Provided by: pcre2-utils_10.45-1_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, so pattern assertions about the beginning and end of a
subject string (^, $, \A, \Z, and \z) match at the beginning and end of each line. When a line matches a
pattern, it is copied to the standard output, and if there is more than one file, the file name is output
at the start of each line, followed by a colon. However, there are options that can change how pcre2grep
behaves. For example, the -M option makes it possible to search for strings that span line boundaries.
What defines a line boundary is controlled by the -N (--newline) option. The -h and -H 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.
When matching with a multiline pattern, the size of the buffer must be at least half of the maximum match
expected or the pattern might fail to match.
Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater. BUFSIZ is defined in
<stdio.h>. When there is more than one pattern (specified by the use of -e and/or -f), each pattern is
applied to each line in the order in which they are defined, except that all the -e patterns are tried
before the -f patterns.
By default, as soon as one pattern matches a line, no further patterns are considered. However, if
--colour (or --color) is used to colour the matching substrings, or if --only-matching, --file-offsets,
--line-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 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, --case-restrict
When case distinctions are being ignored in Unicode mode, two ASCII letters (K and S) will by
default match Unicode characters U+212A (Kelvin sign) and U+017F (long S) respectively, as well
as their lower case ASCII counterparts. When this option is set, case equivalences are
restricted such that no ASCII character matches a non-ASCII character, and vice versa.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used 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 unless the --posix-
pattern-file option is also provided. 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 character literals.
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.
--group-separator=text
Output this text string instead of two hyphens between groups of lines when -A, -B, or -C is in
use. See also --no-group-separator.
-H, --with-filename
Force the inclusion of the file name at the start of output lines when searching a single file.
The file name is not 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 when pattern matching. This applies when matching path
names for inclusion or exclusion as well as when matching lines in files.
--include=pattern
If any --include patterns are specified, the only files that are processed are those whose
names match one of the patterns and do not match an --exclude pattern. This option does not
affect directories, but it applies to all files, whether listed on the command line, obtained
from --file-list, or by scanning a directory. The pattern is a PCRE2 regular 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, and a match is allowed to continue past the end of the initial line
and onto one or more subsequent lines.
Patterns used with -M may usefully contain literal newline characters and internal occurrences
of ^ and $ characters, because in multiline mode these can match at internal newlines. Because
pcre2grep is scanning multiple lines, the \Z and \z assertions match only at the end of the
last line in the file. The \A assertion matches at the start of the first line of a match.
This can be any line in the file; it is not anchored to the first line.
The output for a successful match may consist of more than one line. The first line is the line
in which the match started, and the last line is the line in which the match ended. If the
matched string ends with a newline sequence, the output ends at the end of that line. If -v is
set, none of the lines in a multi-line match are output. Once a match has been handled,
scanning restarts at the beginning of the line after the one in which the match ended.
The newline sequence that separates multiple lines must be matched as part of the pattern. For
example, to find the phrase "regular expression" in a file where "regular" might be at the end
of a line and "expression" at the start of the next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, 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.
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-group-separator
Do not output a separator between groups of lines when -A, -B, or -C is in use. The default is
to output a line containing two hyphens. See also --group-separator.
--no-jit If the PCRE2 library is built with support for just-in-time compiling (which speeds up
matching), pcre2grep automatically makes use of this, unless it was explicitly disabled at
build time. This option can be used to disable the use of JIT at run time. It is provided for
testing and working around 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; $&
(or the legacy $0) 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.
-P, --no-ucp
Starting from release 10.43, when UTF/Unicode mode is specified with -u or -U, the PCRE2_UCP
option is used by default. This means that the POSIX classes in patterns match more than just
ASCII characters. For example, [:digit:] matches any Unicode decimal digit. The --no-ucp option
suppresses PCRE2_UCP, thus restricting the POSIX classes to ASCII characters, as was the case
in earlier releases. Note that there are now more fine-grained option settings within patterns
that affect individual classes. For example, when in UCP mode, the sequence (?aP) restricts
[:word:] to ASCII letters, while allowing \w to match Unicode letters and digits.
--posix-pattern-file
When patterns are provided with the -f option, do not trim trailing spaces or ignore empty
lines in a similar way than other grep tools. To keep the behaviour consistent with older
versions, if the pattern read was terminated with CRLF (as character literals) then both
characters won't be included as part of it, so if you really need to have pattern ending in
'\r', use a escape sequence or provide it by a different method.
-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/Unicode 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 WITH GNU GREP
Many of the short and long forms of pcre2grep's options are the same as in the GNU grep program. Any long
option of the form --xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE2 terminology).
However, the --case-restrict, --depth-limit, -E, --file-list, --file-offsets, --heap-limit, --include-
dir, --line-offsets, --locale, --match-limit, -M, --multiline, -N, --newline, --no-ucp, --om-separator,
--output, -P, -u, --utf, -U, and --utf-allow-invalid options are specific to pcre2grep, as is the use of
the --only-matching option with a capturing parentheses number.
Although most of the common options work the same way, a few are different in pcre2grep. For example, the
--include option's argument is a glob for GNU grep, but in pcre2grep it is a regular expression to which
the -i option applies. If both the -c and -l options are given, GNU grep lists only file names, without
counts, but pcre2grep gives the counts as well.
OPTIONS WITH DATA
There are four different ways in which an option with data can be 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, callouts in patterns are
forbidden 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 or $& 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 or $& 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: 04 February 2025
Copyright (c) 1997-2023 University of Cambridge.