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PCRE2GREP(1) General Commands Manual PCRE2GREP(1)
NAME
pcre2grep - a grep with Perl-compatible regular expressions.
SYNOPSIS
pcre2grep [options] [long options] [pattern] [path1 path2 ...]
DESCRIPTION
pcre2grep searches files for character patterns, in the same way as
other grep commands do, but it uses the PCRE2 regular expression li-
brary to support patterns that are compatible with the regular expres-
sions of Perl 5. See pcre2syntax(3) for a quick-reference summary of
pattern syntax, or pcre2pattern(3) for a full description of the syntax
and semantics of the regular expressions that PCRE2 supports.
Patterns, whether supplied on the command line or in a separate file,
are given without delimiters. For example:
pcre2grep Thursday /etc/motd
If you attempt to use delimiters (for example, by surrounding a pattern
with slashes, as is common in Perl scripts), they are interpreted as
part of the pattern. Quotes can of course be used to delimit patterns
on the command line because they are interpreted by the shell, and in-
deed quotes are required if a pattern contains white space or shell
metacharacters.
The first argument that follows any option settings is treated as the
single pattern to be matched when neither -e nor -f is present. Con-
versely, when one or both of these options are used to specify pat-
terns, all arguments are treated as path names. At least one of -e, -f,
or an argument pattern must be provided.
If no files are specified, pcre2grep reads the standard input. The
standard input can also be referenced by a name consisting of a single
hyphen. For example:
pcre2grep some-pattern file1 - file3
By default, input files are searched line by line. Each line that
matches a pattern is copied to the standard output, and if there is
more than one file, the file name is output at the start of each line,
followed by a colon. However, there are options that can change how
pcre2grep behaves. For example, the -M option makes it possible to
search for strings that span line boundaries. What defines a line
boundary is controlled by the -N (--newline) option. The -h and -H op-
tions 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 au-
tomatically extending the buffer, up to the limit specified by --max-
buffer-size. The default values for these parameters can be set when
pcre2grep is built; if nothing is specified, the defaults are set to
20KiB and 1MiB respectively. An error occurs if a line is too long and
the buffer can no longer be expanded.
The block of memory that is actually used is three times the "buffer
size", to allow for buffering "before" and "after" lines. If the buffer
size is too small, fewer than requested "before" and "after" lines may
be output.
Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the
greater. BUFSIZ is defined in <stdio.h>. When there is more than one
pattern (specified by the use of -e and/or -f), each pattern is applied
to each line in the order in which they are defined, except that all
the -e patterns are tried before the -f patterns.
By default, as soon as one pattern matches a line, no further patterns
are considered. However, if --colour (or --color) is used to colour the
matching substrings, or if --only-matching, --file-offsets, or --line-
offsets is used to output only the part of the line that matched (ei-
ther shown literally, or as an offset), scanning resumes immediately
following the match, so that further matches on the same line can be
found. If there are multiple patterns, they are all tried on the re-
mainder of the line, but patterns that follow the one that matched are
not tried on the earlier matched part of the line.
This behaviour means that the order in which multiple patterns are
specified can affect the output when one of the above options is used.
This is no longer the same behaviour as GNU grep, which now manages to
display earlier matches for later patterns (as long as there is no
overlap).
Patterns that can match an empty string are accepted, but empty string
matches are never recognized. An example is the pattern "(su-
per)?(man)?", in which all components are optional. This pattern finds
all occurrences of both "super" and "man"; the output differs from
matching with "super|man" when only the matching substrings are being
shown.
If the LC_ALL or LC_CTYPE environment variable is set, pcre2grep uses
the value to set a locale when calling the PCRE2 library. The --locale
option can be used to override this.
SUPPORT FOR COMPRESSED FILES
It is possible to compile pcre2grep so that it uses libz or libbz2 to
read compressed files whose names end in .gz or .bz2, respectively. You
can find out whether your pcre2grep binary has support for one or both
of these file types by running it with the --help option. If the appro-
priate support is not present, all files are treated as plain text. The
standard input is always so treated. When input is from a compressed
.gz or .bz2 file, the --line-buffered option is ignored.
BINARY FILES
By default, a file that contains a binary zero byte within the first
1024 bytes is identified as a binary file, and is processed specially.
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 be-
ing 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 ex-
pected to be relatively small. When -c is used, -A is ig-
nored.
-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 process-
ing buffer size has been set too small. If file names and/or
line numbers are being output, a hyphen separator is used in-
stead of a colon for the context lines (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 bi-
nary files, but the only output is "Binary file <name>
matches" when a match succeeds. If the word is "text", which
is equivalent to the -a or --text option, binary files are
processed in the same way as any other file. In this case,
when a match succeeds, the output may be binary garbage,
which can have nasty effects if sent to a terminal. If the
word is "without-match", which is equivalent to the -I op-
tion, binary files are not processed at all; they are assumed
not to be of interest and are skipped without causing any
output or affecting the return code.
--buffer-size=number
Set the parameter that controls how much memory is obtained
at the start of processing for buffering files that are being
scanned. See also --max-buffer-size below.
-C number, --context=number
Output number lines of context both before and after each
matching line. This is equivalent to setting both -A and -B
to the same value.
-c, --count
Do not output lines from the files that are being scanned;
instead output the number of lines that would have been
shown, either because they matched, or, if -v is set, because
they failed to match. By default, this count is exactly the
same as the number of lines that would have been output, but
if the -M (multiline) option is used (without -v), there may
be more suppressed lines than the count (that is, the number
of matches).
If no lines are selected, the number zero is output. If sev-
eral files are are being scanned, a count is output for each
of them and the -t option can be used to cause a total to be
output at the end. However, if the --files-with-matches op-
tion is also used, only those files whose counts are greater
than zero are listed. When -c is used, the -A, -B, and -C op-
tions are ignored.
--colour, --color
If this option is given without any data, it is equivalent to
"--colour=auto". If data is required, it must be given in
the same shell item, separated by an equals sign.
--colour=value, --color=value
This option specifies under what circumstances the parts of a
line that matched a pattern should be coloured in the output.
By default, the output is not coloured. The value (which is
optional, see above) may be "never", "always", or "auto". In
the latter case, colouring happens only if the standard out-
put is connected to a terminal. More resources are used when
colouring is enabled, because pcre2grep has to search for all
possible matches in a line, not just one, in order to colour
them all.
The colour that is used can be specified by setting one of
the environment variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR,
PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that
order. If none of these are set, pcre2grep looks for
GREP_COLORS or GREP_COLOR (in that order). The value of the
variable should be a string of two numbers, separated by a
semicolon, except in the case of GREP_COLORS, which must
start with "ms=" or "mt=" followed by two semicolon-separated
colours, terminated by the end of the string or by a colon.
If GREP_COLORS does not start with "ms=" or "mt=" it is ig-
nored, and GREP_COLOR is checked.
If the string obtained from one of the above variables con-
tains any characters other than semicolon or digits, the set-
ting is ignored and the default colour is used. The string is
copied directly into the control string for setting colour on
a terminal, so it is your responsibility to ensure that the
values make sense. If no relevant environment variable is
set, the default is "1;31", which gives red.
-D action, --devices=action
If an input path is not a regular file or a directory, "ac-
tion" specifies how it is to be processed. Valid values are
"read" (the default) or "skip" (silently skip the path).
-d action, --directories=action
If an input path is a directory, "action" specifies how it is
to be processed. Valid values are "read" (the default in
non-Windows environments, for compatibility with GNU grep),
"recurse" (equivalent to the -r option), or "skip" (silently
skip the path, the default in Windows environments). In the
"read" case, directories are read as if they were ordinary
files. In some operating systems the effect of reading a di-
rectory like this is an immediate end-of-file; in others it
may provoke an error.
--depth-limit=number
See --match-limit below.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used mul-
tiple times in order to specify several patterns. It can also
be used as a way of specifying a single pattern that starts
with a hyphen. When -e is used, no argument pattern is taken
from the command line; all arguments are treated as file
names. There is no limit to the number of patterns. They are
applied to each line in the order in which they are defined
until one matches.
If -f is used with -e, the command line patterns are matched
first, followed by the patterns from the file(s), independent
of the order in which these options are specified. Note that
multiple use of -e is not the same as a single pattern with
alternatives. For example, X|Y finds the first character in a
line that is X or Y, whereas if the two patterns are given
separately, with X first, pcre2grep finds X if it is present,
even if it follows Y in the line. It finds Y only if there is
no X in the line. This matters only if you are using -o or
--colo(u)r to show the part(s) of the line that matched.
--exclude=pattern
Files (but not directories) whose names match the pattern are
skipped without being processed. This applies to all files,
whether listed on the command line, obtained from --file-
list, or by scanning a directory. The pattern is a PCRE2 reg-
ular expression, and is matched against the final component
of the file name, not the entire path. The -F, -w, and -x op-
tions do not apply to this pattern. The option may be given
any number of times in order to specify multiple patterns. If
a file name matches both an --include and an --exclude pat-
tern, it is excluded. There is no short form for this option.
--exclude-from=filename
Treat each non-empty line of the file as the data for an
--exclude option. What constitutes a newline when reading the
file is the operating system's default. The --newline option
has no effect on this option. This option may be given more
than once in order to specify a number of files to read.
--exclude-dir=pattern
Directories whose names match the pattern are skipped without
being processed, whatever the setting of the --recursive op-
tion. This applies to all directories, whether listed on the
command line, obtained from --file-list, or by scanning a
parent directory. The pattern is a PCRE2 regular expression,
and is matched against the final component of the directory
name, not the entire path. The -F, -w, and -x options do not
apply to this pattern. The option may be given any number of
times in order to specify more than one pattern. If a direc-
tory matches both --include-dir and --exclude-dir, it is ex-
cluded. There is no short form for this option.
-F, --fixed-strings
Interpret each data-matching pattern as a list of fixed
strings, separated by newlines, instead of as a regular ex-
pression. What constitutes a newline for this purpose is con-
trolled by the --newline option. The -w (match as a word) and
-x (match whole line) options can be used with -F. They ap-
ply to each of the fixed strings. A line is selected if any
of the fixed strings are found in it (subject to -w or -x, if
present). This option applies only to the patterns that are
matched against the contents of files; it does not apply to
patterns specified by any of the --include or --exclude op-
tions.
-f filename, --file=filename
Read patterns from the file, one per line, and match them
against each line of input. As is the case with patterns on
the command line, no delimiters should be used. What consti-
tutes a newline when reading the file is the operating sys-
tem's default interpretation of \n. The --newline option has
no effect on this option. Trailing white space is removed
from each line, and blank lines are ignored. An empty file
contains no patterns and therefore matches nothing. Patterns
read from a file in this way may contain binary zeros, which
are treated as ordinary data characters. See also the com-
ments about multiple patterns versus a single pattern with
alternatives in the description of -e above.
If this option is given more than once, all the specified
files are read. A data line is output if any of the patterns
match it. A file name can be given as "-" to refer to the
standard input. When -f is used, patterns specified on the
command line using -e may also be present; they are tested
before the file's patterns. However, no other pattern is
taken from the command line; all arguments are treated as the
names of paths to be searched.
--file-list=filename
Read a list of files and/or directories that are to be
scanned from the given file, one per line. What constitutes a
newline when reading the file is the operating system's de-
fault. Trailing white space is removed from each line, and
blank lines are ignored. These paths are processed before any
that are listed on the command line. The file name can be
given as "-" to refer to the standard input. If --file and
--file-list are both specified as "-", patterns are read
first. This is useful only when the standard input is a ter-
minal, from which further lines (the list of files) can be
read after an end-of-file indication. If this option is given
more than once, all the specified files are read.
--file-offsets
Instead of showing lines or parts of lines that match, show
each match as an offset from the start of the file and a
length, separated by a comma. In this mode, no context is
shown. That is, the -A, -B, and -C options are ignored. If
there is more than one match in a line, each of them is shown
separately. This option is mutually exclusive with --output,
--line-offsets, and --only-matching.
-H, --with-filename
Force the inclusion of the file name at the start of output
lines when searching a single file. The file name is not nor-
mally 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 pre-
ceded by the file name. This option overrides any previous
-h, -l, or -L options.
-h, --no-filename
Suppress the output file names when searching multiple files.
File names are normally shown when multiple files are
searched. By default, for matching lines, the file name is
followed by a colon; for context lines, a hyphen separator is
used. The -Z option can be used to change the terminator to a
zero byte. If a line number is also being output, it follows
the file name. This option overrides any previous -H, -L, or
-l options.
--heap-limit=number
See --match-limit below.
--help Output a help message, giving brief details of the command
options and file type support, and then exit. Anything else
on the command line is ignored.
-I Ignore binary files. This is equivalent to --binary-
files=without-match.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
If any --include patterns are specified, the only files that
are processed are those whose names match one of the patterns
and do not match an --exclude pattern. This option does not
affect directories, but it applies to all files, whether
listed on the command line, obtained from --file-list, or by
scanning a directory. The pattern is a PCRE2 regular expres-
sion, 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 --ex-
clude 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 direc-
tories 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 di-
rectory. The pattern is a PCRE2 regular expression, and is
matched against the final component of the directory name,
not the entire path. The -F, -w, and -x options do not apply
to this pattern. The option may be given any number of times.
If a directory matches both --include-dir and --exclude-dir,
it is excluded. There is no short form for this option.
-L, --files-without-match
Instead of outputting lines from the files, just output the
names of the files that do not contain any lines that would
have been output. Each file name is output once, on a sepa-
rate line 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 out-
put. Each file name is output once, on a separate line, but
if the -Z option is set, they are separated by zero bytes in-
stead 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, no context is shown.
That is, the -A, -B, and -C options are ignored. If there is
more than one match in a line, each of them is shown sepa-
rately. This option is mutually exclusive with --output,
--file-offsets, and --only-matching.
--locale=locale-name
This option specifies a locale to be used for pattern match-
ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
ronment variables. If no locale is specified, the PCRE2 li-
brary's default (usually the "C" locale) is used. There is no
short form for this option.
-M, --multiline
Allow patterns to match more than one line. When this option
is set, the PCRE2 library is called in "multiline" mode. This
allows a matched string to extend past the end of a line and
continue on one or more subsequent lines. Patterns used with
-M may usefully contain literal newline characters and inter-
nal occurrences of ^ and $ characters. The output for a suc-
cessful match may consist of more than one line. The first
line is the line in which the match started, and the last
line is the line in which the match ended. If the matched
string ends with a newline sequence, the output ends at the
end of that line. If -v is set, none of the lines in a
multi-line match are output. Once a match has been handled,
scanning restarts at the beginning of the line after the one
in which the match ended.
The newline sequence that separates multiple lines must be
matched as part of the pattern. For example, to find the
phrase "regular expression" in a file where "regular" might
be at the end of a line and "expression" at the start of the
next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, in-
cluding newlines, and is followed by + so as to match trail-
ing white space on the first line as well as possibly han-
dling a two-character newline sequence.
There is a limit to the number of lines that can be matched,
imposed by the way that pcre2grep buffers the input file as
it scans it. With a sufficiently large processing buffer,
this should not be a problem, but the -M option does not work
when input is read line by line (see --line-buffered.)
-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 comput-
ing resource usage when processing patterns that are not go-
ing to match, but which have a very large number of possibil-
ities in their search trees. The classic example is a pattern
that uses nested unlimited repeats. Internally, PCRE2 has a
counter that is incremented each time around its main pro-
cessing loop. If the value set by --match-limit is reached,
an error occurs.
The --heap-limit option specifies, as a number of kibibytes
(units of 1024 bytes), the maximum amount of heap memory that
may be used for matching.
The --depth-limit option limits the depth of nested back-
tracking points, which indirectly limits the amount of memory
that is used. The amount of memory needed for each backtrack-
ing point depends on the number of capturing parentheses in
the pattern, so the amount of memory that is used before this
limit acts varies from pattern to pattern. This limit is of
use only if it is set smaller than --match-limit.
There are no short forms for these options. The default lim-
its can be set when the PCRE2 library is compiled; if they
are not specified, the defaults are very large and so effec-
tively unlimited.
--max-buffer-size=number
This limits the expansion of the processing buffer, whose
initial size can be set by --buffer-size. The maximum buffer
size is silently forced to be no smaller than the starting
buffer size.
-N newline-type, --newline=newline-type
Six different conventions for indicating the ends of lines in
scanned files are supported. For example:
pcre2grep -N CRLF 'some pattern' <file>
The newline type may be specified in upper, lower, or mixed
case. If the newline type is NUL, lines are separated by bi-
nary zero characters. The other types are the single-charac-
ter sequences CR (carriage return) and LF (linefeed), the
two-character sequence CRLF, an "anycrlf" type, which recog-
nizes any of the preceding three types, and an "any" type,
for which any Unicode line ending sequence is assumed to end
a line. The Unicode sequences are the three just mentioned,
plus VT (vertical tab, U+000B), FF (form feed, U+000C), NEL
(next line, U+0085), LS (line separator, U+2028), and PS
(paragraph separator, U+2029).
When the PCRE2 library is built, a default line-ending se-
quence is specified. This is normally the standard sequence
for the operating system. Unless otherwise specified by this
option, pcre2grep uses the library's default.
This option makes it possible to use pcre2grep to scan files
that have come from other environments without having to mod-
ify their line endings. If the data that is being scanned
does not agree with the convention set by this option,
pcre2grep may behave in strange ways. Note that this option
does not apply to files specified by the -f, --exclude-from,
or --include-from options, which are expected to use the op-
erating system's standard newline sequence.
-n, --line-number
Precede each output line by its line number in the file, fol-
lowed by a colon for matching lines or a hyphen for context
lines. If the file name is also being output, it precedes the
line number. When the -M option causes a pattern to match
more than one line, only the first is preceded by its line
number. This option is forced if --line-offsets is used.
--no-jit If the PCRE2 library is built with support for just-in-time
compiling (which speeds up matching), pcre2grep automatically
makes use of this, unless it was explicitly disabled at build
time. This option can be used to disable the use of JIT at
run time. It is provided for testing and working round prob-
lems. It should never be needed in normal use.
-O text, --output=text
When there is a match, instead of outputting the line that
matched, output just the text specified in this option, fol-
lowed by an operating-system standard newline. In this mode,
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-off-
sets, 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 sub-
string of the given decimal number; zero substitutes the
whole match. If the number is greater than the number of cap-
turing substrings, or if the capture is unset, the replace-
ment is empty.
$a is replaced by bell; $b by backspace; $e by escape; $f by
form feed; $n by newline; $r by carriage return; $t by tab;
$v by vertical tab.
$o<digits> 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 sec-
ond form must be used.
$x<digits> or $x{<digits>} is replaced by the character rep-
resented 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 (in-
vert the sense of the match to find non-matching lines), no
output is generated, but the return code is set appropri-
ately. If the matched portion of the line is empty, nothing
is output unless the file name or line number are being
printed, in which case they are shown on an otherwise empty
line. This option is mutually exclusive with --output,
--file-offsets and --line-offsets.
-onumber, --only-matching=number
Show only the part of the line that matched the capturing
parentheses of the given number. Up to 50 capturing parenthe-
ses are supported by default. This limit can be changed via
the --om-capture option. A pattern may contain any number of
capturing parentheses, but only those whose number is within
the limit can be accessed by -o. An error occurs if the num-
ber specified by -o is greater than the limit.
-o0 is the same as -o without a number. Because these options
can be given without an argument (see above), if an argument
is present, it must be given in the same shell item, for ex-
ample, -o3 or --only-matching=2. The comments given for the
non-argument case above also apply to this option. If the
specified capturing parentheses do not exist in the pattern,
or were not set in the match, nothing is output unless the
file name or line number are being output.
If this option is given multiple times, multiple substrings
are output for each match, in the order the options are
given, and all on one line. For example, -o3 -o1 -o3 causes
the substrings matched by capturing parentheses 3 and 1 and
then 3 again to be output. By default, there is no separator
(but see the next but one option).
--om-capture=number
Set the number of capturing parentheses that can be accessed
by -o. The default is 50.
--om-separator=text
Specify a separating string for multiple occurrences of -o.
The default is an empty string. Separating strings are never
coloured.
-q, --quiet
Work quietly, that is, display nothing except error messages.
The exit status indicates whether or not any matches were
found.
-r, --recursive
If any given path is a directory, recursively scan the files
it contains, taking note of any --include and --exclude set-
tings. By default, a directory is read as a normal file; in
some operating systems this gives an immediate end-of-file.
This option is a shorthand for setting the -d option to "re-
curse".
--recursion-limit=number
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 to-
tal is output except when the previous output is just one
line. In other words, it is not output when just one file's
count is listed. If file names are being output, the grand
total is preceded by "TOTAL:". Otherwise, it appears as just
another number. The -t option is ignored when used with -L
(list files without matches), because the grand total would
always be zero.
-u, --utf Operate in UTF-8 mode. This option is available only if PCRE2
has been compiled with UTF-8 support. All patterns (including
those for any --exclude and --include options) and all 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 out-
put, 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 pat-
tern and ")$" at the end. This option applies only to the
patterns that are matched against the contents of files; it
does not apply to patterns specified by any of the --include
or --exclude options.
-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 or-
der, for a locale. The first one that is set is used. This can be over-
ridden by the --locale option. If no locale is set, the PCRE2 library's
default (usually the "C" locale) is used.
NEWLINES
The -N (--newline) option allows pcre2grep to scan files with newline
conventions that differ from the default. This option affects only the
way scanned files are processed. It does not affect the interpretation
of files specified by the -f, --file-list, --exclude-from, or --in-
clude-from options.
Any parts of the scanned input files that are written to the standard
output are copied with whatever newline sequences they have in the in-
put. However, if the final line of a file is output, and it does not
end with a newline sequence, a newline sequence is added. If the new-
line setting is CR, LF, CRLF or NUL, that line ending is output; for
the other settings (ANYCRLF or ANY) a single NL is used.
The newline setting does not affect the way in which pcre2grep writes
newlines in informational messages to the standard output and error
streams. Under Windows, the standard output is set to be binary, so
that "\r\n" at the ends of output lines that are copied from the input
is not converted to "\r\r\n" by the C I/O library. This means that any
messages written to the standard output must end with "\r\n". For all
other operating systems, and for all messages to the standard error
stream, "\n" is used.
OPTIONS COMPATIBILITY
Many of the short and long forms of pcre2grep's options are the same as
in the GNU grep program. Any long option of the form --xxx-regexp (GNU
terminology) is also available as --xxx-regex (PCRE2 terminology). How-
ever, the --depth-limit, --file-list, --file-offsets, --heap-limit,
--include-dir, --line-offsets, --locale, --match-limit, -M, --multi-
line, -N, --newline, --om-separator, --output, -u, --utf, -U, and
--utf-allow-invalid options are specific to pcre2grep, as is the use of
the --only-matching option with a capturing parentheses number.
Although most of the common options work the same way, a few are dif-
ferent in pcre2grep. For example, the --include option's argument is a
glob for GNU grep, but a regular expression for pcre2grep. If both the
-c and -l options are given, GNU grep lists only file names, without
counts, but pcre2grep gives the counts as well.
OPTIONS WITH DATA
There are four different ways in which an option with data can be spec-
ified. If a short form option is used, the data may follow immedi-
ately, or (with one exception) in the next command line item. For exam-
ple:
-f/some/file
-f /some/file
The exception is the -o option, which may appear with or without data.
Because of this, if data is present, it must follow immediately in the
same item, for example -o3.
If a long form option is used, the data may appear in the same command
line item, separated by an equals character, or (with two exceptions)
it may appear in the next command line item. For example:
--file=/some/file
--file /some/file
Note, however, that if you want to supply a file name beginning with ~
as data in a shell command, and have the shell expand ~ to a home di-
rectory, you must separate the file name from the option, because the
shell does not treat ~ specially unless it is at the start of an item.
The exceptions to the above are the --colour (or --color) and --only-
matching options, for which the data is optional. If one of these op-
tions does have data, it must be given in the first form, using an
equals character. Otherwise pcre2grep will assume that it has no data.
USING PCRE2'S CALLOUT FACILITY
pcre2grep has, by default, support for calling external programs or
scripts or echoing specific strings during matching by making use of
PCRE2's callout facility. However, this support can be completely or
partially disabled when pcre2grep is built. You can find out whether
your binary has support for callouts by running it with the --help op-
tion. If callout support is completely disabled, all callouts in pat-
terns are ignored by pcre2grep. If the facility is partially disabled,
calling external programs is not supported, and callouts that request
it are ignored.
A callout in a PCRE2 pattern is of the form (?C<arg>) where the argu-
ment is either a number or a quoted string (see the pcre2callout docu-
mentation for details). Numbered callouts are ignored by pcre2grep;
only callouts with string arguments are useful.
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 facil-
ity 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 con-
tain any internal binary zeros. It is written to the output, having
first been passed through the same escape processing as text from the
--output (-O) option (see above). However, $0 cannot be used to insert
a matched substring because the match is still in progress. Instead,
the single character '0' is inserted. Any syntax errors in the string
(for example, a dollar not followed by another character) causes the
callout to be ignored. No terminator is added to the output string, so
if you want a newline, you must include it explicitly using the escape
$n. For example:
pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' <some file>
Matching continues normally after the string is output. If you want to
see only the callout output but not any output from an actual match,
you should end the pattern with (*FAIL).
Calling external programs or scripts
This facility can be independently disabled when pcre2grep is built. It
is supported for Windows, where a call to _spawnvp() is used, for VMS,
where lib$spawn() is used, and for any Unix-like environment where
fork() and execv() are available.
If the callout string does not start with a pipe (vertical bar) charac-
ter, it is parsed into a list of substrings separated by pipe charac-
ters. The first substring must be an executable name, with the follow-
ing substrings specifying arguments:
executable_name|arg1|arg2|...
Any substring (including the executable name) may contain escape se-
quences started by a dollar character. These are the same as for the
--output (-O) option documented above, except that $0 cannot insert the
matched string because the match is still in progress. Instead, the
character '0' is inserted. If you need a literal dollar or pipe charac-
ter 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 charac-
ters in the callout argument will cause premature termination of their
substrings, and therefore should not be present. Any syntax errors in
the string (for example, a dollar not followed by another character)
causes the callout to be ignored. If running the program fails for any
reason (including the non-existence of the executable), a local match-
ing failure occurs and the matcher backtracks in the normal way.
MATCHING ERRORS
It is possible to supply a regular expression that takes a very long
time to fail to match certain lines. Such patterns normally involve
nested indefinite repeats, for example: (a+)*\d when matched against a
line of a's with no final digit. The PCRE2 matching function has a re-
source limit that causes it to abort in these circumstances. If this
happens, pcre2grep outputs an error message and the line that caused
the problem to the standard error stream. If there are more than 20
such errors, pcre2grep gives up.
The --match-limit option of pcre2grep can be used to set the overall
resource limit. There are also other limits that affect the amount of
memory used during matching; see the discussion of --heap-limit and
--depth-limit above.
DIAGNOSTICS
Exit status is 0 if any matches were found, 1 if no matches were found,
and 2 for syntax errors, overlong lines, non-existent or inaccessible
files (even if matches were found in other files) or too many matching
errors. Using the -s option to suppress error messages about inaccessi-
ble files does not affect the return code.
When run under VMS, the return code is placed in the symbol
PCRE2GREP_RC because VMS does not distinguish between exit(0) and
exit(1).
SEE ALSO
pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3).
AUTHOR
Philip Hazel
Retired from University Computing Service
Cambridge, England.
REVISION
Last updated: 30 July 2022
Copyright (c) 1997-2022 University of Cambridge.
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