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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.

       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.

								   PCREGREP(1)
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