Provided by: pcre2-utils_10.42-1_amd64 
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
By default, input files are searched line by line. 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. For example, the -M option makes it possible to search for
strings that span line boundaries. What defines a line boundary is controlled by the -N
(--newline) option. The -h and -H options control whether or not file names are shown, and
the -Z option changes the file name terminator to a zero byte.
The amount of memory used for buffering files that are being scanned is controlled by
parameters that can be set by the --buffer-size and --max-buffer-size options. The first
of these sets the size of buffer that is obtained at the start of processing. If an input
file contains very long lines, a larger buffer may be needed; this is handled by
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, --line-offsets, or --output is used to output only the part of
the line that matched (either shown literally, or as an offset), the behaviour is
different. In this situation, all the patterns are applied to the line. If there is more
than one match, the one that begins nearest to the start of the subject is processed; if
there is more than one match at that position, the one with the longest matching substring
is processed; if the matching substrings are equal, the first match found is processed.
Scanning with all the patterns resumes immediately following the match, so that later
matches on the same line can be found. Note, however, that an overlapping match that
starts in the middle of another match will not be processed.
The above behaviour was changed at release 10.41 to be more compatible with GNU grep. In
earlier releases, pcre2grep did not recognize matches from later patterns that were
earlier in the subject.
Patterns that can match an empty string are accepted, but empty string matches are never
recognized. An example is the pattern "(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
Compile-time options for pcre2grep can set it up to use libz or libbz2 for reading
compressed files whose names end in .gz or .bz2, 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 appropriate support is not present, all files are treated as
plain text. The standard input is always so treated. If a file with a .gz or .bz2
extension is not in fact compressed, it is read as a plain text file. When input is from a
compressed .gz or .bz2 file, the --line-buffered option is ignored.
BINARY FILES
By default, a file that contains a binary zero byte within the first 1024 bytes is
identified as a binary file, and is processed specially. However, if the newline type is
specified as NUL, that is, the line terminator is a binary zero, the test for a binary
file is not applied. See the --binary-files option for a means of changing the way binary
files are handled.
BINARY ZEROS IN PATTERNS
Patterns passed from the command line are strings that are terminated by a binary zero, so
cannot contain internal zeros. However, patterns that are read from a file via the -f
option may contain binary zeros.
OPTIONS
The order in which some of the options appear can affect the output. For example, both the
-H and -l options affect the printing of file names. Whichever comes later in the command
line will be the one that takes effect. Similarly, except where noted below, if an option
is given twice, the later setting is used. Numerical values for options may be followed by
K or M, to signify multiplication by 1024 or 1024*1024 respectively.
-- This terminates the list of options. It is useful if the next item on the
command line starts with a hyphen but is not an option. This allows for the
processing of patterns and file names that start with hyphens.
-A number, --after-context=number
Output up to number lines of context after each matching line. Fewer lines are
output if the next match or the end of the file is reached, or if the processing
buffer size has been set too small. If file names and/or line numbers are being
output, a hyphen separator is used instead of a colon for the context lines (the
-Z option can be used to change the file name terminator to a zero byte). A line
containing "--" is output between each group of lines, unless they are in fact
contiguous in the input file. The value of number is 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.
--allow-lookaround-bsk
PCRE2 now forbids the use of \K in lookarounds by default, in line with Perl.
This option causes pcre2grep to set the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK option,
which enables this somewhat dangerous usage.
-B number, --before-context=number
Output up to number lines of context before each matching line. Fewer lines are
output if the previous match or the start of the file is within number lines, or
if the 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 (the -Z option can be used to change the file name terminator to a
zero byte). A line containing "--" is output between each group of lines, unless
they are in fact contiguous in the input file. The value of number is expected
to be relatively small. When -c is used, -B is ignored.
--binary-files=word
Specify how binary files are to be processed. If the word is "binary" (the
default), pattern matching is performed on 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 several 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. It is ignored if --file-offsets,
--line-offsets, or --output is set. By default, output is not coloured. The
value for the --colour option (which is optional, see above) may be "never",
"always", or "auto". In the latter case, colouring happens only if the standard
output is connected to a 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 contains any characters
other than semicolon or digits, the setting 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 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.
If -f is used with -e, the command line patterns are matched first, followed by
the patterns from the file(s), independent of the order in which these options
are specified.
--exclude=pattern
Files (but not directories) whose names match the pattern are skipped without
being processed. This applies to all files, whether listed on the command line,
obtained from --file-list, or by scanning a directory. The pattern is a PCRE2
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. As is the case with patterns on the
command line, no delimiters should be used. What constitutes a newline when
reading the file is the operating system's default interpretation of \n. The
--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.
If this option is given more than once, all the specified files are read. A data
line is output if any of the patterns match it. A file name can be given as "-"
to refer to the standard input. When -f is used, patterns specified on the
command line using -e may also be present; they are matched before the file's
patterns. However, no pattern is taken from the command line; all arguments are
treated as the names of paths to be searched.
--file-list=filename
Read a list of files and/or directories that are to be scanned from the given
file, one per line. What constitutes a newline when reading the file is the
operating system's 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 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, --colour has no effect, and no context is shown. That is, the -A, -B, and
-C options are ignored. If there is more than one match in a line, each of them
is shown separately. This option is mutually 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. The file name is not normally shown in this case. By default,
for matching lines, the file name is followed by a colon; for context lines, a
hyphen separator is used. The -Z option can be used to change the terminator to
a zero byte. If a line number is also being output, it follows the file name.
When the -M option causes a pattern to match more than one line, only the first
is 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. File names are
normally shown when multiple files are searched. By default, for matching lines,
the file name is followed by a colon; for context lines, a hyphen separator is
used. The -Z option can be used to change the terminator to a zero byte. If a
line number is also being output, it follows the file name. This option
overrides any previous -H, -L, or -l options.
--heap-limit=number
See --match-limit below.
--help Output a help message, giving brief details of the command options and file type
support, and then exit. Anything else on the command line is ignored.
-I Ignore binary files. This is equivalent to --binary-files=without-match.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
If any --include patterns are specified, the only files that are processed are
those whose names match one of the patterns and do not match an --exclude
pattern. This option does not affect directories, but it applies to all files,
whether listed on the command line, obtained from --file-list, or by scanning a
directory. The pattern is a PCRE2 regular 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 whose names match one of the patterns and do not match an
--exclude-dir pattern. This applies to all directories, whether listed on the
command line, obtained from --file-list, or by scanning a parent 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 by default, but if the -Z option is set, they
are separated by zero bytes instead of newlines. This option overrides any
previous -H, -h, or -l options.
-l, --files-with-matches
Instead of outputting lines from the files, just output the names of the files
containing lines that would have been output. Each file name is output once, on
a separate line, but if the -Z option is set, they are separated by zero bytes
instead of newlines. Searching normally stops as soon as a matching line is
found in a file. However, if the -c (count) option is also used, matching
continues in order to obtain the correct count, and those files that have at
least one match are listed along with their counts. Using this option with -c is
a way of suppressing the listing of files with no matches that occurs with -c on
its own. This option overrides any previous -H, -h, or -L options.
--label=name
This option supplies a name to be used for the standard input when file names
are being output. If not supplied, "(standard input)" is used. There is no short
form for this option.
--line-buffered
When this option is given, non-compressed input is read and processed line by
line, and the output is flushed after each write. By default, input is read in
large chunks, unless pcre2grep can determine that it is reading from a terminal,
which is currently possible only in Unix-like environments or Windows. Output to
terminal is normally automatically flushed by the operating system. This option
can be useful when the input or output is attached to a pipe and you do not want
pcre2grep to buffer up large amounts of data. However, its use will affect
performance, and the -M (multiline) option ceases to work. When input is from a
compressed .gz or .bz2 file, --line-buffered is ignored.
--line-offsets
Instead of showing lines or parts of lines that match, show each match as a line
number, the offset from the start of the line, and a length. The line number is
terminated by a colon (as usual; see the -n option), and the offset and length
are separated by a comma. In this mode, --colour has no effect, and no context
is shown. That is, the -A, -B, and -C options are ignored. If there is more than
one match in a line, each of them is shown separately. This option is mutually
exclusive with --output, --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.
-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 internal
occurrences of ^ and $ characters. The output for a successful match may consist
of more than one line. The first line is the line in which the match started,
and the last line is the line in which the match ended. If the matched string
ends with a newline sequence, the output ends at the end of that line. If -v is
set, none of the lines in a multi-line match are output. Once a match has been
handled, scanning restarts at the beginning of the line after the one in which
the match ended.
The newline sequence that separates multiple lines must be matched as part of
the pattern. For example, to find the phrase "regular expression" in a file
where "regular" might be at the end of a line and "expression" at the start of
the next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, 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.)
-m number, --max-count=number
Stop processing after finding number matching lines, or non-matching lines if -v
is also set. Any trailing context lines are output after the final match. In
multiline mode, each multiline match counts as just one line for this purpose.
If this limit is reached when reading the standard input from a regular file,
the file is left positioned just after the last matching line. If -c is also
set, the count that is output is never greater than number. This option has no
effect if used with -L, -l, or -q, or when just checking for a match in a binary
file.
--match-limit=number
Processing some regular expression patterns may take a very long time to search
for all possible matching strings. Others may require a very large amount of
memory. There are three options that set resource limits for matching.
The --match-limit option provides a means of limiting computing 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 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 maximum amount of heap memory that may be used for matching.
The --depth-limit option limits the depth of nested backtracking points, which
indirectly limits the amount of memory that is used. The amount of memory needed
for each backtracking 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 limits can be set when
the PCRE2 library is compiled; if they are not specified, the defaults are very
large and so effectively unlimited.
--max-buffer-size=number
This limits the expansion of the processing buffer, whose initial size can be
set by --buffer-size. The maximum buffer size is silently forced to be no
smaller than the starting buffer size.
-N newline-type, --newline=newline-type
Six different conventions for indicating the ends of lines in scanned files are
supported. For example:
pcre2grep -N CRLF 'some pattern' <file>
The newline type may be specified in upper, lower, or mixed case. If the newline
type is NUL, lines are separated by binary zero characters. The other types are
the single-character sequences CR (carriage return) and LF (linefeed), the two-
character sequence CRLF, an "anycrlf" type, which recognizes 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 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.
This option 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 text, --output=text
When there is a match, instead of outputting the line that matched, output just
the text specified in this option, followed by an operating-system standard
newline. In this mode, --colour has no effect, and no context is shown. That
is, the -A, -B, and -C options are ignored. The --newline option has no effect
on this option, which is mutually exclusive with --only-matching, --file-
offsets, and --line-offsets. However, like --only-matching, if there is more
than one match in a line, each of them causes a line of output.
Escape sequences starting with a dollar character may be used to insert the
contents of the matched part of the line and/or captured substrings into the
text.
$<digits> or ${<digits>} is replaced by the captured substring of the given
decimal number; zero substitutes the whole match. If the number is greater than
the number of capturing substrings, or if the capture is unset, the replacement
is empty.
$a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by
newline; $r by carriage return; $t by tab; $v by vertical tab.
$o<digits> or $o{<digits>} is replaced by the character whose code point is the
given octal number. In the first form, up to three octal digits are processed.
When more digits are needed in Unicode mode to specify a wide character, the
second form must be used.
$x<digits> or $x{<digits>} is replaced by the character represented by the given
hexadecimal number. In the first form, up to two hexadecimal digits are
processed. When more digits are needed in Unicode mode to specify a wide
character, the second form must be used.
Any other character is substituted by itself. In particular, $$ is replaced by a
single dollar.
-o, --only-matching
Show only the part of the line that matched a pattern instead of the whole line.
In this mode, no context is shown. That is, the -A, -B, and -C options are
ignored. If there is more than one match in a line, each of them is shown
separately, on a separate line of output. If -o is combined with -v (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 --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 parentheses 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 number 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 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
This is an obsolete synonym for --depth-limit. See --match-limit above for
details.
-s, --no-messages
Suppress error messages about non-existent or unreadable files. Such files are
quietly skipped. However, the return code is still 2, even if matches were found
in other files.
-t, --total-count
This option is useful when scanning more than one file. If used on its own, -t
suppresses all output except for a grand total number of matching lines (or non-
matching lines if -v is used) in all the files. If -t is used with -c, a grand
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 Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled
with UTF-8 support. All patterns (including those for any --exclude and
--include options) and all lines that are scanned must be valid strings of UTF-8
characters. If an invalid UTF-8 string is encountered, an error occurs.
-U, --utf-allow-invalid
As --utf, but in addition subject lines may contain invalid UTF-8 code unit
sequences. These can never form part of any pattern match. Patterns themselves,
however, must still be valid UTF-8 strings. This facility allows valid UTF-8
strings to be sought within arbitrary byte sequences in executable or other
binary files. For more details about matching in non-valid UTF-8 strings, see
the pcre2unicode(3) documentation.
-V, --version
Write the version numbers of pcre2grep and the PCRE2 library to the standard
output and then exit. Anything else on the command line is ignored.
-v, --invert-match
Invert the sense of the match, so that lines which do not match any of the
patterns are the ones that are found. When this option is set, options such as
--only-matching and --output, which specify parts of a match that are to be
output, are ignored.
-w, --word-regex, --word-regexp
Force the patterns only to match "words". That is, there must be a word boundary
at the start and end of each matched string. This is equivalent to having
"\b(?:" at the start of each pattern, and ")\b" at the end. This option applies
only to the patterns that are matched against the contents of files; it does not
apply to patterns specified by any of the --include or --exclude options.
-x, --line-regex, --line-regexp
Force the patterns to start matching only at the beginnings of lines, and in
addition, require them to match entire lines. In multiline mode the match may be
more than one line. This is equivalent to having "^(?:" at the start of each
pattern and ")$" at the end. This option applies only to the patterns that are
matched against the contents of files; it does not apply to patterns specified
by any of the --include or --exclude options.
-Z, --null
Terminate files names in the regular output with a zero byte (the NUL character)
instead of what would normally appear. This is useful when file names contain
unusual characters such as colons, hyphens, or even newlines. The option does
not apply to file names in error messages.
ENVIRONMENT VARIABLES
The environment variables LC_ALL and LC_CTYPE are examined, in that 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 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 --include-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 input. 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 newline 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). However, the --depth-limit, --file-list, --file-offsets,
--heap-limit, --include-dir, --line-offsets, --locale, --match-limit, -M, --multiline, -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 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.
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 patterns 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 argument is either a
number or a quoted string (see the pcre2callout documentation for details). Numbered
callouts are ignored by pcre2grep; only callouts with string arguments are useful.
Echoing a specific string
Starting the callout string with a pipe character invokes an echoing facility that avoids
calling an external program or script. This facility is always available, provided that
callouts were not completely disabled when pcre2grep was built. The rest of the callout
string is processed as a zero-terminated string, which means it should not contain any
internal binary zeros. It is written to the output, having first been passed through the
same escape processing as text from the --output (-O) option (see above). However, $0
cannot be used to insert a matched substring because the match is still in progress.
Instead, the single character '0' is inserted. Any syntax errors in the string (for
example, a dollar not followed by another character) causes the callout to be ignored. No
terminator is added to the output string, so if you want a newline, you must include it
explicitly using the escape $n. For example:
pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' <some file>
Matching continues normally after the string is output. If you want to see only the
callout output but not any output from an actual match, you should end the pattern with
(*FAIL).
Calling external programs or scripts
This facility can be independently disabled when pcre2grep is built. It is supported for
Windows, where a call to _spawnvp() is used, for VMS, where lib$spawn() is used, and for
any Unix-like environment where fork() and execv() are available.
If the callout string does not start with a pipe (vertical bar) character, it is parsed
into a list of substrings separated by pipe characters. The first substring must be an
executable name, with the following substrings specifying arguments:
executable_name|arg1|arg2|...
Any substring (including the executable name) may contain escape sequences started by a
dollar character. These are the same as for the --output (-O) option documented above,
except that $0 cannot insert the matched string because the match is still in progress.
Instead, the character '0' is inserted. If you need a literal dollar or pipe character in
any substring, use $$ or $| respectively. Here is an example:
echo -e "abcde\n12345" | pcre2grep \
'(?x)(.)(..(.))
(?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
Output:
Arg1: [a] [bcd] [d] Arg2: |a| ()
abcde
Arg1: [1] [234] [4] Arg2: |1| ()
12345
The parameters for the system call that is used to run the program or script are zero-
terminated strings. This means that binary zero characters in the callout argument will
cause premature termination of their substrings, and therefore should not be present. Any
syntax errors in the string (for example, a dollar not followed by another character)
causes the callout to be ignored. If running the program fails for any reason (including
the non-existence of the executable), a local matching failure occurs and the matcher
backtracks in the normal way.
MATCHING ERRORS
It is possible to supply a regular expression that takes a very long time to fail to match
certain lines. Such patterns normally involve nested indefinite repeats, for example:
(a+)*\d when matched against a line of a's with no final digit. The PCRE2 matching
function has a 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 inaccessible files does not affect the return code.
When run under VMS, the return code is placed in the symbol PCRE2GREP_RC because VMS does
not distinguish between exit(0) and exit(1).
SEE ALSO
pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3).
AUTHOR
Philip Hazel
Retired from University Computing Service
Cambridge, England.
REVISION
Last updated: 21 November 2022
Copyright (c) 1997-2022 University of Cambridge.