, the --file-list, --file-offsets, --include-dir,
--line-offsets, --locale, --match-limit, -M, --multiline, -N, --newline, --recursion-
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 different 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 specified. If a short
form option is used, the data may follow immediately, or (with one exception) in the next
command line item. For example:
-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 inaccessible 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: 04 March 2012
Copyright (c) 1997-2012 University of Cambridge.