doc/pcre2grep.txt

PCRE2GREP(1)                General Commands Manual               PCRE2GREP(1)



NAME
       pcre2grep - a grep with Perl-compatible regular expressions.

SYNOPSIS
       pcre2grep [options] [long options] [pattern] [path1 path2 ...]


DESCRIPTION

       pcre2grep  searches  files  for  character patterns, in the same way as
       other grep commands do, but it uses the PCRE2  regular  expression  li-
       brary  to support patterns that are compatible with the regular expres-
       sions of Perl 5. See pcre2syntax(3) for a  quick-reference  summary  of
       pattern syntax, or pcre2pattern(3) for a full description of the syntax
       and semantics of the regular expressions that PCRE2 supports.

       Patterns, whether supplied on the command line or in a  separate  file,
       are given without delimiters. For example:

         pcre2grep 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  in-
       deed  quotes  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, pcre2grep  reads  the  standard  input.  The
       standard  input can also be referenced by a name consisting of a single
       hyphen.  For example:

         pcre2grep some-pattern file1 - file3

       Input files are searched line by  line.  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
       pcre2grep behaves. In particular, the -M option makes  it  possible  to
       search  for  strings  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  parameters  that  can  be  set by the --buffer-size and
       --max-buffer-size options. The first of these sets the size  of  buffer
       that  is obtained at the start of processing. If an input file contains
       very long lines, a larger buffer may be needed; this is handled by  au-
       tomatically  extending  the buffer, up to the limit specified by --max-
       buffer-size. The default values for these parameters can  be  set  when
       pcre2grep  is  built;  if nothing is specified, the defaults are set to
       20KiB and 1MiB respectively. An error occurs if a line is too long  and
       the buffer can no longer be expanded.

       The  block  of  memory that is actually used is three times the "buffer
       size", to allow for buffering "before" and "after" lines. If the buffer
       size  is too small, fewer than requested "before" and "after" lines may
       be output.

       Patterns can be no longer than 8KiB 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 a line, no further  patterns
       are considered. However, if --colour (or --color) is used to colour the
       matching substrings, or if --only-matching, --file-offsets, or  --line-
       offsets  is  used to output only the part of the line that matched (ei-
       ther 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  re-
       mainder  of the line, but patterns that follow the one that matched are
       not tried on the earlier matched part of the line.

       This behaviour means that the order  in  which  multiple  patterns  are
       specified  can affect the output when one of the above options is used.
       This is no longer the same behaviour as GNU grep, which now manages  to
       display  earlier  matches  for  later  patterns (as long as there is no
       overlap).

       Patterns that can match an empty string are accepted, but empty  string
       matches   are  never  recognized.  An  example  is  the  pattern  "(su-
       per)?(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, pcre2grep uses
       the value to set a locale when calling the PCRE2 library.  The --locale
       option can be used to override this.


SUPPORT FOR COMPRESSED FILES

       It  is  possible to compile pcre2grep so that it uses libz or libbz2 to
       read compressed files whose names end in .gz or .bz2, respectively. You
       can  find out whether your pcre2grep binary has support for one or both
       of these file types by running it with the --help option. If the appro-
       priate support is not present, all files are treated as plain text. The
       standard input is always so treated. When input is  from  a  compressed
       .gz or .bz2 file, the --line-buffered option is ignored.


BINARY FILES

       By  default,  a  file that contains a binary zero byte within the first
       1024 bytes is identified as a binary file, and is processed  specially.
       However,  if  the  newline  type is specified as NUL, that is, the line
       terminator is a binary zero, the test for a binary file is not applied.
       See  the  --binary-files  option for a means of changing the way binary
       files are handled.


BINARY ZEROS IN PATTERNS

       Patterns passed from the command line are strings that  are  terminated
       by  a  binary zero, so cannot contain internal zeros. However, patterns
       that are read from a file via the -f option may contain binary zeros.


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.  Similarly,  except  where  noted below, if an option is
       given twice, the later setting is used. 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  up  to  number  lines  of context after each matching
                 line. Fewer lines are output if the next match or the end  of
                 the  file  is  reached,  or if the processing buffer size has
                 been set too small. If file names and/or line numbers are be-
                 ing output, a hyphen separator 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  rela-
                 tively small. When -c is used, -A is ignored.

       -a, --text
                 Treat  binary  files as text. This is equivalent to --binary-
                 files=text.

       --allow-lookaround-bsk
                 PCRE2 now forbids the use of \K in lookarounds by default, in
                 line  with  Perl.   This  option  causes pcre2grep to set the
                 PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK option, which  enables  this
                 somewhat dangerous usage.

       -B number, --before-context=number
                 Output  up  to  number  lines of context before each matching
                 line. Fewer lines are output if the  previous  match  or  the
                 start  of the file is within number lines, or if the process-
                 ing buffer size has been set too small. If file names  and/or
                 line numbers are being output, a hyphen separator is used in-
                 stead 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. When -c is used, -B is ig-
                 nored.

       --binary-files=word
                 Specify how binary files are to be processed. If the word  is
                 "binary"  (the default), pattern matching is performed on bi-
                 nary files, but  the  only  output  is  "Binary  file  <name>
                 matches"  when a match succeeds. If the word is "text", which
                 is equivalent to the -a or --text option,  binary  files  are
                 processed  in  the  same way as any other file. In this case,
                 when a match succeeds, the  output  may  be  binary  garbage,
                 which  can  have  nasty effects if sent to a terminal. If the
                 word is "without-match", which is equivalent to  the  -I  op-
                 tion, binary files are not processed at all; they are assumed
                 not to be of interest and are  skipped  without  causing  any
                 output or affecting the return code.

       --buffer-size=number
                 Set  the  parameter that controls how much memory is obtained
                 at the start of processing for buffering files that are being
                 scanned. See also --max-buffer-size below.

       -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  lines from the files that are being scanned;
                 instead output the number  of  lines  that  would  have  been
                 shown, either because they matched, or, if -v is set, because
                 they failed to match. By default, this count is  exactly  the
                 same  as the number of lines that would have been output, but
                 if the -M (multiline) option is used (without -v), there  may
                 be  more suppressed lines than the count (that is, the number
                 of matches).

                 If no lines are selected, the number zero is output. If  sev-
                 eral  files are are being scanned, a count is output for each
                 of them and the -t option can be used to cause a total to  be
                 output  at  the end. However, if the --files-with-matches op-
                 tion is also used, only those files whose counts are  greater
                 than zero are listed. When -c is used, the -A, -B, and -C op-
                 tions 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 pcre2grep 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  one  of
                 the  environment variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR,
                 PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that
                 order.  If  none  of  these  are  set,  pcre2grep  looks  for
                 GREP_COLORS or GREP_COLOR (in that order). The value  of  the
                 variable  should  be  a string of two numbers, separated by a
                 semicolon, except in the  case  of  GREP_COLORS,  which  must
                 start with "ms=" or "mt=" followed by two semicolon-separated
                 colours, terminated by the end of the string or by  a  colon.
                 If  GREP_COLORS  does not start with "ms=" or "mt=" it is ig-
                 nored, and GREP_COLOR is checked.

                 If the string obtained from one of the above  variables  con-
                 tains any characters other than semicolon or digits, the set-
                 ting is ignored and the default colour is used. The string is
                 copied directly into the control string for setting colour on
                 a terminal, so it is your responsibility to ensure  that  the
                 values  make  sense.  If  no relevant environment variable 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,  "ac-
                 tion"  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 in
                 non-Windows environments, for compatibility with  GNU  grep),
                 "recurse"  (equivalent to the -r option), or "skip" (silently
                 skip the path, the default in Windows environments).  In  the
                 "read"  case,  directories  are read as if they were ordinary
                 files. In some operating systems the effect of reading a  di-
                 rectory  like  this is an immediate end-of-file; in others it
                 may provoke an error.

       --depth-limit=number
                 See --match-limit below.

       -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 no limit to the number of patterns. They are
                 applied to each line in the order in which they  are  defined
                 until one matches.

                 If  -f is used with -e, the command line patterns are matched
                 first, followed by the patterns from the file(s), independent
                 of  the order in which these options are specified. Note that
                 multiple use of -e is not the same as a single  pattern  with
                 alternatives. For example, X|Y finds the first character in a
                 line that is X or Y, whereas if the two  patterns  are  given
                 separately, with X first, pcre2grep 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 matters only if you are using -o or
                 --colo(u)r to show the part(s) of the line that matched.

       --exclude=pattern
                 Files (but not directories) whose names match the pattern are
                 skipped  without  being processed. This applies to all files,
                 whether listed on the command  line,  obtained  from  --file-
                 list, or by scanning a directory. The pattern is a PCRE2 reg-
                 ular expression, and is matched against the  final  component
                 of the file name, not the entire path. The -F, -w, and -x op-
                 tions do not apply to this pattern. The option may  be  given
                 any number of times in order to specify multiple patterns. If
                 a file name matches both an --include and an  --exclude  pat-
                 tern, it is excluded. There is no short form for this option.

       --exclude-from=filename
                 Treat  each  non-empty  line  of  the file as the data for an
                 --exclude option. What constitutes a newline when reading the
                 file  is the operating system's default. The --newline option
                 has no effect on this option. This option may be  given  more
                 than once in order to specify a number of files to read.

       --exclude-dir=pattern
                 Directories whose names match the pattern are skipped without
                 being processed, whatever the setting of the --recursive  op-
                 tion.  This applies to all directories, whether listed on the
                 command line, obtained from --file-list,  or  by  scanning  a
                 parent  directory. The pattern is a PCRE2 regular expression,
                 and is matched against the final component of  the  directory
                 name,  not the entire path. The -F, -w, and -x options do not
                 apply to this pattern. The option may be given any number  of
                 times  in order to specify more than one pattern. If a direc-
                 tory matches both --include-dir and --exclude-dir, it is  ex-
                 cluded. There is no short form for this option.

       -F, --fixed-strings
                 Interpret  each  data-matching  pattern  as  a  list of fixed
                 strings, separated by newlines, instead of as a  regular  ex-
                 pression. What constitutes a newline for this purpose is con-
                 trolled by the --newline option. The -w (match as a word) and
                 -x  (match whole line) options can be used with -F.  They ap-
                 ply to each of the fixed strings. A line is selected  if  any
                 of the fixed strings are found in it (subject to -w or -x, if
                 present). This option applies only to the patterns  that  are
                 matched  against  the contents of files; it does not apply to
                 patterns specified by any of the --include or  --exclude  op-
                 tions.

       -f filename, --file=filename
                 Read  patterns  from  the  file, one per line, and match them
                 against each line of input. As is the case with  patterns  on
                 the  command line, no delimiters should be used. What consti-
                 tutes a newline when reading the file is the  operating  sys-
                 tem's  default interpretation of \n. The --newline option has
                 no effect on this option. Trailing  white  space  is  removed
                 from  each  line,  and blank lines are ignored. An empty file
                 contains no patterns and therefore matches nothing.  Patterns
                 read  from a file in this way may contain binary zeros, which
                 are treated as ordinary data characters. See  also  the  com-
                 ments  about  multiple  patterns versus a single pattern with
                 alternatives in the description of -e above.

                 If this option is given more than  once,  all  the  specified
                 files  are read. A data line is output if any of the patterns
                 match it. A file name 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 the
                 names of paths to be searched.

       --file-list=filename
                 Read  a  list  of  files  and/or  directories  that are to be
                 scanned from the given file, one per line. What constitutes a
                 newline  when  reading the file is the operating system's de-
                 fault. Trailing white space is removed from  each  line,  and
                 blank lines are ignored. These paths are processed before any
                 that are listed on the command line. The  file  name  can  be
                 given  as  "-"  to refer to the standard input. If --file and
                 --file-list are both specified  as  "-",  patterns  are  read
                 first.  This is useful only when the standard input is a ter-
                 minal, from which further lines (the list of  files)  can  be
                 read after an end-of-file indication. If this option is given
                 more than once, all the specified files are read.

       --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 --output,
                 --line-offsets, and --only-matching.

       -H, --with-filename
                 Force the inclusion of the file name at the start  of  output
                 lines when searching a single file. By default, the file name
                 is not shown in this case.  For matching lines, the file name
                 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. When the -M option causes a pattern to match
                 more than one line, only the first is preceded  by  the  file
                 name.  This  option  overrides any previous -h, -l, or -L op-
                 tions.

       -h, --no-filename
                 Suppress the output file names when searching multiple files.
                 By  default,  file  names  are  shown when multiple files are
                 searched. For matching lines, the file name 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.
                 This option overrides any previous -H, -L, or -l options.

       --heap-limit=number
                 See --match-limit below.

       --help    Output  a  help  message, giving brief details of the command
                 options and file type support, and then exit.  Anything  else
                 on the command line is ignored.

       -I        Ignore   binary   files.  This  is  equivalent  to  --binary-
                 files=without-match.

       -i, --ignore-case
                 Ignore upper/lower case distinctions during comparisons.

       --include=pattern
                 If any --include patterns are specified, the only files  that
                 are processed are those whose names match one of the patterns
                 and do not match an --exclude pattern. This option  does  not
                 affect  directories,  but  it  applies  to all files, whether
                 listed on the command line, obtained from --file-list, or  by
                 scanning  a directory. The pattern is a PCRE2 regular expres-
                 sion, and is matched against the final component of the  file
                 name,  not the entire path. The -F, -w, and -x options do not
                 apply to this pattern. The option may be given any number  of
                 times.  If a file name matches both an --include and an --ex-
                 clude pattern, it is excluded.  There is no  short  form  for
                 this option.

       --include-from=filename
                 Treat  each  non-empty  line  of  the file as the data for an
                 --include option. What constitutes a newline for this purpose
                 is  the  operating system's default. The --newline option has
                 no effect on this option. This option may be given any number
                 of times; all the files are read.

       --include-dir=pattern
                 If  any --include-dir patterns are specified, the only direc-
                 tories that are processed are those whose names match one  of
                 the  patterns and do not match an --exclude-dir pattern. This
                 applies to all directories, whether  listed  on  the  command
                 line,  obtained from --file-list, or by scanning a parent di-
                 rectory. The pattern is a PCRE2 regular  expression,  and  is
                 matched  against  the  final component of the directory name,
                 not the entire path. The -F, -w, and -x options do not  apply
                 to this pattern. The option may be given any number of times.
                 If a directory 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. This option overrides any previous -H, -h,  or  -l
                 options.

       -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 that occurs
                 with -c on its own. This option overrides  any  previous  -H,
                 -h, or -L options.

       --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, non-compressed 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
                 pcre2grep can determine that it is reading from  a  terminal,
                 which is currently possible only in Unix-like environments or
                 Windows. Output to terminal is normally automatically flushed
                 by  the  operating system. This option can be useful when the
                 input or output is attached to a pipe and  you  do  not  want
                 pcre2grep  to  buffer up large amounts of data.  However, its
                 use will affect performance, and the  -M  (multiline)  option
                 ceases  to  work. When input is from a compressed .gz or .bz2
                 file, --line-buffered is ignored.

       --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 --output,
                 --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  PCRE2  li-
                 brary'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 set, the PCRE2 library is called in "multiline" mode. This
                 allows a matched string to extend past the end of a line  and
                 continue  on one or more subsequent lines. Patterns used with
                 -M may usefully contain literal newline characters and inter-
                 nal  occurrences of ^ and $ characters. The output for a suc-
                 cessful match may consist of more than one  line.  The  first
                 line  is  the  line  in which the match started, and the last
                 line is the line in which the match  ended.  If  the  matched
                 string  ends  with a newline sequence, the output ends at the
                 end of that line.  If -v is set,  none  of  the  lines  in  a
                 multi-line  match  are output. Once a match has been handled,
                 scanning restarts at the beginning of the line after the  one
                 in which the match ended.

                 The  newline  sequence  that separates multiple lines must be
                 matched as part of the pattern.  For  example,  to  find  the
                 phrase  "regular  expression" in a file where "regular" might
                 be at the end of a line and "expression" at the start of  the
                 next line, you could use this command:

                   pcre2grep -M 'regular\s+expression' <file>

                 The \s escape sequence matches any white space character, in-
                 cluding newlines, and is followed by + so as to match  trail-
                 ing  white  space  on the first line as well as possibly han-
                 dling a two-character newline sequence.

                 There is a limit to the number of lines that can be  matched,
                 imposed  by  the way that pcre2grep buffers the input file as
                 it scans it. With a  sufficiently  large  processing  buffer,
                 this should not be a problem, but the -M option does not work
                 when input is read line by line (see --line-buffered.)

       -m number, --max-count=number
                 Stop processing after finding number matching lines, or  non-
                 matching  lines if -v is also set. Any trailing context lines
                 are output after the final match.  In  multiline  mode,  each
                 multiline  match counts as just one line for this purpose. If
                 this limit is reached when reading the standard input from  a
                 regular file, the file is left positioned just after the last
                 matching line.  If -c is also set, the count that  is  output
                 is  never  greater  than number. This option has no effect if
                 used with -L, -l, or -q, or when just checking for a match in
                 a binary file.

       --match-limit=number
                 Processing  some  regular expression patterns may take a very
                 long time to search for all possible matching strings. Others
                 may  require  a  very large amount of memory. There are three
                 options that set resource limits for matching.

                 The --match-limit option provides a means of limiting comput-
                 ing  resource usage when processing patterns that are not go-
                 ing to match, but which have a very large number of possibil-
                 ities in their search trees. The classic example is a pattern
                 that uses nested unlimited repeats. Internally, PCRE2  has  a
                 counter  that  is  incremented each time around its main pro-
                 cessing loop. If the value set by --match-limit  is  reached,
                 an error occurs.

                 The  --heap-limit  option specifies, as a number of kibibytes
                 (units of 1024 bytes), the amount of heap memory that may  be
                 used for matching. Heap memory is needed only if matching the
                 pattern requires a significant number of nested  backtracking
                 points to be remembered. This parameter can be set to zero to
                 forbid the use of heap memory altogether.

                 The --depth-limit option limits the  depth  of  nested  back-
                 tracking points, which indirectly limits the amount of memory
                 that is used. The amount of memory needed for each backtrack-
                 ing  point  depends on the number of capturing parentheses in
                 the pattern, so the amount of memory that is used before this
                 limit  acts  varies from pattern to pattern. This limit is of
                 use only if it is set smaller than --match-limit.

                 There are no short forms for these options. The default  lim-
                 its  can  be  set when the PCRE2 library is compiled; if they
                 are not specified, the defaults are very large and so  effec-
                 tively unlimited.

       --max-buffer-size=number
                 This  limits  the  expansion  of the processing buffer, whose
                 initial size can be set by --buffer-size. The maximum  buffer
                 size  is  silently  forced to be no smaller than the starting
                 buffer size.

       -N newline-type, --newline=newline-type
                 Six different conventions for indicating the ends of lines in
                 scanned files are supported. For example:

                   pcre2grep -N CRLF 'some pattern' <file>

                 The  newline  type may be specified in upper, lower, or mixed
                 case. If the newline type is NUL, lines are separated by  bi-
                 nary  zero characters. The other types are the single-charac-
                 ter sequences CR (carriage return)  and  LF  (linefeed),  the
                 two-character  sequence CRLF, an "anycrlf" type, which recog-
                 nizes any of the preceding three types, and  an  "any"  type,
                 for  which any Unicode line ending sequence is assumed to end
                 a line. The Unicode sequences are the three  just  mentioned,
                 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  PCRE2  library is built, a default line-ending se-
                 quence is specified.  This is normally the standard  sequence
                 for  the operating system. Unless otherwise specified by this
                 option, pcre2grep uses the library's default.

                 This option makes it possible to use pcre2grep to scan  files
                 that have come from other environments without having to mod-
                 ify their line endings. If the data  that  is  being  scanned
                 does  not  agree  with  the  convention  set  by this option,
                 pcre2grep may behave in strange ways. Note that  this  option
                 does  not apply to files specified by the -f, --exclude-from,
                 or --include-from options, which are expected to use the  op-
                 erating system's standard newline sequence.

       -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 file name is also being output, it precedes the
                 line number. When the -M option causes  a  pattern  to  match
                 more  than  one  line, only the first is preceded by its line
                 number. This option is forced if --line-offsets is used.

       --no-jit  If the PCRE2 library is built with support  for  just-in-time
                 compiling (which speeds up matching), pcre2grep 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 text, --output=text
                 When  there  is  a match, instead of outputting the line that
                 matched, output just the text specified in this option,  fol-
                 lowed  by an operating-system standard newline. In this mode,
                 no context is shown. That is, the -A, -B, and -C options  are
                 ignored.  The  --newline option has no effect on this option,
                 which is mutually exclusive with --only-matching, --file-off-
                 sets,  and  --line-offsets. However, like --only-matching, if
                 there is more than one match in a line, each of them causes a
                 line of output.

                 Escape sequences starting with a dollar character may be used
                 to insert the contents of the matched part of the line and/or
                 captured substrings into the text.

                 $<digits>  or  ${<digits>}  is  replaced by the captured sub-
                 string of the given  decimal  number;  zero  substitutes  the
                 whole match. If the number is greater than the number of cap-
                 turing substrings, or if the capture is unset,  the  replace-
                 ment is empty.

                 $a  is replaced by bell; $b by backspace; $e by escape; $f by
                 form feed; $n by newline; $r by carriage return; $t  by  tab;
                 $v by vertical tab.

                 $o<digits> or $o{<digits>} is replaced by the character whose
                 code point is the given octal number. In the first  form,  up
                 to  three  octal  digits are processed.  When more digits are
                 needed in Unicode mode to specify a wide character, the  sec-
                 ond form must be used.

                 $x<digits>  or $x{<digits>} is replaced by the character rep-
                 resented by the given hexadecimal number. In the first  form,
                 up  to two hexadecimal digits are processed. When more digits
                 are needed in Unicode mode to specify a wide  character,  the
                 second form must be used.

                 Any  other character is substituted by itself. In particular,
                 $$ is replaced by a single dollar.

       -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,
                 on a separate line of output. If -o is combined with -v  (in-
                 vert  the  sense of the match to find non-matching lines), no
                 output is generated, but the return  code  is  set  appropri-
                 ately.  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  --output,
                 --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 50 capturing parenthe-
                 ses  are  supported by default. This limit can be changed via
                 the --om-capture option. A pattern may contain any number  of
                 capturing  parentheses, but only those whose number is within
                 the limit can be accessed by -o. An error occurs if the  num-
                 ber specified by -o is greater than the limit.

                 -o0 is the same as -o without a number. 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 ex-
                 ample, -o3 or --only-matching=2. The comments given  for  the
                 non-argument  case  above  also  apply to this option. 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 output.

                 If this option is given multiple times,  multiple  substrings
                 are  output  for  each  match,  in  the order the options are
                 given, and all on one line. For example, -o3 -o1  -o3  causes
                 the  substrings  matched by capturing parentheses 3 and 1 and
                 then 3 again to be output. By default, there is no  separator
                 (but see the next but one option).

       --om-capture=number
                 Set  the number of capturing parentheses that can be accessed
                 by -o. The default is 50.

       --om-separator=text
                 Specify a separating string for multiple occurrences  of  -o.
                 The  default is an empty string. Separating strings are never
                 coloured.

       -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  "re-
                 curse".

       --recursion-limit=number
                 This  is  an obsolete synonym for --depth-limit. See --match-
                 limit above for details.

       -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.

       -t, --total-count
                 This option is useful when scanning more than  one  file.  If
                 used  on its own, -t suppresses all output except for a grand
                 total number of matching lines (or non-matching lines  if  -v
                 is used) in all the files. If -t is used with -c, a grand to-
                 tal is output except when the previous  output  is  just  one
                 line.  In  other words, it is not output when just one file's
                 count is listed. If file names are being  output,  the  grand
                 total  is preceded by "TOTAL:". Otherwise, it appears as just
                 another number. The -t option is ignored when  used  with  -L
                 (list  files  without matches), because the grand total would
                 always be zero.

       -u, --utf Operate in UTF-8 mode. This option is available only if PCRE2
                 has been compiled with UTF-8 support. All patterns (including
                 those for any --exclude and --include options) and all  lines
                 that  are  scanned must be valid strings of UTF-8 characters.
                 If an invalid UTF-8 string is encountered, an error occurs.

       -U, --utf-allow-invalid
                 As --utf, but in addition subject lines may  contain  invalid
                 UTF-8  code  unit sequences. These can never form part of any
                 pattern match. Patterns themselves, however,  must  still  be
                 valid UTF-8 strings. This facility allows valid UTF-8 strings
                 to be sought within arbitrary byte sequences in executable or
                 other  binary  files. For more details about matching in non-
                 valid UTF-8 strings, see the pcre2unicode(3) documentation.

       -V, --version
                 Write the version numbers of pcre2grep and the PCRE2  library
                 to  the  standard  output and then exit. Anything else on the
                 command line is ignored.

       -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. When
                 this option is  set,  options  such  as  --only-matching  and
                 --output,  which specify parts of a match that are to be out-
                 put, are ignored.

       -w, --word-regex, --word-regexp
                 Force the patterns only to match "words". That is, there must
                 be  a  word  boundary  at  the  start and end of each matched
                 string. This is equivalent to having "\b(?:" at the start  of
                 each  pattern, and ")\b" at the end. This option applies only
                 to the patterns that are  matched  against  the  contents  of
                 files;  it does not apply to patterns specified by any of the
                 --include or --exclude options.

       -x, --line-regex, --line-regexp
                 Force the patterns to start matching only at  the  beginnings
                 of  lines,  and  in  addition,  require  them to match entire
                 lines. In multiline mode the match may be more than one line.
                 This is equivalent to having "^(?:" at the start of each pat-
                 tern and ")$" at the end. This option  applies  only  to  the
                 patterns  that  are matched against the contents of files; it
                 does not apply to patterns specified by any of the  --include
                 or --exclude options.


ENVIRONMENT VARIABLES

       The environment variables LC_ALL and LC_CTYPE are examined, in that or-
       der, for a locale. The first one that is set is used. This can be over-
       ridden by the --locale option. If no locale is set, the PCRE2 library's
       default (usually the "C" locale) is used.


NEWLINES

       The -N (--newline) option allows pcre2grep to scan files  with  newline
       conventions  that differ from the default. This option affects only the
       way scanned files are processed. It does not affect the  interpretation
       of  files  specified  by  the -f, --file-list, --exclude-from, or --in-
       clude-from options.

       Any parts of the scanned input files that are written to  the  standard
       output  are copied with whatever newline sequences they have in the in-
       put. However, if the final line of a file is output, and  it  does  not
       end  with  a newline sequence, a newline sequence is added. If the new-
       line setting is CR, LF, CRLF or NUL, that line ending  is  output;  for
       the other settings (ANYCRLF or ANY) a single NL is used.

       The  newline  setting does not affect the way in which pcre2grep writes
       newlines in informational messages to the  standard  output  and  error
       streams.   Under  Windows,  the standard output is set to be binary, so
       that "\r\n" at the ends of output lines that are copied from the  input
       is  not converted to "\r\r\n" by the C I/O library. This means that any
       messages written to the standard output must end with "\r\n".  For  all
       other  operating  systems,  and  for all messages to the standard error
       stream, "\n" is used.


OPTIONS COMPATIBILITY

       Many of the short and long forms of pcre2grep'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 (PCRE2 terminology). How-
       ever,  the  --depth-limit,  --file-list,  --file-offsets, --heap-limit,
       --include-dir, --line-offsets, --locale,  --match-limit,  -M,  --multi-
       line,  -N,  --newline,  --om-separator,  --output,  -u,  --utf, -U, and
       --utf-allow-invalid options are specific to pcre2grep, 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 pcre2grep. For example, the --include option's argument is  a
       glob  for GNU grep, but a regular expression for pcre2grep. If both the
       -c and -l options are given, GNU grep lists only  file  names,  without
       counts, but pcre2grep gives the counts as well.


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 di-
       rectory, 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  op-
       tions  does  have  data,  it  must be given in the first form, using an
       equals character. Otherwise pcre2grep will assume that it has no data.


USING PCRE2'S CALLOUT FACILITY

       pcre2grep has, by default, support for  calling  external  programs  or
       scripts  or  echoing  specific strings during matching by making use of
       PCRE2's callout facility. However, this support can  be  completely  or
       partially  disabled  when  pcre2grep is built. You can find out whether
       your binary has support for callouts by running it with the --help  op-
       tion.  If  callout support is completely disabled, all callouts in pat-
       terns are ignored by pcre2grep.  If the facility is partially disabled,
       calling  external  programs is not supported, and callouts that request
       it are ignored.

       A callout in a PCRE2 pattern is of the form (?C<arg>) where  the  argu-
       ment  is either a number or a quoted string (see the pcre2callout docu-
       mentation for details). Numbered callouts  are  ignored  by  pcre2grep;
       only callouts with string arguments are useful.

   Echoing a specific string

       Starting  the  callout  string with a pipe character invokes an echoing
       facility that avoids calling an external program or script. This facil-
       ity  is  always  available,  provided that callouts were not completely
       disabled when pcre2grep was built. The rest of the  callout  string  is
       processed  as  a zero-terminated string, which means it should not con-
       tain any internal binary zeros. It is written  to  the  output,  having
       first  been  passed through the same escape processing as text from the
       --output (-O) option (see above). However, $0 cannot be used to  insert
       a  matched  substring  because the match is still in progress. Instead,
       the single character '0' is inserted. Any syntax errors in  the  string
       (for  example,  a  dollar not followed by another character) causes the
       callout to be ignored. No terminator is added to the output string,  so
       if  you want a newline, you must include it explicitly using the escape
       $n. For example:

         pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' <some file>

       Matching continues normally after the string is output. If you want  to
       see  only  the  callout output but not any output from an actual match,
       you should end the pattern with (*FAIL).

   Calling external programs or scripts

       This facility can be independently disabled when pcre2grep is built. It
       is  supported for Windows, where a call to _spawnvp() is used, for VMS,
       where lib$spawn() is used, and  for  any  Unix-like  environment  where
       fork() and execv() are available.

       If the callout string does not start with a pipe (vertical bar) charac-
       ter, it is parsed into a list of substrings separated by  pipe  charac-
       ters.  The first substring must be an executable name, with the follow-
       ing substrings specifying arguments:

         executable_name|arg1|arg2|...

       Any substring (including the executable name) may  contain  escape  se-
       quences  started  by  a dollar character. These are the same as for the
       --output (-O) option documented above, except that $0 cannot insert the
       matched  string  because  the  match is still in progress. Instead, the
       character '0' is inserted. If you need a literal dollar or pipe charac-
       ter in any substring, use $$ or $| respectively. Here is an example:

         echo -e "abcde\n12345" | pcre2grep \
           '(?x)(.)(..(.))
           (?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -

         Output:

           Arg1: [a] [bcd] [d] Arg2: |a| ()
           abcde
           Arg1: [1] [234] [4] Arg2: |1| ()
           12345

       The  parameters  for the system call that is used to run the program or
       script are zero-terminated strings. This means that binary zero charac-
       ters  in the callout argument will cause premature termination of their
       substrings, and therefore should not be present. Any syntax  errors  in
       the  string  (for  example, a dollar not followed by another character)
       causes the callout to be ignored.  If running the program fails for any
       reason  (including the non-existence of the executable), a local match-
       ing failure occurs and the matcher backtracks in the normal way.


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 PCRE2 matching function has a re-
       source limit that causes it to abort in these  circumstances.  If  this
       happens,  pcre2grep  outputs  an error message and the line that caused
       the problem to the standard error stream. If there  are  more  than  20
       such errors, pcre2grep gives up.

       The  --match-limit  option  of pcre2grep can be used to set the overall
       resource limit. There are also other limits that affect the  amount  of
       memory  used  during  matching;  see the discussion of --heap-limit and
       --depth-limit 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.

       When  run  under  VMS,  the  return  code  is  placed  in  the   symbol
       PCRE2GREP_RC  because  VMS  does  not  distinguish  between exit(0) and
       exit(1).


SEE ALSO

       pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3).


AUTHOR

       Philip Hazel
       Retired from University Computing Service
       Cambridge, England.


REVISION

       Last updated: 31 August 2021
       Copyright (c) 1997-2021 University of Cambridge.