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
       library  to  support  patterns  that  are  compatible  with the regular
       expressions 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
       indeed  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
       automatically 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
       (either shown literally, or as an offset), scanning resumes immediately
       following  the  match,  so that further matches on the same line can be
       found. If there are multiple  patterns,  they  are  all  tried  on  the
       remainder  of  the  line, but patterns that follow the one that matched
       are not tried on the earlier 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
       "(super)?(man)?", in which all components are  optional.  This  pattern
       finds  all  occurrences  of  both "super" and "man"; the output differs
       from matching with "super|man" when only the  matching  substrings  are
       being shown.

       If  the  LC_ALL or LC_CTYPE environment variable is set, 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.
       (GNU grep identifies binary files in this manner.) However, if the new-
       line 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
                 being 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 contigu-
                 ous  in the input file. The value of number is expected to be
                 relatively small. When -c is used, -A is ignored.

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

       -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
                 instead of a colon for the context lines. A  line  containing
                 "--"  is  output between each group of lines, unless they are
                 in fact contiguous in the input file. The value of number  is
                 expected  to  be  relatively  small.  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
                 binary 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
                 option,  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
                 option is also  used,  only  those  files  whose  counts  are
                 greater  than  zero  are listed. When -c is used, the -A, -B,
                 and -C options are ignored.

       --colour, --color
                 If this option is given without any data, it is equivalent to
                 "--colour=auto".   If  data  is required, it must be given in
                 the same shell item, separated by an equals sign.

       --colour=value, --color=value
                 This option specifies under what circumstances the parts of a
                 line that matched a pattern should be coloured in the output.
                 By default, the output is not coloured. The value  (which  is
                 optional,  see above) may be "never", "always", or "auto". In
                 the latter case, colouring happens only if the standard  out-
                 put  is connected to a terminal. More resources are used when
                 colouring is enabled, because 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
                 ignored, 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,
                 "action"  specifies  how  it is to be processed. Valid values
                 are "read" (the default) or "skip" (silently skip the path).

       -d action, --directories=action
                 If an input path is a directory, "action" specifies how it is
                 to  be  processed.   Valid  values are "read" (the default 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
                 directory 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
                 options 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
                 option.  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
                 excluded. 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
                 expression.  What  constitutes  a newline for this purpose is
                 controlled by the --newline option. The -w (match as a  word)
                 and  -x (match whole line) options can be used with -F.  They
                 apply to each of the fixed strings. A line is selected if any
                 of the fixed strings are found in it (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
                 options.

       -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
                 default. 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
                 options.

       -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 that 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
                 --exclude 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 that  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
                 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.
                 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. This opeion
                 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
                 library's default (usually the "C" locale) is used. There  is
                 no short form for this option.

       --match-limit=number
                 Processing  some  regular expression patterns 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
                 going to match, but which have a very large number of  possi-
                 bilities in their search trees. The classic example is a pat-
                 tern that uses nested unlimited  repeats.  Internally,  PCRE2
                 has  a  counter that is incremented each time around its main
                 processing  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.

       -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,
                 including newlines, and is followed  by  +  so  as  to  match
                 trailing  white  space  on the first line as well as possibly
                 handling 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.)

       -N newline-type, --newline=newline-type
                 The PCRE2 library supports  five  different  conventions  for
                 indicating  the  ends of lines. They are the single-character
                 sequences CR (carriage return) and LF  (linefeed),  the  two-
                 character  sequence CRLF, an "anycrlf" convention, which rec-
                 ognizes any of the preceding three types, and an  "any"  con-
                 vention, in which any Unicode line ending sequence is assumed
                 to end a line. The Unicode sequences are the three just  men-
                 tioned,  plus  VT  (vertical  tab,  U+000B),  FF  (form feed,
                 U+000C),  NEL  (next  line,  U+0085),  LS  (line   separator,
                 U+2028), and PS (paragraph separator, U+2029).

                 When  the  PCRE2  library  is  built,  a  default line-ending
                 sequence  is  specified.   This  is  normally  the   standard
                 sequence for the operating system. Unless otherwise specified
                 by this option, pcre2grep uses the  library's  default.   The
                 possible values for this option are CR, LF, CRLF, ANYCRLF, or
                 ANY. This 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
                 operating 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 whole line
                 that matched, output just the  given  text.  This  option  is
                 mutually  exclusive with --only-matching, --file-offsets, and
                 --line-offsets. Escape sequences starting with a dollar char-
                 acter  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> is replaced by the character  represented  by  the
                 given octal number; up to three digits are processed.

                 $x<digits>  is  replaced  by the character represented by the
                 given hexadecimal number; up to two digits are processed.

                 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
                 (invert 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
                 example, -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
                 "recurse".

       --recursion-limit=number
                 See --match-limit above.

       -s, --no-messages
                 Suppress error  messages  about  non-existent  or  unreadable
                 files.  Such  files  are quietly skipped. However, the return
                 code is still 2, even if matches were found in other files.

       -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
                 total 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-8
                 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  sub-
                 ject  lines  that  are scanned must be valid strings of UTF-8
                 characters.

       -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.

       -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
       order,  for  a  locale.  The first one that is set is used. This can be
       overridden by the --locale option. If  no  locale  is  set,  the  PCRE2
       library's default (usually the "C" locale) is used.


NEWLINES

       The -N (--newline) option allows pcre2grep to scan files with different
       newline conventions from the default. Any parts of the input files that
       are  written  to the standard output are copied identically, with what-
       ever newline sequences they have in the input. However, the setting  of
       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 --include-from options, nor does it affect the
       way in which pcre2grep writes informational messages  to  the  standard
       error and output streams. For these it uses the string "\n" to indicate
       newlines, relying on the C I/O library to convert this to an  appropri-
       ate sequence.


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, and --utf-8  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
       directory, you must separate the file name from the option, because the
       shell does not treat ~ specially unless it is at the start of an item.

       The exceptions to the above are the --colour (or --color)  and  --only-
       matching  options,  for  which  the  data  is optional. If one of these
       options does have data, it must be given in the first  form,  using  an
       equals character. Otherwise 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
       option. 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.

   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  other  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
       sequences  started  by  a dollar character: $<digits> or ${<digits>} is
       replaced by the captured substring of the given decimal  number,  which
       must  be greater than zero. If the number is greater than the number of
       capturing substrings, or if the capture is unset,  the  replacement  is
       empty.

       Any  other  character  is  substituted  by itself. In particular, $$ is
       replaced by a single dollar and $| is replaced  by  a  pipe  character.
       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)
       cause 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.

   Echoing a specific string

       This facility is always available, provided that callouts were not com-
       pletely disabled when pcre2grep was built. If the callout string starts
       with a pipe (vertical bar) character, the rest of the string is written
       to the output, having been passed through the same escape processing as
       text from the --output option. This provides a simple echoing  facility
       that  avoids  calling  an  external program or script. No terminator is
       added to the string, so if you want a  newline,  you  must  include  it
       explicitly.  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 relevant pattern with (*FAIL).


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
       resource  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).


AUTHOR

       Philip Hazel
       University Computing Service
       Cambridge, England.


REVISION

       Last updated: 24 November 2018
       Copyright (c) 1997-2018 University of Cambridge.
