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freeswitch/libs/pcre/doc/pcregrep.txt
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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.
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.
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 not recognized. An example is the pattern "(super)?(man)?",
in which all components are optional. This pattern finds all occur-
rences 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
-- 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 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 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 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.
-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 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 (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, 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.
-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 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.
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 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.
SEE ALSO
pcrepattern(3), pcretest(1).
AUTHOR
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
REVISION
Last updated: 01 March 2009
Copyright (c) 1997-2009 University of Cambridge.
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