pcre2 (10.42)
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NAME
pcre2grep - a grep with Perl-compatible regular expressions.
SYNOPSIS
pcre2grep [options] [long options] [pattern] [path1 path2 ...]
DESCRIPTION
pcre2grep searches files for character patterns, in the same way as other grep commands do, but it uses the PCRE2
regular expression library to support patterns that are compatible with the regular expressions of Perl 5. See
pcre2syntax(3) for a quick-reference summary of pattern syntax, or pcre2pattern(3) for a full description of the
syntax and semantics of the regular expressions that PCRE2 supports.
Patterns, whether supplied on the command line or in a separate file, are given without delimiters. For example:
pcre2grep Thursday /etc/motd
If you attempt to use delimiters (for example, by surrounding a pattern with slashes, as is common in Perl
scripts), they are interpreted as part of the pattern. Quotes can of course be used to delimit patterns on the
command line because they are interpreted by the shell, and indeed quotes are required if a pattern contains
white space or shell metacharacters.
The first argument that follows any option settings is treated as the single pattern to be matched when neither
-e nor -f is present. Conversely, when one or both of these options are used to specify patterns, all arguments
are treated as path names. At least one of -e, -f, or an argument pattern must be provided.
If no files are specified, pcre2grep reads the standard input. The standard input can also be referenced by a
name consisting of a single hyphen. For example:
pcre2grep some-pattern file1 - file3
By default, input files are searched line by line. Each line that matches a pattern is copied to the standard
output, and if there is more than one file, the file name is output at the start of each line, followed by a
colon. However, there are options that can change how pcre2grep behaves. For example, the -M option makes it
possible to search for strings that span line boundaries. What defines a line boundary is controlled by the -N
(--newline) option. The -h and -H options control whether or not file names are shown, and the -Z option changes
the file name terminator to a zero byte.
The amount of memory used for buffering files that are being scanned is controlled by parameters that can be set
by the --buffer-size and --max-buffer-size options. The first of these sets the size of buffer that is obtained
at the start of processing. If an input file contains very long lines, a larger buffer may be needed; this is
handled by automatically extending the buffer, up to the limit specified by --max-buffer-size. The default values
for these parameters can be set when pcre2grep is built; if nothing is specified, the defaults are set to 20KiB
and 1MiB respectively. An error occurs if a line is too long and the buffer can no longer be expanded.
The block of memory that is actually used is three times the "buffer size", to allow for buffering "before" and
"after" lines. If the buffer size is too small, fewer than requested "before" and "after" lines may be output.
Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater. BUFSIZ is defined in <stdio.h>.
When there is more than one pattern (specified by the use of -e and/or -f), each pattern is applied to each line
in the order in which they are defined, except that all the -e patterns are tried before the -f patterns.
By default, as soon as one pattern matches a line, no further patterns are considered. However, if --colour (or
--color) is used to colour the matching substrings, or if --only-matching, --file-offsets, --line-offsets, or
--output is used to output only the part of the line that matched (either shown literally, or as an offset), the
behaviour is different. In this situation, all the patterns are applied to the line. If there is more than one
match, the one that begins nearest to the start of the subject is processed; if there is more than one match at
that position, the one with the longest matching substring is processed; if the matching substrings are equal,
the first match found is processed.
Scanning with all the patterns resumes immediately following the match, so that later matches on the same line
can be found. Note, however, that an overlapping match that starts in the middle of another match will not be
processed.
The above behaviour was changed at release 10.41 to be more compatible with GNU grep. In earlier releases,
pcre2grep did not recognize matches from later patterns that were earlier in the subject.
Patterns that can match an empty string are accepted, but empty string matches are never recognized. An example
is the pattern "(super)?(man)?", in which all components are optional. This pattern finds all occurrences of both
"super" and "man"; the output differs from matching with "super|man" when only the matching substrings are being
shown.
If the LC_ALL or LC_CTYPE environment variable is set, pcre2grep uses the value to set a locale when calling the
PCRE2 library. The --locale option can be used to override this.
SUPPORT FOR COMPRESSED FILES
Compile-time options for pcre2grep can set it up to use libz or libbz2 for reading compressed files whose names
end in .gz or .bz2, respectively. You can find out whether your pcre2grep binary has support for one or both of
these file types by running it with the --help option. If the appropriate support is not present, all files are
treated as plain text. The standard input is always so treated. If a file with a .gz or .bz2 extension is not in
fact compressed, it is read as a plain text file. When input is from a compressed .gz or .bz2 file, the --line-
buffered option is ignored.
BINARY FILES
By default, a file that contains a binary zero byte within the first 1024 bytes is identified as a binary file,
and is processed specially. However, if the newline type is specified as NUL, that is, the line terminator is a
binary zero, the test for a binary file is not applied. See the --binary-files option for a means of changing the
way binary files are handled.
BINARY ZEROS IN PATTERNS
Patterns passed from the command line are strings that are terminated by a binary zero, so cannot contain inter‐
nal 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 af‐
fect 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 con‐
text lines (the -Z option can be used to change the file name terminator to a zero byte). A line con‐
taining "--" 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 us‐
age.
-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 ig‐
nored.
--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 suc‐
ceeds. 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 bi‐
nary garbage, which can have nasty effects if sent to a terminal. If the word is "without-match", which
is equivalent to the -I option, binary files are not processed at all; they are assumed not to be of
interest and are skipped without causing any output or affecting the return code.
--buffer-size=number
Set the parameter that controls how much memory is obtained at the start of processing for buffering
files that are being scanned. See also --max-buffer-size below.
-C number, --context=number
Output number lines of context both before and after each matching line. This is equivalent to setting
both -A and -B to the same value.
-c, --count
Do not output lines from the files that are being scanned; instead output the number of lines that
would have been shown, either because they matched, or, if -v is set, because they failed to match. By
default, this count is exactly the same as the number of lines that would have been output, but if the
-M (multiline) option is used (without -v), there may be more suppressed lines than the count (that is,
the number of matches).
If no lines are selected, the number zero is output. If several files are are being scanned, a count is
output for each of them and the -t option can be used to cause a total to be output at the end. How‐
ever, 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 de‐
fault, 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 con‐
nected to a terminal. More resources are used when colouring is enabled, because pcre2grep has to
search for all possible matches in a line, not just one, in order to colour them all.
The colour that is used can be specified by setting one of the environment variables PCRE2GREP_COLOUR,
PCRE2GREP_COLOR, PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that order. If none of these
are set, pcre2grep looks for GREP_COLORS or GREP_COLOR (in that order). The value of the variable
should be a string of two numbers, separated by a semicolon, except in the case of GREP_COLORS, which
must start with "ms=" or "mt=" followed by two semicolon-separated colours, terminated by the end of
the string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is ignored, and
GREP_COLOR is checked.
If the string obtained from one of the above variables contains any characters other than semicolon or
digits, the setting is ignored and the default colour is used. The string is copied directly into the
control string for setting colour on a terminal, so it is your responsibility to ensure that the values
make sense. If no relevant environment variable is set, the default is "1;31", which gives red.
-D action, --devices=action
If an input path is not a regular file or a directory, "action" specifies how it is to be processed.
Valid values are "read" (the default) or "skip" (silently skip the path).
-d action, --directories=action
If an input path is a directory, "action" specifies how it is to be processed. Valid values are "read"
(the default in non-Windows environments, for compatibility with GNU grep), "recurse" (equivalent to
the -r option), or "skip" (silently skip the path, the default in Windows environments). In the "read"
case, directories are read as if they were ordinary files. In some operating systems the effect of
reading a directory like this is an immediate end-of-file; in others it may provoke an error.
--depth-limit=number
See --match-limit below.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used multiple times in order to specify several
patterns. It can also be used as a way of specifying a single pattern that starts with a hyphen. When
-e is used, no argument pattern is taken from the command line; all arguments are treated as file
names. There is no limit to the number of patterns. They are applied to each line in the order in which
they are defined.
If -f is used with -e, the command line patterns are matched first, followed by the patterns from the
file(s), independent of the order in which these options are specified.
--exclude=pattern
Files (but not directories) whose names match the pattern are skipped without being processed. This ap‐
plies to all files, whether listed on the command line, obtained from --file-list, or by scanning a di‐
rectory. 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 op‐
tion. 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 op‐
tions 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 delim‐
iters should be used. What constitutes a newline when reading the file is the operating system's de‐
fault interpretation of \n. The --newline option has no effect on this option. Trailing white space is
removed from each line, and blank lines are ignored. An empty file contains no patterns and therefore
matches nothing. Patterns read from a file in this way may contain binary zeros, which are treated as
ordinary data characters.
If this option is given more than once, all the specified files are read. A data line is output if any
of the patterns match it. A file name can be given as "-" to refer to the standard input. When -f is
used, patterns specified on the command line using -e may also be present; they are matched before the
file's patterns. However, no pattern is taken from the command line; all arguments are treated as the
names of paths to be searched.
--file-list=filename
Read a list of files and/or directories that are to be scanned from the given file, one per line. What
constitutes a newline when reading the file is the operating system's default. Trailing white space is
removed from each line, and blank lines are ignored. These paths are processed before any that are
listed on the command line. The file name can be given as "-" to refer to the standard input. If --file
and --file-list are both specified as "-", patterns are read first. This is useful only when the stan‐
dard input is a terminal, from which further lines (the list of files) can be read after an end-of-file
indication. If this option is given more than once, all the specified files are read.
--file-offsets
Instead of showing lines or parts of lines that match, show each match as an offset from the start of
the file and a length, separated by a comma. In this mode, --colour has no effect, and no context is
shown. That is, the -A, -B, and -C options are ignored. If there is more than one match in a line, each
of them is shown separately. This option is mutually exclusive with --output, --line-offsets, and
--only-matching.
-H, --with-filename
Force the inclusion of the file name at the start of output lines when searching a single file. The
file name is not normally shown in this case. By default, for matching lines, the file name is fol‐
lowed 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 multi‐
ple files are searched. By default, for matching lines, the file name is followed by a colon; for con‐
text 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 pre‐
vious -H, -L, or -l options.
--heap-limit=number
See --match-limit below.
--help Output a help message, giving brief details of the command options and file type support, and then
exit. Anything else on the command line is ignored.
-I Ignore binary files. This is equivalent to --binary-files=without-match.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
If any --include patterns are specified, the only files that are processed are those whose names match
one of the patterns and do not match an --exclude pattern. This option does not affect directories, but
it applies to all files, whether listed on the command line, obtained from --file-list, or by scanning
a directory. The pattern is a PCRE2 regular expression, and is matched against the final component of
the file name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option
may be given any number of times. If a file name matches both an --include and an --exclude pattern, it
is excluded. There is no short form for this option.
--include-from=filename
Treat each non-empty line of the file as the data for an --include option. What constitutes a newline
for this purpose is the operating system's default. The --newline option has no effect on this option.
This option may be given any number of times; all the files are read.
--include-dir=pattern
If any --include-dir patterns are specified, the only directories that are processed are those whose
names match one of the patterns and do not match an --exclude-dir pattern. This applies to all directo‐
ries, 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 oc‐
curs 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 Win‐
dows. Output to terminal is normally automatically flushed by the operating system. This option can be
useful when the input or output is attached to a pipe and you do not want pcre2grep to buffer up large
amounts of data. However, its use will affect performance, and the -M (multiline) option ceases to
work. When input is from a compressed .gz or .bz2 file, --line-buffered is ignored.
--line-offsets
Instead of showing lines or parts of lines that match, show each match as a line number, the offset
from the start of the line, and a length. The line number is terminated by a colon (as usual; see the
-n option), and the offset and length are separated by a comma. In this mode, --colour has no effect,
and no context is shown. That is, the -A, -B, and -C options are ignored. If there is more than one
match in a line, each of them is shown separately. This option is mutually exclusive with --output,
--file-offsets, and --only-matching.
--locale=locale-name
This option specifies a locale to be used for pattern matching. It overrides the value in the LC_ALL or
LC_CTYPE environment variables. If no locale is specified, the PCRE2 library's default (usually the "C"
locale) is used. There is no short form for this option.
-M, --multiline
Allow patterns to match more than one line. When this option is set, the PCRE2 library is called in
"multiline" mode. This allows a matched string to extend past the end of a line and continue on one or
more subsequent lines. Patterns used with -M may usefully contain literal newline characters and inter‐
nal occurrences of ^ and $ characters. The output for a successful match may consist of more than one
line. The first line is the line in which the match started, and the last line is the line in which the
match ended. If the matched string ends with a newline sequence, the output ends at the end of that
line. If -v is set, none of the lines in a multi-line match are output. Once a match has been handled,
scanning restarts at the beginning of the line after the one in which the match ended.
The newline sequence that separates multiple lines must be matched as part of the pattern. For example,
to find the phrase "regular expression" in a file where "regular" might be at the end of a line and
"expression" at the start of the next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, including newlines, and is followed by + so
as to match trailing white space on the first line as well as possibly handling a two-character newline
sequence.
There is a limit to the number of lines that can be matched, imposed by the way that pcre2grep buffers
the input file as it scans it. With a sufficiently large processing buffer, this should not be a prob‐
lem, 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 reg‐
ular 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 match‐
ing strings. Others may require a very large amount of memory. There are three options that set re‐
source 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 ap‐
ply to files specified by the -f, --exclude-from, or --include-from options, which are expected to use
the operating system's standard newline sequence.
-n, --line-number
Precede each output line by its line number in the file, followed by a colon for matching lines or a
hyphen for context lines. If the file name is also being output, it precedes the line number. When the
-M option causes a pattern to match more than one line, only the first is preceded by its line number.
This option is forced if --line-offsets is used.
--no-jit If the PCRE2 library is built with support for just-in-time compiling (which speeds up matching),
pcre2grep automatically makes use of this, unless it was explicitly disabled at build time. This option
can be used to disable the use of JIT at run time. It is provided for testing and working round 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, followed by an operating-system standard newline. In this mode, --colour has no effect,
and no context is shown. That is, the -A, -B, and -C options are ignored. The --newline option has no
effect on this option, which is mutually exclusive with --only-matching, --file-offsets, and --line-
offsets. However, like --only-matching, if there is more than one match in a line, each of them causes
a line of output.
Escape sequences starting with a dollar character may be used to insert the contents of the matched
part of the line and/or captured substrings into the text.
$<digits> or ${<digits>} is replaced by the captured substring of the given decimal number; zero sub‐
stitutes 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 con‐
text 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 speci‐
fied 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 cap‐
turing parentheses 3 and 1 and then 3 again to be output. By default, there is no separator (but see
the next but one option).
--om-capture=number
Set the number of capturing parentheses that can be accessed by -o. The default is 50.
--om-separator=text
Specify a separating string for multiple occurrences of -o. The default is an empty string. Separating
strings are never coloured.
-q, --quiet
Work quietly, that is, display nothing except error messages. The exit status indicates whether or not
any matches were found.
-r, --recursive
If any given path is a directory, recursively scan the files it contains, taking note of any --include
and --exclude settings. By default, a directory is read as a normal file; in some operating systems
this gives an immediate end-of-file. This option is a shorthand for setting the -d option to "recurse".
--recursion-limit=number
This is an obsolete synonym for --depth-limit. See --match-limit above for details.
-s, --no-messages
Suppress error messages about non-existent or unreadable files. Such files are quietly skipped. How‐
ever, the return code is still 2, even if matches were found in other files.
-t, --total-count
This option is useful when scanning more than one file. If used on its own, -t suppresses all output
except for a grand total number of matching lines (or non-matching lines if -v is used) in all the
files. If -t is used with -c, a grand total is output except when the previous output is just one line.
In other words, it is not output when just one file's count is listed. If file names are being output,
the grand total is preceded by "TOTAL:". Otherwise, it appears as just another number. The -t option is
ignored when used with -L (list files without matches), because the grand total would always be zero.
-u, --utf Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled with UTF-8 support. All
patterns (including those for any --exclude and --include options) and all lines that are scanned must
be valid strings of UTF-8 characters. If an invalid UTF-8 string is encountered, an error occurs.
-U, --utf-allow-invalid
As --utf, but in addition subject lines may contain invalid UTF-8 code unit sequences. These can never
form part of any pattern match. Patterns themselves, however, must still be valid UTF-8 strings. This
facility allows valid UTF-8 strings to be sought within arbitrary byte sequences in executable or other
binary files. For more details about matching in non-valid UTF-8 strings, see the pcre2unicode(3) docu‐
mentation.
-V, --version
Write the version numbers of pcre2grep and the PCRE2 library to the standard output and then exit. Any‐
thing 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 --in‐
clude 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 se‐
quences they have in the input. However, if the final line of a file is output, and it does not end with a new‐
line sequence, a newline sequence is added. If the newline setting is CR, LF, CRLF or NUL, that line ending is
output; for the other settings (ANYCRLF or ANY) a single NL is used.
The newline setting does not affect the way in which pcre2grep writes newlines in informational messages to the
standard output and error streams. Under Windows, the standard output is set to be binary, so that "\r\n" at the
ends of output lines that are copied from the input is not converted to "\r\r\n" by the C I/O library. This means
that any messages written to the standard output must end with "\r\n". For all other operating systems, and for
all messages to the standard error stream, "\n" is used.
OPTIONS COMPATIBILITY
Many of the short and long forms of pcre2grep's options are the same as in the GNU grep program. Any long option
of the form --xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE2 terminology). However, the
--depth-limit, --file-list, --file-offsets, --heap-limit, --include-dir, --line-offsets, --locale, --match-limit,
-M, --multiline, -N, --newline, --om-separator, --output, -u, --utf, -U, and --utf-allow-invalid options are spe‐
cific 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 --in‐
clude option's argument is a glob for GNU grep, but a regular expression for pcre2grep. If both the -c and -l op‐
tions 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 charac‐
ter, 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 op‐
tional. If one of these options does have data, it must be given in the first form, using an equals character.
Otherwise pcre2grep will assume that it has no data.
USING PCRE2'S CALLOUT FACILITY
pcre2grep has, by default, support for calling external programs or scripts or echoing specific strings during
matching by making use of PCRE2's callout facility. However, this support can be completely or partially disabled
when pcre2grep is built. You can find out whether your binary has support for callouts by running it with the
--help option. If callout support is completely disabled, all callouts in patterns are ignored by pcre2grep. If
the facility is partially disabled, calling external programs is not supported, and callouts that request it are
ignored.
A callout in a PCRE2 pattern is of the form (?C<arg>) where the argument is either a number or a quoted string
(see the pcre2callout documentation for details). Numbered callouts are ignored by pcre2grep; only callouts with
string arguments are useful.
Echoing a specific string
Starting the callout string with a pipe character invokes an echoing facility that avoids calling an external
program or script. This facility is always available, provided that callouts were not completely disabled when
pcre2grep was built. The rest of the callout string is processed as a zero-terminated string, which means it
should not contain any internal binary zeros. It is written to the output, having first been passed through the
same escape processing as text from the --output (-O) option (see above). However, $0 cannot be used to insert a
matched substring because the match is still in progress. Instead, the single character '0' is inserted. Any syn‐
tax errors in the string (for example, a dollar not followed by another character) causes the callout to be ig‐
nored. No terminator is added to the output string, so if you want a newline, you must include it explicitly us‐
ing 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 ex‐
ecv() 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 spec‐
ifying arguments:
executable_name|arg1|arg2|...
Any substring (including the executable name) may contain escape sequences started by a dollar character. These
are the same as for the --output (-O) option documented above, except that $0 cannot insert the matched string
because the match is still in progress. Instead, the character '0' is inserted. If you need a literal dollar or
pipe character in any substring, use $$ or $| respectively. Here is an example:
echo -e "abcde\n12345" | pcre2grep \
'(?x)(.)(..(.))
(?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
Output:
Arg1: [a] [bcd] [d] Arg2: |a| ()
abcde
Arg1: [1] [234] [4] Arg2: |1| ()
12345
The parameters for the system call that is used to run the program or script are zero-terminated strings. This
means that binary zero characters in the callout argument will cause premature termination of their substrings,
and therefore should not be present. Any syntax errors in the string (for example, a dollar not followed by an‐
other character) causes the callout to be ignored. If running the program fails for any reason (including the
non-existence of the executable), a local matching failure occurs and the matcher backtracks in the normal way.
MATCHING ERRORS
It is possible to supply a regular expression that takes a very long time to fail to match certain lines. Such
patterns normally involve nested indefinite repeats, for example: (a+)*\d when matched against a line of a's with
no final digit. The PCRE2 matching function has a resource limit that causes it to abort in these circumstances.
If this happens, pcre2grep outputs an error message and the line that caused the problem to the standard error
stream. If there are more than 20 such errors, pcre2grep gives up.
The --match-limit option of pcre2grep can be used to set the overall resource limit. There are also other limits
that affect the amount of memory used during matching; see the discussion of --heap-limit and --depth-limit
above.
DIAGNOSTICS
Exit status is 0 if any matches were found, 1 if no matches were found, and 2 for syntax errors, overlong lines,
non-existent or inaccessible files (even if matches were found in other files) or too many matching errors. Using
the -s option to suppress error messages about inaccessible files does not affect the return code.
When run under VMS, the return code is placed in the symbol PCRE2GREP_RC because VMS does not distinguish between
exit(0) and exit(1).
SEE ALSO
pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3).
AUTHOR
Philip Hazel
Retired from University Computing Service
Cambridge, England.
REVISION
Last updated: 21 November 2022
Copyright (c) 1997-2022 University of Cambridge.
PCRE2 10.41 21 November 2022 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. Each line that matches a pattern is copied to the standard
output, and if there is more than one file, the file name is output at the start of each line, followed by a
colon. However, there are options that can change how pcre2grep behaves. For example, the -M option makes it
possible to search for strings that span line boundaries. What defines a line boundary is controlled by the -N
(--newline) option. The -h and -H options control whether or not file names are shown, and the -Z option changes
the file name terminator to a zero byte.
The amount of memory used for buffering files that are being scanned is controlled by parameters that can be set
by the --buffer-size and --max-buffer-size options. The first of these sets the size of buffer that is obtained
at the start of processing. If an input file contains very long lines, a larger buffer may be needed; this is
handled by automatically extending the buffer, up to the limit specified by --max-buffer-size. The default values
for these parameters can be set when pcre2grep is built; if nothing is specified, the defaults are set to 20KiB
and 1MiB respectively. An error occurs if a line is too long and the buffer can no longer be expanded.
The block of memory that is actually used is three times the "buffer size", to allow for buffering "before" and
"after" lines. If the buffer size is too small, fewer than requested "before" and "after" lines may be output.
Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater. BUFSIZ is defined in <stdio.h>.
When there is more than one pattern (specified by the use of -e and/or -f), each pattern is applied to each line
in the order in which they are defined, except that all the -e patterns are tried before the -f patterns.
By default, as soon as one pattern matches a line, no further patterns are considered. However, if --colour (or
--color) is used to colour the matching substrings, or if --only-matching, --file-offsets, --line-offsets, or
--output is used to output only the part of the line that matched (either shown literally, or as an offset), the
behaviour is different. In this situation, all the patterns are applied to the line. If there is more than one
match, the one that begins nearest to the start of the subject is processed; if there is more than one match at
that position, the one with the longest matching substring is processed; if the matching substrings are equal,
the first match found is processed.
Scanning with all the patterns resumes immediately following the match, so that later matches on the same line
can be found. Note, however, that an overlapping match that starts in the middle of another match will not be
processed.
The above behaviour was changed at release 10.41 to be more compatible with GNU grep. In earlier releases,
pcre2grep did not recognize matches from later patterns that were earlier in the subject.
Patterns that can match an empty string are accepted, but empty string matches are never recognized. An example
is the pattern "(super)?(man)?", in which all components are optional. This pattern finds all occurrences of both
"super" and "man"; the output differs from matching with "super|man" when only the matching substrings are being
shown.
If the LC_ALL or LC_CTYPE environment variable is set, pcre2grep uses the value to set a locale when calling the
PCRE2 library. The --locale option can be used to override this.
SUPPORT FOR COMPRESSED FILES
Compile-time options for pcre2grep can set it up to use libz or libbz2 for reading compressed files whose names
end in .gz or .bz2, respectively. You can find out whether your pcre2grep binary has support for one or both of
these file types by running it with the --help option. If the appropriate support is not present, all files are
treated as plain text. The standard input is always so treated. If a file with a .gz or .bz2 extension is not in
fact compressed, it is read as a plain text file. When input is from a compressed .gz or .bz2 file, the --line-
buffered option is ignored.
BINARY FILES
By default, a file that contains a binary zero byte within the first 1024 bytes is identified as a binary file,
and is processed specially. However, if the newline type is specified as NUL, that is, the line terminator is a
binary zero, the test for a binary file is not applied. See the --binary-files option for a means of changing the
way binary files are handled.
BINARY ZEROS IN PATTERNS
Patterns passed from the command line are strings that are terminated by a binary zero, so cannot contain inter‐
nal 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 af‐
fect 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 con‐
text lines (the -Z option can be used to change the file name terminator to a zero byte). A line con‐
taining "--" 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 us‐
age.
-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 ig‐
nored.
--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 suc‐
ceeds. 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 bi‐
nary garbage, which can have nasty effects if sent to a terminal. If the word is "without-match", which
is equivalent to the -I option, binary files are not processed at all; they are assumed not to be of
interest and are skipped without causing any output or affecting the return code.
--buffer-size=number
Set the parameter that controls how much memory is obtained at the start of processing for buffering
files that are being scanned. See also --max-buffer-size below.
-C number, --context=number
Output number lines of context both before and after each matching line. This is equivalent to setting
both -A and -B to the same value.
-c, --count
Do not output lines from the files that are being scanned; instead output the number of lines that
would have been shown, either because they matched, or, if -v is set, because they failed to match. By
default, this count is exactly the same as the number of lines that would have been output, but if the
-M (multiline) option is used (without -v), there may be more suppressed lines than the count (that is,
the number of matches).
If no lines are selected, the number zero is output. If several files are are being scanned, a count is
output for each of them and the -t option can be used to cause a total to be output at the end. How‐
ever, 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 de‐
fault, 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 con‐
nected to a terminal. More resources are used when colouring is enabled, because pcre2grep has to
search for all possible matches in a line, not just one, in order to colour them all.
The colour that is used can be specified by setting one of the environment variables PCRE2GREP_COLOUR,
PCRE2GREP_COLOR, PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that order. If none of these
are set, pcre2grep looks for GREP_COLORS or GREP_COLOR (in that order). The value of the variable
should be a string of two numbers, separated by a semicolon, except in the case of GREP_COLORS, which
must start with "ms=" or "mt=" followed by two semicolon-separated colours, terminated by the end of
the string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is ignored, and
GREP_COLOR is checked.
If the string obtained from one of the above variables contains any characters other than semicolon or
digits, the setting is ignored and the default colour is used. The string is copied directly into the
control string for setting colour on a terminal, so it is your responsibility to ensure that the values
make sense. If no relevant environment variable is set, the default is "1;31", which gives red.
-D action, --devices=action
If an input path is not a regular file or a directory, "action" specifies how it is to be processed.
Valid values are "read" (the default) or "skip" (silently skip the path).
-d action, --directories=action
If an input path is a directory, "action" specifies how it is to be processed. Valid values are "read"
(the default in non-Windows environments, for compatibility with GNU grep), "recurse" (equivalent to
the -r option), or "skip" (silently skip the path, the default in Windows environments). In the "read"
case, directories are read as if they were ordinary files. In some operating systems the effect of
reading a directory like this is an immediate end-of-file; in others it may provoke an error.
--depth-limit=number
See --match-limit below.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used multiple times in order to specify several
patterns. It can also be used as a way of specifying a single pattern that starts with a hyphen. When
-e is used, no argument pattern is taken from the command line; all arguments are treated as file
names. There is no limit to the number of patterns. They are applied to each line in the order in which
they are defined.
If -f is used with -e, the command line patterns are matched first, followed by the patterns from the
file(s), independent of the order in which these options are specified.
--exclude=pattern
Files (but not directories) whose names match the pattern are skipped without being processed. This ap‐
plies to all files, whether listed on the command line, obtained from --file-list, or by scanning a di‐
rectory. 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 op‐
tion. 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 op‐
tions 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 delim‐
iters should be used. What constitutes a newline when reading the file is the operating system's de‐
fault interpretation of \n. The --newline option has no effect on this option. Trailing white space is
removed from each line, and blank lines are ignored. An empty file contains no patterns and therefore
matches nothing. Patterns read from a file in this way may contain binary zeros, which are treated as
ordinary data characters.
If this option is given more than once, all the specified files are read. A data line is output if any
of the patterns match it. A file name can be given as "-" to refer to the standard input. When -f is
used, patterns specified on the command line using -e may also be present; they are matched before the
file's patterns. However, no pattern is taken from the command line; all arguments are treated as the
names of paths to be searched.
--file-list=filename
Read a list of files and/or directories that are to be scanned from the given file, one per line. What
constitutes a newline when reading the file is the operating system's default. Trailing white space is
removed from each line, and blank lines are ignored. These paths are processed before any that are
listed on the command line. The file name can be given as "-" to refer to the standard input. If --file
and --file-list are both specified as "-", patterns are read first. This is useful only when the stan‐
dard input is a terminal, from which further lines (the list of files) can be read after an end-of-file
indication. If this option is given more than once, all the specified files are read.
--file-offsets
Instead of showing lines or parts of lines that match, show each match as an offset from the start of
the file and a length, separated by a comma. In this mode, --colour has no effect, and no context is
shown. That is, the -A, -B, and -C options are ignored. If there is more than one match in a line, each
of them is shown separately. This option is mutually exclusive with --output, --line-offsets, and
--only-matching.
-H, --with-filename
Force the inclusion of the file name at the start of output lines when searching a single file. The
file name is not normally shown in this case. By default, for matching lines, the file name is fol‐
lowed 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 multi‐
ple files are searched. By default, for matching lines, the file name is followed by a colon; for con‐
text 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 pre‐
vious -H, -L, or -l options.
--heap-limit=number
See --match-limit below.
--help Output a help message, giving brief details of the command options and file type support, and then
exit. Anything else on the command line is ignored.
-I Ignore binary files. This is equivalent to --binary-files=without-match.
-i, --ignore-case
Ignore upper/lower case distinctions during comparisons.
--include=pattern
If any --include patterns are specified, the only files that are processed are those whose names match
one of the patterns and do not match an --exclude pattern. This option does not affect directories, but
it applies to all files, whether listed on the command line, obtained from --file-list, or by scanning
a directory. The pattern is a PCRE2 regular expression, and is matched against the final component of
the file name, not the entire path. The -F, -w, and -x options do not apply to this pattern. The option
may be given any number of times. If a file name matches both an --include and an --exclude pattern, it
is excluded. There is no short form for this option.
--include-from=filename
Treat each non-empty line of the file as the data for an --include option. What constitutes a newline
for this purpose is the operating system's default. The --newline option has no effect on this option.
This option may be given any number of times; all the files are read.
--include-dir=pattern
If any --include-dir patterns are specified, the only directories that are processed are those whose
names match one of the patterns and do not match an --exclude-dir pattern. This applies to all directo‐
ries, 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 oc‐
curs 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 Win‐
dows. Output to terminal is normally automatically flushed by the operating system. This option can be
useful when the input or output is attached to a pipe and you do not want pcre2grep to buffer up large
amounts of data. However, its use will affect performance, and the -M (multiline) option ceases to
work. When input is from a compressed .gz or .bz2 file, --line-buffered is ignored.
--line-offsets
Instead of showing lines or parts of lines that match, show each match as a line number, the offset
from the start of the line, and a length. The line number is terminated by a colon (as usual; see the
-n option), and the offset and length are separated by a comma. In this mode, --colour has no effect,
and no context is shown. That is, the -A, -B, and -C options are ignored. If there is more than one
match in a line, each of them is shown separately. This option is mutually exclusive with --output,
--file-offsets, and --only-matching.
--locale=locale-name
This option specifies a locale to be used for pattern matching. It overrides the value in the LC_ALL or
LC_CTYPE environment variables. If no locale is specified, the PCRE2 library's default (usually the "C"
locale) is used. There is no short form for this option.
-M, --multiline
Allow patterns to match more than one line. When this option is set, the PCRE2 library is called in
"multiline" mode. This allows a matched string to extend past the end of a line and continue on one or
more subsequent lines. Patterns used with -M may usefully contain literal newline characters and inter‐
nal occurrences of ^ and $ characters. The output for a successful match may consist of more than one
line. The first line is the line in which the match started, and the last line is the line in which the
match ended. If the matched string ends with a newline sequence, the output ends at the end of that
line. If -v is set, none of the lines in a multi-line match are output. Once a match has been handled,
scanning restarts at the beginning of the line after the one in which the match ended.
The newline sequence that separates multiple lines must be matched as part of the pattern. For example,
to find the phrase "regular expression" in a file where "regular" might be at the end of a line and
"expression" at the start of the next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, including newlines, and is followed by + so
as to match trailing white space on the first line as well as possibly handling a two-character newline
sequence.
There is a limit to the number of lines that can be matched, imposed by the way that pcre2grep buffers
the input file as it scans it. With a sufficiently large processing buffer, this should not be a prob‐
lem, 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 reg‐
ular 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 match‐
ing strings. Others may require a very large amount of memory. There are three options that set re‐
source 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 ap‐
ply to files specified by the -f, --exclude-from, or --include-from options, which are expected to use
the operating system's standard newline sequence.
-n, --line-number
Precede each output line by its line number in the file, followed by a colon for matching lines or a
hyphen for context lines. If the file name is also being output, it precedes the line number. When the
-M option causes a pattern to match more than one line, only the first is preceded by its line number.
This option is forced if --line-offsets is used.
--no-jit If the PCRE2 library is built with support for just-in-time compiling (which speeds up matching),
pcre2grep automatically makes use of this, unless it was explicitly disabled at build time. This option
can be used to disable the use of JIT at run time. It is provided for testing and working round 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, followed by an operating-system standard newline. In this mode, --colour has no effect,
and no context is shown. That is, the -A, -B, and -C options are ignored. The --newline option has no
effect on this option, which is mutually exclusive with --only-matching, --file-offsets, and --line-
offsets. However, like --only-matching, if there is more than one match in a line, each of them causes
a line of output.
Escape sequences starting with a dollar character may be used to insert the contents of the matched
part of the line and/or captured substrings into the text.
$<digits> or ${<digits>} is replaced by the captured substring of the given decimal number; zero sub‐
stitutes 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 con‐
text 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 speci‐
fied 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 cap‐
turing parentheses 3 and 1 and then 3 again to be output. By default, there is no separator (but see
the next but one option).
--om-capture=number
Set the number of capturing parentheses that can be accessed by -o. The default is 50.
--om-separator=text
Specify a separating string for multiple occurrences of -o. The default is an empty string. Separating
strings are never coloured.
-q, --quiet
Work quietly, that is, display nothing except error messages. The exit status indicates whether or not
any matches were found.
-r, --recursive
If any given path is a directory, recursively scan the files it contains, taking note of any --include
and --exclude settings. By default, a directory is read as a normal file; in some operating systems
this gives an immediate end-of-file. This option is a shorthand for setting the -d option to "recurse".
--recursion-limit=number
This is an obsolete synonym for --depth-limit. See --match-limit above for details.
-s, --no-messages
Suppress error messages about non-existent or unreadable files. Such files are quietly skipped. How‐
ever, the return code is still 2, even if matches were found in other files.
-t, --total-count
This option is useful when scanning more than one file. If used on its own, -t suppresses all output
except for a grand total number of matching lines (or non-matching lines if -v is used) in all the
files. If -t is used with -c, a grand total is output except when the previous output is just one line.
In other words, it is not output when just one file's count is listed. If file names are being output,
the grand total is preceded by "TOTAL:". Otherwise, it appears as just another number. The -t option is
ignored when used with -L (list files without matches), because the grand total would always be zero.
-u, --utf Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled with UTF-8 support. All
patterns (including those for any --exclude and --include options) and all lines that are scanned must
be valid strings of UTF-8 characters. If an invalid UTF-8 string is encountered, an error occurs.
-U, --utf-allow-invalid
As --utf, but in addition subject lines may contain invalid UTF-8 code unit sequences. These can never
form part of any pattern match. Patterns themselves, however, must still be valid UTF-8 strings. This
facility allows valid UTF-8 strings to be sought within arbitrary byte sequences in executable or other
binary files. For more details about matching in non-valid UTF-8 strings, see the pcre2unicode(3) docu‐
mentation.
-V, --version
Write the version numbers of pcre2grep and the PCRE2 library to the standard output and then exit. Any‐
thing 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 --in‐
clude 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 se‐
quences they have in the input. However, if the final line of a file is output, and it does not end with a new‐
line sequence, a newline sequence is added. If the newline setting is CR, LF, CRLF or NUL, that line ending is
output; for the other settings (ANYCRLF or ANY) a single NL is used.
The newline setting does not affect the way in which pcre2grep writes newlines in informational messages to the
standard output and error streams. Under Windows, the standard output is set to be binary, so that "\r\n" at the
ends of output lines that are copied from the input is not converted to "\r\r\n" by the C I/O library. This means
that any messages written to the standard output must end with "\r\n". For all other operating systems, and for
all messages to the standard error stream, "\n" is used.
OPTIONS COMPATIBILITY
Many of the short and long forms of pcre2grep's options are the same as in the GNU grep program. Any long option
of the form --xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE2 terminology). However, the
--depth-limit, --file-list, --file-offsets, --heap-limit, --include-dir, --line-offsets, --locale, --match-limit,
-M, --multiline, -N, --newline, --om-separator, --output, -u, --utf, -U, and --utf-allow-invalid options are spe‐
cific 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 --in‐
clude option's argument is a glob for GNU grep, but a regular expression for pcre2grep. If both the -c and -l op‐
tions 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 charac‐
ter, 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 op‐
tional. If one of these options does have data, it must be given in the first form, using an equals character.
Otherwise pcre2grep will assume that it has no data.
USING PCRE2'S CALLOUT FACILITY
pcre2grep has, by default, support for calling external programs or scripts or echoing specific strings during
matching by making use of PCRE2's callout facility. However, this support can be completely or partially disabled
when pcre2grep is built. You can find out whether your binary has support for callouts by running it with the
--help option. If callout support is completely disabled, all callouts in patterns are ignored by pcre2grep. If
the facility is partially disabled, calling external programs is not supported, and callouts that request it are
ignored.
A callout in a PCRE2 pattern is of the form (?C<arg>) where the argument is either a number or a quoted string
(see the pcre2callout documentation for details). Numbered callouts are ignored by pcre2grep; only callouts with
string arguments are useful.
Echoing a specific string
Starting the callout string with a pipe character invokes an echoing facility that avoids calling an external
program or script. This facility is always available, provided that callouts were not completely disabled when
pcre2grep was built. The rest of the callout string is processed as a zero-terminated string, which means it
should not contain any internal binary zeros. It is written to the output, having first been passed through the
same escape processing as text from the --output (-O) option (see above). However, $0 cannot be used to insert a
matched substring because the match is still in progress. Instead, the single character '0' is inserted. Any syn‐
tax errors in the string (for example, a dollar not followed by another character) causes the callout to be ig‐
nored. No terminator is added to the output string, so if you want a newline, you must include it explicitly us‐
ing 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 ex‐
ecv() 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 spec‐
ifying arguments:
executable_name|arg1|arg2|...
Any substring (including the executable name) may contain escape sequences started by a dollar character. These
are the same as for the --output (-O) option documented above, except that $0 cannot insert the matched string
because the match is still in progress. Instead, the character '0' is inserted. If you need a literal dollar or
pipe character in any substring, use $$ or $| respectively. Here is an example:
echo -e "abcde\n12345" | pcre2grep \
'(?x)(.)(..(.))
(?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
Output:
Arg1: [a] [bcd] [d] Arg2: |a| ()
abcde
Arg1: [1] [234] [4] Arg2: |1| ()
12345
The parameters for the system call that is used to run the program or script are zero-terminated strings. This
means that binary zero characters in the callout argument will cause premature termination of their substrings,
and therefore should not be present. Any syntax errors in the string (for example, a dollar not followed by an‐
other character) causes the callout to be ignored. If running the program fails for any reason (including the
non-existence of the executable), a local matching failure occurs and the matcher backtracks in the normal way.
MATCHING ERRORS
It is possible to supply a regular expression that takes a very long time to fail to match certain lines. Such
patterns normally involve nested indefinite repeats, for example: (a+)*\d when matched against a line of a's with
no final digit. The PCRE2 matching function has a resource limit that causes it to abort in these circumstances.
If this happens, pcre2grep outputs an error message and the line that caused the problem to the standard error
stream. If there are more than 20 such errors, pcre2grep gives up.
The --match-limit option of pcre2grep can be used to set the overall resource limit. There are also other limits
that affect the amount of memory used during matching; see the discussion of --heap-limit and --depth-limit
above.
DIAGNOSTICS
Exit status is 0 if any matches were found, 1 if no matches were found, and 2 for syntax errors, overlong lines,
non-existent or inaccessible files (even if matches were found in other files) or too many matching errors. Using
the -s option to suppress error messages about inaccessible files does not affect the return code.
When run under VMS, the return code is placed in the symbol PCRE2GREP_RC because VMS does not distinguish between
exit(0) and exit(1).
SEE ALSO
pcre2pattern(3), pcre2syntax(3), pcre2callout(3), pcre2unicode(3).
AUTHOR
Philip Hazel
Retired from University Computing Service
Cambridge, England.
REVISION
Last updated: 21 November 2022
Copyright (c) 1997-2022 University of Cambridge.
PCRE2 10.41 21 November 2022 PCRE2GREP(1)