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

       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.

       --        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 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-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. 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 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: 12 August 2009
       Copyright (c) 1997-2009 University of Cambridge.
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