PCRE2GREP(1) User Commands PCRE2GREP(1)

NAME

pcre2grep - a grep with Perl-compatible regular expressions.

SYNOPSIS

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

DESCRIPTION

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

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

pcre2grep Thursday /etc/motd

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

The first argument that follows any option settings is treated as the
single pattern to be matched when neither -e nor -f is present.
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.

PCRE2 10.45 04 February 2025 PCRE2GREP(1)