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.
       The DJGPP port of pcregrep detects at runtime if LFN support is available
       or not. If only SFN support is available then apart of the .bz2 extension
       for bzip2 compressed files the .*bz extension also will be accepted as
       valid extension. The star stands for any valid character. If only SFN
       support is available then both .*gz and .**z extensions will be accepted
       together with the .gz extension as valid extension for files compressed
       with libz. Here also a star stands for any valid character.


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.
