xref: /aosp_15_r20/external/pcre/doc/pcre2grep.txt (revision 22dc650d8ae982c6770746019a6f94af92b0f024)

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

       By  default,  input  files are searched line by line, so pattern asser-
       tions about the beginning and end of a subject string (^,  $,  \A,  \Z,
       and  \z)  match  at  the  beginning  and  end of each line. When a line
       matches a pattern, it 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. For example, 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 -h and -H op-
       tions control whether or not file names are shown, and  the  -Z  option
       changes the file name terminator to a zero byte.

       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.

       When  matching with a multiline pattern, the size of the buffer must be
       at least half of the maximum match expected or the pattern  might  fail
       to match.

       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, --line-off-
       sets,  or  --output  is  used  to output only the part of the line that
       matched (either shown literally, or as an  offset),  the  behaviour  is
       different. In this situation, all the patterns are applied to the line.
       If  there  is  more  than one match, the one that begins nearest to the
       start of the subject is processed; if there is more than one  match  at
       that   position,  the  one  with  the  longest  matching  substring  is
       processed; if the matching substrings are equal, the first match  found
       is processed.

       Scanning with all the patterns resumes immediately following the match,
       so  that  later  matches  on the same line can be found. Note, however,
       that an overlapping match that starts in the middle  of  another  match
       will not be processed.

       The  above behaviour was changed at release 10.41 to be more compatible
       with GNU grep. In earlier releases, pcre2grep did not recognize matches
       from later patterns that were earlier in the subject.

       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

       Compile-time options for pcre2grep can set it up to use libz or  libbz2
       for  reading  compressed  files whose names end in .gz or .bz2, respec-
       tively. 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 appropriate support is not present, all  files  are  treated  as
       plain  text.  The standard input is always so treated. If a file with a
       .gz or .bz2 extension is not in fact compressed, it is read as a  plain
       text  file.  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  (the -Z option can be used to change the
                 file name terminator to a zero byte). 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 ex-
                 pected to be relatively small. When -c is  used,  -A  is  ig-
                 nored.

       -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 (the -Z option can  be
                 used  to  change  the file name terminator to a zero byte). 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 ignored.

       --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 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.
                 It is ignored if --file-offsets, --line-offsets, or  --output
                 is set. By default, output is not coloured. The value for the
                 --colour  option  (which  is  optional,  see  above)  may  be
                 "never", "always", or "auto". In the latter  case,  colouring
                 happens  only if the standard output is connected to a termi-
                 nal.  More resources are used when colouring is enabled,  be-
                 cause  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, --case-restrict
                 When case distinctions are being ignored in Unicode mode, two
                 ASCII letters (K and S) will by default match Unicode charac-
                 ters U+212A (Kelvin sign) and U+017F (long  S)  respectively,
                 as well as their lower case ASCII counterparts. When this op-
                 tion  is  set,  case equivalences are restricted such that no
                 ASCII character  matches  a  non-ASCII  character,  and  vice
                 versa.

       -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.

                 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.

       --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.  As  is  the  case
                 with  patterns  on  the command line, no delimiters should be
                 used. What constitutes a newline when reading the file is the
                 operating system's default interpretation of \n.  The  --new-
                 line  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.

                 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  matched
                 before the file's patterns. However, no 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, --colour  has  no
                 effect,  and 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 mutu-
                 ally exclusive with  --output,  --line-offsets,  and  --only-
                 matching.

       --group-separator=text
                 Output this text string instead of two hyphens between groups
                 of  lines  when -A, -B, or -C is in use. See also --no-group-
                 separator.

       -H, --with-filename
                 Force the inclusion of the file name at the start  of  output
                 lines when searching a single file. The file name is not nor-
                 mally  shown  in  this case.  By default, for matching lines,
                 the file name is followed by a colon; for  context  lines,  a
                 hyphen separator is used. The -Z option can be used to change
                 the terminator to a zero byte. 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 pre-
                 ceded by the file name. This option  overrides  any  previous
                 -h, -l, or -L options.

       -h, --no-filename
                 Suppress the output file names when searching multiple files.
                 File  names  are  normally  shown  when  multiple  files  are
                 searched. By default, for matching lines, the  file  name  is
                 followed by a colon; for context lines, a hyphen separator is
                 used. The -Z option can be used to change the terminator to a
                 zero  byte. 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 when pattern matching.
                 This applies when matching path names for inclusion or exclu-
                 sion as well as when matching lines in files.

       --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 by default, but if the -Z option is set,  they  are
                 separated  by  zero  bytes  instead  of newlines. 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, but
                 if the -Z option is set, they are separated by zero bytes in-
                 stead of newlines. 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 suppressing 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, --colour has  no  effect,
                 and  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 exclu-
                 sive 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,  and
                 a  match  is  allowed to continue past the end of the initial
                 line and onto one or more subsequent lines.

                 Patterns used with -M may usefully  contain  literal  newline
                 characters  and  internal  occurrences of ^ and $ characters,
                 because in multiline mode these can match  at  internal  new-
                 lines.  Because  pcre2grep is scanning multiple lines, the \Z
                 and \z assertions match only at the end of the last  line  in
                 the file.  The \A assertion matches at the start of the first
                 line  of a match. This can be any line in the file; it is not
                 anchored to the first line.

                 The output for a successful 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.

                 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 maximum amount of heap memory that
                 may be used for matching.

                 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-group-separator
                 Do not output a separator between groups of  lines  when  -A,
                 -B, or -C is in use. The default is to output a line contain-
                 ing two hyphens. See also --group-separator.

       --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 around 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,
                 --colour has no effect, and 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-offsets,  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.

       -P, --no-ucp
                 Starting  from release 10.43, when UTF/Unicode mode is speci-
                 fied with -u or -U, the PCRE2_UCP option is used by  default.
                 This means that the POSIX classes in patterns match more than
                 just  ASCII  characters.  For  example, [:digit:] matches any
                 Unicode  decimal  digit.  The  --no-ucp   option   suppresses
                 PCRE2_UCP,  thus restricting the POSIX classes to ASCII char-
                 acters, as was the case in earlier releases. Note that  there
                 are  now  more  fine-grained  option settings within patterns
                 that affect individual classes.  For  example,  when  in  UCP
                 mode, the sequence (?aP) restricts [:word:] to ASCII letters,
                 while allowing \w to match Unicode letters and digits.

       -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/Unicode mode. This option is available only if
                 PCRE2 has been compiled with UTF-8 support. All patterns (in-
                 cluding  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 er-
                 ror 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.

       -Z, --null
                 Terminate  files names in the regular output with a zero byte
                 (the NUL character) instead of what  would  normally  appear.
                 This  is  useful  when  file names contain unusual characters
                 such as colons, hyphens, or even newlines.  The  option  does
                 not apply to file names in error messages.


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 WITH GNU GREP

       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).
       However,  the  --case-restrict, --depth-limit, -E, --file-list, --file-
       offsets,   --heap-limit,   --include-dir,   --line-offsets,   --locale,
       --match-limit,  -M,  --multiline, -N, --newline, --no-ucp, --om-separa-
       tor, --output, -P, -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 in pcre2grep it is a regular expression to which
       the  -i  option  applies.  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: 22 December 2023
       Copyright (c) 1997-2023 University of Cambridge.


PCRE2 10.43                    22 December 2023                   PCRE2GREP(1)