path: root/doc/pcre2grep.txt

PCRE2GREP(1)                General Commands Manual               PCRE2GREP(1)



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

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


DESCRIPTION

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

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

         pcre2grep Thursday /etc/motd

       If you attempt to use delimiters (for example, by surrounding a pattern
       with slashes, as is common in Perl scripts), they  are  interpreted  as
       part  of  the pattern. Quotes can of course be used to delimit patterns
       on the command line because they are interpreted by the shell, and  in-
       deed  quotes  are  required  if a pattern contains white space or shell
       metacharacters.

       The first argument that follows any option settings is treated  as  the
       single  pattern  to be matched when neither -e nor -f is present.  Con-
       versely, when one or both of these options are  used  to  specify  pat-
       terns, all arguments are treated as path names. At least one of -e, -f,
       or an argument pattern must be provided.

       If no files are specified, pcre2grep  reads  the  standard  input.  The
       standard  input can also be referenced by a name consisting of a single
       hyphen.  For example:

         pcre2grep some-pattern file1 - file3

       Input files are searched line by  line.  By  default,  each  line  that
       matches  a  pattern  is  copied to the standard output, and if there is
       more than one file, the file name is output at the start of each  line,
       followed  by  a  colon.  However, there are options that can change how
       pcre2grep behaves. In particular, the -M option makes  it  possible  to
       search  for  strings  that  span  line  boundaries. What defines a line
       boundary is controlled by the -N (--newline) option.

       The amount of memory used for buffering files that are being scanned is
       controlled  by  parameters  that  can  be  set by the --buffer-size and
       --max-buffer-size options. The first of these sets the size  of  buffer
       that  is obtained at the start of processing. If an input file contains
       very long lines, a larger buffer may be needed; this is handled by  au-
       tomatically  extending  the buffer, up to the limit specified by --max-
       buffer-size. The default values for these parameters can  be  set  when
       pcre2grep  is  built;  if nothing is specified, the defaults are set to
       20KiB and 1MiB respectively. An error occurs if a line is too long  and
       the buffer can no longer be expanded.

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

       Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever  is  the
       greater.   BUFSIZ  is defined in <stdio.h>. When there is more than one
       pattern (specified by the use of -e and/or -f), each pattern is applied
       to  each  line  in the order in which they are defined, except that all
       the -e patterns are tried before the -f patterns.

       By default, as soon as one pattern matches a line, no further  patterns
       are considered. However, if --colour (or --color) is used to colour the
       matching substrings, or if --only-matching, --file-offsets, or  --line-
       offsets  is  used to output only the part of the line that matched (ei-
       ther shown literally, or as an offset),  scanning  resumes  immediately
       following  the  match,  so that further matches on the same line can be
       found. If there are multiple patterns, they are all tried  on  the  re-
       mainder  of the line, but patterns that follow the one that matched are
       not tried on the earlier part of the line.

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

       Patterns that can match an empty string are accepted, but empty  string
       matches   are  never  recognized.  An  example  is  the  pattern  "(su-
       per)?(man)?", in which all components are optional. This pattern  finds
       all  occurrences  of  both  "super"  and "man"; the output differs from
       matching with "super|man" when only the matching substrings  are  being
       shown.

       If  the  LC_ALL or LC_CTYPE environment variable is set, pcre2grep uses
       the value to set a locale when calling the PCRE2 library.  The --locale
       option can be used to override this.


SUPPORT FOR COMPRESSED FILES

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


BINARY FILES

       By  default,  a  file that contains a binary zero byte within the first
       1024 bytes is identified as a binary file, and is processed  specially.
       (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 be-
                 ing output, a hyphen separator is used instead of a colon for
                 the context lines. A line containing "--" is  output  between
                 each  group  of  lines, unless they are in fact contiguous in
                 the input file. The value of number is expected to  be  rela-
                 tively small. When -c is used, -A is ignored.

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

       -B number, --before-context=number
                 Output up to number lines of  context  before  each  matching
                 line.  Fewer  lines  are  output if the previous match or the
                 start of the file is within number lines, or if the  process-
                 ing  buffer size has been set too small. If file names and/or
                 line numbers are being output, a hyphen separator is used in-
                 stead  of  a  colon  for the context lines. A line containing
                 "--" is output between each group of lines, unless  they  are
                 in  fact contiguous in the input file. The value of number is
                 expected to be relatively small. When -c is used, -B  is  ig-
                 nored.

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

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

       -C number, --context=number
                 Output number lines of context both  before  and  after  each
                 matching  line.  This is equivalent to setting both -A and -B
                 to the same value.

       -c, --count
                 Do not output lines from the files that  are  being  scanned;
                 instead  output  the  number  of  lines  that would have been
                 shown, either because they matched, or, if -v is set, because
                 they  failed  to match. By default, this count is exactly the
                 same as the number of lines that would have been output,  but
                 if  the -M (multiline) option is used (without -v), there may
                 be more suppressed lines than the count (that is, the  number
                 of matches).

                 If  no lines are selected, the number zero is output. If sev-
                 eral files are are being scanned, a count is output for  each
                 of  them and the -t option can be used to cause a total to be
                 output at the end. However, if the  --files-with-matches  op-
                 tion  is also used, only those files whose counts are greater
                 than zero are listed. When -c is used, the -A, -B, and -C op-
                 tions are ignored.

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

       --colour=value, --color=value
                 This option specifies under what circumstances the parts of a
                 line that matched a pattern should be coloured in the output.
                 By  default,  the output is not coloured. The value (which is
                 optional, see above) may be "never", "always", or "auto".  In
                 the  latter case, colouring happens only if the standard out-
                 put is connected to a terminal. More resources are used  when
                 colouring is enabled, because pcre2grep has to search for all
                 possible matches in a line, not just one, in order to  colour
                 them all.

                 The  colour  that  is used can be specified by setting one of
                 the environment variables PCRE2GREP_COLOUR,  PCRE2GREP_COLOR,
                 PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that
                 order.  If  none  of  these  are  set,  pcre2grep  looks  for
                 GREP_COLORS  or  GREP_COLOR (in that order). The value of the
                 variable should be a string of two numbers,  separated  by  a
                 semicolon,  except  in  the  case  of GREP_COLORS, which must
                 start with "ms=" or "mt=" followed by two semicolon-separated
                 colours,  terminated  by the end of the string or by a colon.
                 If GREP_COLORS does not start with "ms=" or "mt=" it  is  ig-
                 nored, and GREP_COLOR is checked.

                 If  the  string obtained from one of the above variables con-
                 tains any characters other than semicolon or digits, the set-
                 ting is ignored and the default colour is used. The string is
                 copied directly into the control string for setting colour on
                 a  terminal,  so it is your responsibility to ensure that the
                 values make sense. If no  relevant  environment  variable  is
                 set, the default is "1;31", which gives red.

       -D action, --devices=action
                 If  an  input path is not a regular file or a directory, "ac-
                 tion" specifies how it is to be processed. Valid  values  are
                 "read" (the default) or "skip" (silently skip the path).

       -d action, --directories=action
                 If an input path is a directory, "action" specifies how it is
                 to be processed.  Valid values are  "read"  (the  default  in
                 non-Windows  environments,  for compatibility with GNU grep),
                 "recurse" (equivalent to the -r option), or "skip"  (silently
                 skip  the  path, the default in Windows environments). In the
                 "read" case, directories are read as if  they  were  ordinary
                 files.  In some operating systems the effect of reading a di-
                 rectory like this is an immediate end-of-file; in  others  it
                 may provoke an error.

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

       -e pattern, --regex=pattern, --regexp=pattern
                 Specify a pattern to be matched. This option can be used mul-
                 tiple times in order to specify several patterns. It can also
                 be  used  as a way of specifying a single pattern that starts
                 with a hyphen. When -e is used, no argument pattern is  taken
                 from  the  command  line;  all  arguments are treated as file
                 names. There is no limit to the number of patterns. They  are
                 applied  to  each line in the order in which they are defined
                 until one matches.

                 If -f is used with -e, the command line patterns are  matched
                 first, followed by the patterns from the file(s), independent
                 of the order in which these options are specified. Note  that
                 multiple  use  of -e is not the same as a single pattern with
                 alternatives. For example, X|Y finds the first character in a
                 line  that  is  X or Y, whereas if the two patterns are given
                 separately, with X first, pcre2grep finds X if it is present,
                 even if it follows Y in the line. It finds Y only if there is
                 no X in the line. This matters only if you are  using  -o  or
                 --colo(u)r to show the part(s) of the line that matched.

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

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

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

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

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

                 If  this  option  is  given more than once, all the specified
                 files are read. A data line is output if any of the  patterns
                 match  it.  A  file  name can be given as "-" to refer to the
                 standard input. When -f is used, patterns  specified  on  the
                 command  line  using  -e may also be present; they are tested
                 before the file's patterns.  However,  no  other  pattern  is
                 taken from the command line; all arguments are treated as the
                 names of paths to be searched.

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

       --file-offsets
                 Instead  of  showing lines or parts of lines that match, show
                 each match as an offset from the start  of  the  file  and  a
                 length,  separated  by  a  comma. In this mode, no context is
                 shown. That is, the -A, -B, and -C options  are  ignored.  If
                 there is more than one match in a line, each of them is shown
                 separately. This option is mutually exclusive with  --output,
                 --line-offsets, and --only-matching.

       -H, --with-filename
                 Force  the  inclusion of the file name at the start of output
                 lines when searching a single file. By default, the file name
                 is not shown in this case.  For matching lines, the file name
                 is followed by a colon; for context lines, a hyphen separator
                 is  used.  If  a line number is also being output, it follows
                 the file name. When the -M option causes a pattern  to  match
                 more  than  one  line, only the first is preceded by the file
                 name. This option overrides any previous -h, -l,  or  -L  op-
                 tions.

       -h, --no-filename
                 Suppress the output file names when searching multiple files.
                 By default, file names are  shown  when  multiple  files  are
                 searched.  For matching lines, the file name is followed by a
                 colon; for context lines, a hyphen separator is used.   If  a
                 line  number  is also being output, it follows the file name.
                 This option overrides any previous -H, -L, or -l options.

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

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

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

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

       --include=pattern
                 If  any --include patterns are specified, the only files that
                 are processed are those that match one of the  patterns  (and
                 do  not match an --exclude pattern). This option does not af-
                 fect directories, but it applies to all files, whether listed
                 on  the  command line, obtained from --file-list, or by scan-
                 ning a directory. The pattern is a PCRE2 regular  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.
                 If a file name matches both an  --include  and  an  --exclude
                 pattern, it is excluded.  There is no short form for this op-
                 tion.

       --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  di-
                 rectory.  The  pattern  is a PCRE2 regular expression, and is
                 matched against the final component of  the  directory  name,
                 not  the entire path. The -F, -w, and -x options do not apply
                 to this pattern. The option may be given any number of times.
                 If  a directory matches both --include-dir and --exclude-dir,
                 it is excluded. There is no short form for this option.

       -L, --files-without-match
                 Instead of outputting lines from the files, just  output  the
                 names  of  the files that do not contain any lines that would
                 have been output. Each file name is output once, on  a  sepa-
                 rate  line.  This option overrides any previous -H, -h, or -l
                 options.

       -l, --files-with-matches
                 Instead of outputting lines from the files, just  output  the
                 names of the files containing lines that would have been out-
                 put. Each file name is  output  once,  on  a  separate  line.
                 Searching  normally stops as soon as a matching line is found
                 in a file. However, if the -c (count) option  is  also  used,
                 matching  continues in order to obtain the correct count, and
                 those files that have at least one  match  are  listed  along
                 with their counts. Using this option with -c is a way of sup-
                 pressing the listing of files with no  matches.  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)  op-
                 tion  ceases  to work. When input is from a compressed .gz or
                 .bz2 file, --line-buffered is ignored.

       --line-offsets
                 Instead of showing lines or parts of lines that  match,  show
                 each match as a line number, the offset from the start of the
                 line, and a length. The line number is terminated by a  colon
                 (as  usual; see the -n option), and the offset and length are
                 separated by a comma. In this  mode,  no  context  is  shown.
                 That  is, the -A, -B, and -C options are ignored. If there is
                 more than one match in a line, each of them  is  shown  sepa-
                 rately.  This  option  is  mutually  exclusive with --output,
                 --file-offsets, and --only-matching.

       --locale=locale-name
                 This option specifies a locale to be used for pattern  match-
                 ing.  It  overrides the value in the LC_ALL or LC_CTYPE envi-
                 ronment variables. If no locale is specified, the  PCRE2  li-
                 brary's default (usually the "C" locale) is used. There is no
                 short form for this option.

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

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

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

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

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

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

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

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

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

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

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

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

                   pcre2grep -N CRLF 'some pattern' <file>

                 The newline type may be specified in upper, lower,  or  mixed
                 case.  If the newline type is NUL, lines are separated by bi-
                 nary zero characters. The other types are the  single-charac-
                 ter  sequences  CR  (carriage  return) and LF (linefeed), the
                 two-character sequence CRLF, an "anycrlf" type, which  recog-
                 nizes  any  of  the preceding three types, and an "any" type,
                 for which any Unicode line ending sequence is assumed to  end
                 a  line.  The Unicode sequences are the three just mentioned,
                 plus VT (vertical tab, U+000B), FF (form feed,  U+000C),  NEL
                 (next  line,  U+0085),  LS  (line  separator, U+2028), and PS
                 (paragraph separator, U+2029).

                 When the PCRE2 library is built, a  default  line-ending  se-
                 quence  is specified.  This is normally the standard sequence
                 for the operating system. Unless otherwise specified by  this
                 option, pcre2grep uses the library's default.

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

       -n, --line-number
                 Precede each output line by its line number in the file, fol-
                 lowed  by  a colon for matching lines or a hyphen for context
                 lines. If the file name is also being output, it precedes the
                 line  number.  When  the  -M option causes a pattern to match
                 more than one line, only the first is preceded  by  its  line
                 number. This option is forced if --line-offsets is used.

       --no-jit  If  the  PCRE2 library is built with support for just-in-time
                 compiling (which speeds up matching), pcre2grep automatically
                 makes use of this, unless it was explicitly disabled at build
                 time. This option can be used to disable the use  of  JIT  at
                 run  time. It is provided for testing and working round prob-
                 lems.  It should never be needed in normal use.

       -O text, --output=text
                 When there is a match, instead of outputting the  whole  line
                 that  matched, output just the given text, followed by an op-
                 erating-system standard newline.  The --newline option has no
                 effect  on  this  option,  which  is  mutually exclusive with
                 --only-matching, --file-offsets, and  --line-offsets.  Escape
                 sequences starting with a dollar character may be used to in-
                 sert the contents of the matched part of the line and/or cap-
                 tured 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  (in-
                 vert  the  sense of the match to find non-matching lines), no
                 output is generated, but the return  code  is  set  appropri-
                 ately.  If  the matched portion of the line is empty, nothing
                 is output unless the file  name  or  line  number  are  being
                 printed,  in  which case they are shown on an otherwise empty
                 line.  This  option  is  mutually  exclusive  with  --output,
                 --file-offsets and --line-offsets.

       -onumber, --only-matching=number
                 Show  only  the  part  of the line that matched the capturing
                 parentheses of the given number. Up to 50 capturing parenthe-
                 ses  are  supported by default. This limit can be changed via
                 the --om-capture option. A pattern may contain any number  of
                 capturing  parentheses, but only those whose number is within
                 the limit can be accessed by -o. An error occurs if the  num-
                 ber specified by -o is greater than the limit.

                 -o0 is the same as -o without a number. Because these options
                 can be given without an argument (see above), if an  argument
                 is  present, it must be given in the same shell item, for ex-
                 ample, -o3 or --only-matching=2. The comments given  for  the
                 non-argument  case  above  also  apply to this option. If the
                 specified capturing parentheses do not exist in the  pattern,
                 or  were  not  set in the match, nothing is output unless the
                 file name or line number are being output.

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

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

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

       -q, --quiet
                 Work quietly, that is, display nothing except error messages.
                 The  exit  status  indicates  whether or not any matches were
                 found.

       -r, --recursive
                 If any given path is a directory, recursively scan the  files
                 it  contains, taking note of any --include and --exclude set-
                 tings. By default, a directory is read as a normal  file;  in
                 some  operating  systems this gives an immediate end-of-file.
                 This option is a shorthand for setting the -d option to  "re-
                 curse".

       --recursion-limit=number
                 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 to-
                 tal  is  output  except  when the previous output is just one
                 line. In other words, it is not output when just  one  file's
                 count  is  listed.  If file names are being output, the grand
                 total is preceded by "TOTAL:". Otherwise, it appears as  just
                 another  number.  The  -t option is ignored when used with -L
                 (list files without matches), because the grand  total  would
                 always be zero.

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

       -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. This facility allows valid UTF-8 strings to be
                 sought in executable or other binary files.  For more details
                 about  matching in non-valid UTF-8 strings, see the pcre2uni-
                 code(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.

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

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


ENVIRONMENT VARIABLES

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


NEWLINES

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

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

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


OPTIONS COMPATIBILITY

       Many of the short and long forms of pcre2grep's options are the same as
       in the GNU grep program. Any long option of the form --xxx-regexp  (GNU
       terminology) is also available as --xxx-regex (PCRE2 terminology). How-
       ever, the  --depth-limit,  --file-list,  --file-offsets,  --heap-limit,
       --include-dir,  --line-offsets,  --locale,  --match-limit, -M, --multi-
       line, -N, --newline,  --om-separator,  --output,  -u,  --utf,  -U,  and
       --utf-allow-invalid options are specific to pcre2grep, as is the use of
       the --only-matching option with a capturing parentheses number.

       Although most of the common options work the same way, a few  are  dif-
       ferent  in pcre2grep. For example, the --include option's argument is a
       glob for GNU grep, but a regular expression for pcre2grep. If both  the
       -c  and  -l  options are given, GNU grep lists only file names, without
       counts, but pcre2grep gives the counts as well.


OPTIONS WITH DATA

       There are four different ways in which an option with data can be spec-
       ified.   If  a  short  form option is used, the data may follow immedi-
       ately, or (with one exception) in the next command line item. For exam-
       ple:

         -f/some/file
         -f /some/file

       The  exception is the -o option, which may appear with or without data.
       Because of this, if data is present, it must follow immediately in  the
       same item, for example -o3.

       If  a long form option is used, the data may appear in the same command
       line item, separated by an equals character, or (with  two  exceptions)
       it may appear in the next command line item. For example:

         --file=/some/file
         --file /some/file

       Note,  however, that if you want to supply a file name beginning with ~
       as data in a shell command, and have the shell expand ~ to a  home  di-
       rectory,  you  must separate the file name from the option, because the
       shell does not treat ~ specially unless it is at the start of an item.

       The exceptions to the above are the --colour (or --color)  and  --only-
       matching  options,  for which the data is optional. If one of these op-
       tions does have data, it must be given in  the  first  form,  using  an
       equals character. Otherwise pcre2grep will assume that it has no data.


USING PCRE2'S CALLOUT FACILITY

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

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

   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  se-
       quences  started by a dollar character: $<digits> or ${<digits>} is re-
       placed 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 re-
       placed 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  ex-
       plicitly.  Matching  continues  normally after the string is output. If
       you want to see only the callout output but not any output from an  ac-
       tual 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  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).


AUTHOR

       Philip Hazel
       University Computing Service
       Cambridge, England.


REVISION

       Last updated: 25 January 2020
       Copyright (c) 1997-2020 University of Cambridge.