trunk/doc/pcregrep.txt

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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