Ubuntu Manpage: pcre2grep - a grep with Perl-compatible regular expressions.

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. Conversely, when one or both of these options
are used to specify patterns, 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 a
parameter that can be set by the --buffer-size option. The default value for this
parameter is specified when pcre2grep is built, with the default default being 20K. A
block of memory three times this size is used (to allow for buffering "before" and "after"
lines). An error occurs if a line overflows the buffer.

Patterns can be no longer than 8K 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 files whose
       names end in .gz or .bz2, respectively. You can find out whether your binary  has  support
       for  one  or  both  of  these  file  types  by  running  it with the --help option. If the
       appropriate support is not present, files are treated as plain text. The standard input is
       always so treated.

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 also identifies  binary
       files  in  this  manner.)  See  the  --binary-files option for a means of changing the way
       binary files are handled.

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 number lines of context after each matching line. 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. However, pcre2grep guarantees to have up to 8K
of following text available for context output.

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

-B number, --before-context=number
Output number lines of context before each matching line. 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. However, pcre2grep guarantees to have up to 8K
of preceding text available for context output.

--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 used for buffering files that
are being scanned.

-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 matches (or non-matches if -v is used) that would otherwise have
caused lines to be shown. By default, this count is the same as the number of
suppressed lines, but if the -M (multiline) option is used (without -v), there
may be more suppressed lines than the number of matches.

If no lines are selected, the number zero is output. If several files are are
being scanned, a count is output for each of them. However, if the --files-with-
matches option is also used, only those files whose counts are greater than zero
are listed. When -c is used, the -A, -B, and -C options are ignored.

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

--colour=value, --color=value
This option specifies under what circumstances the parts of a line that matched
a pattern should be coloured in the output. By default, the output is not
coloured. The value (which is optional, see above) may be "never", "always", or
"auto". In the latter case, colouring happens only if the standard output 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 the environment variable
PCRE2GREP_COLOUR or PCRE2GREP_COLOR. The value of this variable should be a
string of two numbers, separated by a semicolon. They are copied directly into
the control string for setting colour on a terminal, so it is your
responsibility to ensure that they make sense. If neither of the environment
variables is set, the default is "1;31", which gives red.

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

-d action, --directories=action
If an input path is a directory, "action" specifies how it is to be processed.
Valid values are "read" (the default 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.

-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used multiple 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
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 in order to specify multiple
patterns. If a file name matches both an --include and an --exclude pattern, 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 directory
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. What constitutes a newline when reading the file is the operating
system's default. 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. See also the comments
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. 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 terminal, 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 --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.

-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.

--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 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 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 directories 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 separate line.

-l, --files-with-matches
Instead of outputting lines from the files, just output the names of the files
containing lines that would have been output. 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
suppressing the listing of files with no matches.

--label=name
This option supplies a name to be used for the standard input when file names
are being output. If not supplied, "(standard input)" is used. There is no short
form for this option.

--line-buffered
When this option is given, 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). 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.

--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 separately. This option is mutually exclusive with --file-
offsets and --only-matching.

--locale=locale-name
This option specifies a locale to be used for pattern matching. It overrides the
value in the LC_ALL or LC_CTYPE environment 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 can require a very large amount of
memory, leading in some cases to a program crash if not enough is available.
Other patterns may take a very long time to search for all possible matching
strings. The pcre2_match() function that is called by pcre2grep to do the
matching has two parameters that can limit the resources that it uses.

The --match-limit option provides a means of limiting resource usage when
processing patterns that are not going to match, but which have a very large
number of possibilities in their search trees. The classic example is a pattern
that uses nested unlimited repeats. Internally, PCRE2 uses a function called
match() which it calls repeatedly (sometimes recursively). The limit set by
--match-limit is imposed on the number of times this function is called during a
match, which has the effect of limiting the amount of backtracking that can take
place.

The --recursion-limit option is similar to --match-limit, but instead of
limiting the total number of times that match() is called, it limits the depth
of recursive calls, which in turn limits the amount of memory that can be used.
The recursion depth is a smaller number than the total number of calls, because
not all calls to match() are recursive. This limit is of use only if it is set
smaller than --match-limit.

There are no short forms for these options. The default settings are specified
when the PCRE2 library is compiled, with the default default being 10 million.

-M, --multiline
Allow patterns to match more than one line. When this option is given, patterns
may usefully contain literal newline characters and internal occurrences of ^
and $ characters. The output for a successful match may consist of more than one
line. The first is the line in which the match started, and the last 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.

When this option is set, the PCRE2 library is called in "multiline" mode.
However, pcre2grep still processes the input line by line. The difference is
that a matched string may extend past the end of a line and continue on one or
more subsequent lines. The newline sequence 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. However, pcre2grep ensures
that at least 8K characters or the rest of the file (whichever is the shorter)
are available for forward matching, and similarly the previous 8K characters (or
all the previous characters, if fewer than 8K) are guaranteed to be available
for lookbehind assertions. 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
recognizes any of the preceding three types, and an "any" convention, in 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 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 modify 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, followed 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 problems. It
should never be needed in normal use.

-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. If -o is combined with -v (invert the sense of the match to find
non-matching lines), no output is generated, but the return code is set
appropriately. 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 --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 32 capturing parentheses are supported, and -o0 is
equivalent to -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 case. 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, in the
order the options are given. 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 option).

--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 settings. 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.

-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 subject 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 to match only whole words. This is equivalent to having \b at
the start and end of the pattern. 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 be anchored (each must start matching at the beginning of
a line) and in addition, require them to match entire lines. This is equivalent
to having ^ and $ characters at the start and end of each alternative top-level
branch in every pattern. 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 whatever newline sequences they have in the
       input. However, the setting of this option does not affect  the  interpretation  of  files
       specified  by  the -f, --exclude-from, or --include-from options, which are assumed to use
       the operating system's standard newline sequence, 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 appropriate 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). However, the --file-list, --file-offsets, --include-dir,
       --line-offsets, --locale, --match-limit, -M, --multiline, -N,  --newline,  --om-separator,
       --recursion-limit, -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 different  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 specified.  If a short
       form option is used, the data may follow immediately, or (with one exception) in the  next
       command line item. For example:

         -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.

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
       is a second option called --recursion-limit that sets a limit  on  the  amount  of  memory
       (usually stack) that is used (see the discussion of these options 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 inaccessible files does not affect the return code.

AUTHOR


       Philip Hazel
       University Computing Service
       Cambridge, England.

REVISION


       Last updated: 03 January 2015
       Copyright (c) 1997-2015 University of Cambridge.