pcre2grep — a grep with Perl-compatible regular expressions.
pcre2grep [options] [long options]
[pattern] [path1 path2 ...]
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
Input files are searched line by line. By default, 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. In
particular, 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 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
,
or −−line−offsets
is used to
output only the part of the line that matched (either shown
literally, or as an offset), scanning resumes immediately
following the match, so that further matches on the same line
can be found. If there are multiple patterns, they are all
tried on the remainder of the line, but patterns that follow
the one that matched are not tried on the earlier matched
part of the line.
This behaviour means that the order in which multiple patterns are specified can affect the output when one of the above options is used. This is no longer the same behaviour as GNU grep, which now manages to display earlier matches for later patterns (as long as there is no overlap).
Patterns that can match an empty string are accepted, but empty string matches are never recognized. An example is the pattern "(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.
It is possible to compile pcre2grep so that it uses
libz or
libbz2 to read
compressed files whose names end in .gz
or .bz2
, respectively. You can
find out whether your pcre2grep binary has
support for one or both of these file types by running it
with the −−help
option. If the appropriate support is not present, all files
are treated as plain text. The standard input is always so
treated. When input is from a compressed .gz or .bz2 file,
the −−line−buffered
option is
ignored.
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.
Patterns passed from the command line are strings that are
terminated by a binary zero, so cannot contain internal
zeros. However, patterns that are read from a file via the
−f
option may contain
binary zeros.
The order in which some of the options appear can affect
the output. For example, both the −H
and −l
options affect the printing of file
names. Whichever comes later in the command line will be the
one that takes effect. Similarly, except where noted below,
if an option is given twice, the later setting is used.
Numerical values for options may be followed by K or M, to
signify multiplication by 1024 or 1024*1024 respectively.
−−
This terminates the list of options. It is useful if the next item on the command line starts with a hyphen but is not an option. This allows for the processing of patterns and file names that start with hyphens.
−A
number, −−after−context=
numberOutput up to number lines of
context after each matching line. Fewer lines are
output if the next match or the end of the file is
reached, or if the processing buffer size has been set
too small. If file names and/or line numbers are being
output, a hyphen separator is used instead of a colon
for the context lines. A line containing "--" is output
between each group of lines, unless they are in fact
contiguous in the input file. The value of number is expected to
be relatively small. When −c
is used, −A
is ignored.
−a
, −−text
Treat binary files as text. This is equivalent to
−−binary−files
=text.
−B
number, −−before−context=
numberOutput 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. A line containing "--" is output between
each group of lines, unless they are in fact contiguous
in the input file. The value of number is expected to
be relatively small. When −c
is used, −B
is ignored.
−−binary−files=
wordSpecify how binary files are to be processed. If the
word is "binary" (the default), pattern matching is
performed on binary files, but the only output is
"Binary file <name> matches" when a match
succeeds. If the word is "text", which is equivalent to
the −a
or
−−text
option,
binary files are processed in the same way as any other
file. In this case, when a match succeeds, the output
may be binary garbage, which can have nasty effects if
sent to a terminal. If the word is "without-match",
which is equivalent to the −I
option, binary files are not
processed at all; they are assumed not to be of
interest and are skipped without causing any output or
affecting the return code.
−−buffer−size=
numberSet 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=
numberOutput number lines of
context both before and after each matching line. This
is equivalent to setting both −A
and −B
to the same value.
−c
, −−count
Do not output lines from the files that are being
scanned; instead output the number of lines that would
have been shown, either because they matched, or, if
−v
is set, because
they failed to match. By default, this count is exactly
the same as the number of lines that would have been
output, but if the −M
(multiline) option is used (without −v
), there may be more suppressed
lines than the count (that is, the number of
matches).
If no lines are selected, the number zero is output.
If several files are are being scanned, a count is
output for each of them and the −t
option can be used to cause a
total to be output at the end. However, if the
−−files−with−matches
option is also used, only those files whose counts are
greater than zero are listed. When −c
is used, the −A
, −B
, and −C
options are ignored.
−−colour
, −−color
If this option is given without any data, it is equivalent to "--colour=auto". If data is required, it must be given in the same shell item, separated by an equals sign.
−−colour=
value, −−color=
valueThis option specifies under what circumstances the parts of a line that matched a pattern should be coloured in the output. By default, the output is not coloured. The value (which is optional, see above) may be "never", "always", or "auto". In the latter case, colouring happens only if the standard output is connected to a terminal. More resources are used when colouring is enabled, because pcre2grep has to search for all possible matches in a line, not just one, in order to colour them all.
The colour that is used can be specified by setting one of the environment variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR, PCREGREP_COLOUR, or PCREGREP_COLOR, which are checked in that order. If none of these are set, pcre2grep looks for GREP_COLORS or GREP_COLOR (in that order). The value of the variable should be a string of two numbers, separated by a semicolon, except in the case of GREP_COLORS, which must start with "ms=" or "mt=" followed by two semicolon-separated colours, terminated by the end of the string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is ignored, and GREP_COLOR is checked.
If the string obtained from one of the above variables contains any characters other than semicolon or digits, the setting is ignored and the default colour is used. The string is copied directly into the control string for setting colour on a terminal, so it is your responsibility to ensure that the values make sense. If no relevant environment variable is set, the default is "1;31", which gives red.
−D
action, −−devices=
actionIf 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=
actionIf 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
=numberSee −−match−limit
below.
−e
pattern, −−regex=
pattern, −−regexp=
patternSpecify 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 until one
matches.
If −f
is used with
−e
, the command line
patterns are matched first, followed by the patterns
from the file(s), independent of the order in which
these options are specified. Note that multiple use of
−e
is not the same as
a single pattern with alternatives. For example, X|Y
finds the first character in a line that is X or Y,
whereas if the two patterns are given separately, with
X first, pcre2grep finds X if
it is present, even if it follows Y in the line. It
finds Y only if there is no X in the line. This matters
only if you are using −o
or −−colo(u)r
to show the
part(s) of the line that matched.
−−exclude
=patternFiles (but not directories) whose names match the
pattern are skipped without being processed. This
applies to all files, whether listed on the command
line, obtained from −−file−list
, or by
scanning a directory. The pattern is a PCRE2 regular
expression, and is matched against the final component
of the file name, not the entire path. The −F
, −w
, and −x
options do not apply to this
pattern. The option may be given any number of times in
order to specify multiple patterns. If a file name
matches both an −−include
and an
−−exclude
pattern, it is excluded. There is no short form for
this option.
−−exclude−from=
filenameTreat each non-empty line of the file as the data
for an −−exclude
option. What
constitutes a newline when reading the file is the
operating system's default. The −−newline
option has no
effect on this option. This option may be given more
than once in order to specify a number of files to
read.
−−exclude−dir
=patternDirectories whose names match the pattern are
skipped without being processed, whatever the setting
of the −−recursive
option. This
applies to all directories, whether listed on the
command line, obtained from −−file−list
, or by
scanning a parent directory. The pattern is a PCRE2
regular expression, and is matched against the final
component of the directory name, not the entire path.
The −F
, −w
, and −x
options do not apply to this
pattern. The option may be given any number of times in
order to specify more than one pattern. If a directory
matches both −−include−dir
and
−−exclude−dir
, it is
excluded. There is no short form for this option.
−F
, −−fixed−strings
Interpret each data-matching pattern as a list of
fixed strings, separated by newlines, instead of as a
regular expression. What constitutes a newline for this
purpose is controlled by the −−newline
option. The
−w
(match as a word)
and −x
(match whole
line) options can be used with −F
. They apply to each of the
fixed strings. A line is selected if any of the fixed
strings are found in it (subject to −w
or −x
, if present). This option
applies only to the patterns that are matched against
the contents of files; it does not apply to patterns
specified by any of the −−include
or −−exclude
options.
−f
filename, −−file=
filenameRead patterns from the file, one per line, and match
them against each line of input. As is the case with
patterns on the command line, no delimiters should be
used. What constitutes a newline when reading the file
is the operating system's default interpretation of \n.
The −−newline
option has no effect on this option. Trailing white
space is removed from each line, and blank lines are
ignored. An empty file contains no patterns and
therefore matches nothing. Patterns read from a file in
this way may contain binary zeros, which are treated as
ordinary data characters. See also the comments about
multiple patterns versus a single pattern with
alternatives in the description of −e
above.
If this option is given more than once, all the
specified files are read. A data line is output if any
of the patterns match it. A file name can be given as
"-" to refer to the standard input. When −f
is used, patterns specified on
the command line using −e
may also be present; they are
tested before the file's patterns. However, no other
pattern is taken from the command line; all arguments
are treated as the names of paths to be searched.
−−file−list
=filenameRead a list of files and/or directories that are to
be scanned from the given file, one per line. What
constitutes a newline when reading the file is the
operating system's default. Trailing white space is
removed from each line, and blank lines are ignored.
These paths are processed before any that are listed on
the command line. The file name can be given as "-" to
refer to the standard input. If −−file
and −−file−list
are both
specified as "-", patterns are read first. This is
useful only when the standard input is a terminal, from
which further lines (the list of files) can be read
after an end-of-file indication. If this option is
given more than once, all the specified files are
read.
−−file−offsets
Instead of showing lines or parts of lines that
match, show each match as an offset from the start of
the file and a length, separated by a comma. In this
mode, 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. By default,
the file name is not shown in this case. For matching
lines, the file name is followed by a colon; for
context lines, a hyphen separator is used. 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. By default, file names are shown when
multiple files are searched. For matching lines, the
file name is followed by a colon; for context lines, a
hyphen separator is used. If a line number is also
being output, it follows the file name. This option
overrides any previous −H
, −L
, or −l
options.
−−heap−limit
=numberSee −−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
=patternIf 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=
filenameTreat 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
=patternIf any −−include−dir
patterns are specified, the only directories that are
processed are those whose names match one of the
patterns and do not match an −−exclude−dir
pattern. This applies to all directories, whether
listed on the command line, obtained from −−file−list
, or by
scanning a parent directory. The pattern is a PCRE2
regular expression, and is matched against the final
component of the directory name, not the entire path.
The −F
, −w
, and −x
options do not apply to this
pattern. The option may be given any number of times.
If a directory matches both −−include−dir
and
−−exclude−dir
, it is
excluded. There is no short form for this option.
−L
, −−files−without−match
Instead of outputting lines from the files, just
output the names of the files that do not contain any
lines that would have been output. Each file name is
output once, on a separate line. 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. Searching normally stops as soon as
a matching line is found in a file. However, if the
−c
(count) option is
also used, matching continues in order to obtain the
correct count, and those files that have at least one
match are listed along with their counts. Using this
option with −c
is a
way of suppressing the listing of files with no matches
that occurs with −c
on its own. This option overrides any previous
−H
, −h
, or −L
options.
−−label
=nameThis option supplies a name to be used for the standard input when file names are being output. If not supplied, "(standard input)" is used. There is no short form for this option.
−−line−buffered
When this option is given, non-compressed input is
read and processed line by line, and the output is
flushed after each write. By default, input is read in
large chunks, unless pcre2grep can
determine that it is reading from a terminal, which is
currently possible only in Unix-like environments or
Windows. Output to terminal is normally automatically
flushed by the operating system. This option can be
useful when the input or output is attached to a pipe
and you do not want pcre2grep to buffer
up large amounts of data. However, its use will affect
performance, and the −M
(multiline) option ceases to
work. When input is from a compressed .gz or .bz2 file,
−−line−buffered
is
ignored.
−−line−offsets
Instead of showing lines or parts of lines that
match, show each match as a line number, the offset
from the start of the line, and a length. The line
number is terminated by a colon (as usual; see the
−n
option), and the
offset and length are separated by a comma. In this
mode, no context is shown. That is, the −A
, −B
, and −C
options are ignored. If there
is more than one match in a line, each of them is shown
separately. This option is mutually exclusive with
−−output
,
−−file−offsets
, and
−−only−matching
.
−−locale
=locale-name
This option specifies a locale to be used for
pattern matching. It overrides the value in the
LC_ALL
or LC_CTYPE
environment variables. If no
locale is specified, the PCRE2 library's default
(usually the "C" locale) is used. There is no short
form for this option.
−M
, −−multiline
Allow patterns to match more than one line. When
this option is set, the PCRE2 library is called in
"multiline" mode. This allows a matched string to
extend past the end of a line and continue on one or
more subsequent lines. Patterns used with −M
may usefully contain literal
newline characters and internal occurrences of ^ and $
characters. The output for a successful match may
consist of more than one line. The first line is the
line in which the match started, and the last line is
the line in which the match ended. If the matched
string ends with a newline sequence, the output ends at
the end of that line. If −v
is set, none of the lines in a
multi-line match are output. Once a match has been
handled, scanning restarts at the beginning of the line
after the one in which the match ended.
The newline sequence that separates multiple lines must be matched as part of the pattern. For example, to find the phrase "regular expression" in a file where "regular" might be at the end of a line and "expression" at the start of the next line, you could use this command:
pcre2grep -M 'regular\s+expression' <file>
The \s escape sequence matches any white space character, including newlines, and is followed by + so as to match trailing white space on the first line as well as possibly handling a two-character newline sequence.
There is a limit to the number of lines that can be
matched, imposed by the way that pcre2grep buffers the
input file as it scans it. With a sufficiently large
processing buffer, this should not be a problem, but
the −M
option does
not work when input is read line by line (see
−−line−buffered
.)
−m
number, −−max−count
=numberStop processing after finding number matching
lines, or non-matching lines if −v
is also set. Any trailing
context lines are output after the final match. In
multiline mode, each multiline match counts as just one
line for this purpose. If this limit is reached when
reading the standard input from a regular file, the
file is left positioned just after the last matching
line. If −c
is also
set, the count that is output is never greater than
number.
This option has no effect if used with −L
, −l
, or −q
, or when just checking for a
match in a binary file.
−−match−limit
=numberProcessing some regular expression patterns may take a very long time to search for all possible matching strings. Others may require a very large amount of memory. There are three options that set resource limits for matching.
The −−match−limit
option
provides a means of limiting computing resource usage
when processing patterns that are not going to match,
but which have a very large number of possibilities in
their search trees. The classic example is a pattern
that uses nested unlimited repeats. Internally, PCRE2
has a counter that is incremented each time around its
main processing loop. If the value set by −−match−limit
is
reached, an error occurs.
The −−heap−limit
option
specifies, as a number of kibibytes (units of 1024
bytes), the amount of heap memory that may be used for
matching. Heap memory is needed only if matching the
pattern requires a significant number of nested
backtracking points to be remembered. This parameter
can be set to zero to forbid the use of heap memory
altogether.
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
=numberThis limits the expansion of the processing buffer,
whose initial size can be set by −−buffer−size
. The
maximum buffer size is silently forced to be no smaller
than the starting buffer size.
−N
newline-type
,
−−newline
=newline-type
Six different conventions for indicating the ends of lines in scanned files are supported. For example:
pcre2grep -N CRLF 'some pattern' <file>
The newline type may be specified in upper, lower, or mixed case. If the newline type is NUL, lines are separated by binary zero characters. The other types are the single-character sequences CR (carriage return) and LF (linefeed), the two-character sequence CRLF, an "anycrlf" type, which recognizes any of the preceding three types, and an "any" type, for which any Unicode line ending sequence is assumed to end a line. The Unicode sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
When the PCRE2 library is built, a default line-ending sequence is specified. This is normally the standard sequence for the operating system. Unless otherwise specified by this option, pcre2grep uses the library's default.
This option makes it possible to use pcre2grep to scan
files that have come from other environments without
having to modify their line endings. If the data that
is being scanned does not agree with the convention set
by this option, pcre2grep may behave
in strange ways. Note that this option does not apply
to files specified by the −f
, −−exclude−from
, or
−−include−from
options, which are expected to use the operating
system's standard newline sequence.
−n
, −−line−number
Precede each output line by its line number in the
file, followed by a colon for matching lines or a
hyphen for context lines. If the file name is also
being output, it precedes the line number. When the
−M
option causes a
pattern to match more than one line, only the first is
preceded by its line number. This option is forced if
−−line−offsets
is
used.
−−no−jit
If the PCRE2 library is built with support for just-in-time compiling (which speeds up matching), pcre2grep automatically makes use of this, unless it was explicitly disabled at build time. This option can be used to disable the use of JIT at run time. It is provided for testing and working round problems. It should never be needed in normal use.
−O
text, −−output
=textWhen 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, no context is shown. That is,
the −A
, −B
, and −C
options are ignored. The
−−newline
option has no effect on this option, which is mutually
exclusive with −−only−matching
,
−−file−offsets
, and
−−line−offsets
.
However, like −−only−matching
, if
there is more than one match in a line, each of them
causes a line of output.
Escape sequences starting with a dollar character may be used to insert the contents of the matched part of the line and/or captured substrings into the text.
$<digits> or ${<digits>} is replaced by the captured substring of the given decimal number; zero substitutes the whole match. If the number is greater than the number of capturing substrings, or if the capture is unset, the replacement is empty.
$a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by newline; $r by carriage return; $t by tab; $v by vertical tab.
$o<digits> or $o{<digits>} is replaced by the character whose code point is the given octal number. In the first form, up to three octal digits are processed. When more digits are needed in Unicode mode to specify a wide character, the second form must be used.
$x<digits> or $x{<digits>} is replaced by the character represented by the given hexadecimal number. In the first form, up to two hexadecimal digits are processed. When more digits are needed in Unicode mode to specify a wide character, the second form must be used.
Any other character is substituted by itself. In particular, $$ is replaced by a single dollar.
−o
, −−only−matching
Show only the part of the line that matched a
pattern instead of the whole line. In this mode, no
context is shown. That is, the −A
, −B
, and −C
options are ignored. If there
is more than one match in a line, each of them is shown
separately, on a separate line of output. If
−o
is combined with
−v
(invert the sense
of the match to find non-matching lines), no output is
generated, but the return code is set appropriately. If
the matched portion of the line is empty, nothing is
output unless the file name or line number are being
printed, in which case they are shown on an otherwise
empty line. This option is mutually exclusive with
−−output
,
−−file−offsets
and
−−line−offsets
.
−o
number, −−only−matching
=numberShow only the part of the line that matched the
capturing parentheses of the given number. Up to 50
capturing parentheses are supported by default. This
limit can be changed via the −−om−capture
option.
A pattern may contain any number of capturing
parentheses, but only those whose number is within the
limit can be accessed by −o
. An error occurs if the number
specified by −o
is
greater than the limit.
-o0 is the same as −o
without a number. Because
these options can be given without an argument (see
above), if an argument is present, it must be given in
the same shell item, for example, -o3 or
--only-matching=2. The comments given for the
non-argument case above also apply to this option. If
the specified capturing parentheses do not exist in the
pattern, or were not set in the match, nothing is
output unless the file name or line number are being
output.
If this option is given multiple times, multiple substrings are output for each match, in the order the options are given, and all on one line. For example, -o3 -o1 -o3 causes the substrings matched by capturing parentheses 3 and 1 and then 3 again to be output. By default, there is no separator (but see the next but one option).
−−om−capture
=numberSet the number of capturing parentheses that can be
accessed by −o
. The
default is 50.
−−om−separator
=textSpecify 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
=numberThis is an obsolete synonym for −−depth−limit
. See
−−match−limit
above
for details.
−s
, −−no−messages
Suppress error messages about non-existent or unreadable files. Such files are quietly skipped. However, the return code is still 2, even if matches were found in other files.
−t
, −−total−count
This option is useful when scanning more than one
file. If used on its own, −t
suppresses all output except
for a grand total number of matching lines (or
non-matching lines if −v
is used) in all the files. If
−t
is used with
−c
, a grand total is
output except when the previous output is just one
line. In other words, it is not output when just one
file's count is listed. If file names are being output,
the grand total is preceded by "TOTAL:". Otherwise, it
appears as just another number. The −t
option is ignored when used
with −L
(list files
without matches), because the grand total would always
be zero.
−u
, −−utf
Operate in UTF-8 mode. This option is available only
if PCRE2 has been compiled with UTF-8 support. All
patterns (including those for any −−exclude
and −−include
options) and all
lines that are scanned must be valid strings of UTF-8
characters. If an invalid UTF-8 string is encountered,
an error occurs.
−U
, −−utf−allow−invalid
As −−utf
,
but in addition subject lines may contain invalid UTF-8
code unit sequences. These can never form part of any
pattern match. Patterns themselves, however, must still
be valid UTF-8 strings. This facility allows valid
UTF-8 strings to be sought within arbitrary byte
sequences in executable or other binary files. For more
details about matching in non-valid UTF-8 strings, see
the pcre2unicode(3)
documentation.
−V
, −−version
Write the version numbers of pcre2grep and the PCRE2 library to the standard output and then exit. Anything else on the command line is ignored.
−v
, −−invert−match
Invert the sense of the match, so that lines which
do not match any of the patterns are the ones that are
found. When this option is set, options such as
−−only−matching
and
−−output
, which
specify parts of a match that are to be output, are
ignored.
−w
, −−word−regex
,
−−word−regexp
Force the patterns only to match "words". That is,
there must be a word boundary at the start and end of
each matched string. This is equivalent to having
"\b(?:" at the start of each pattern, and ")\b" at the
end. This option applies only to the patterns that are
matched against the contents of files; it does not
apply to patterns specified by any of the −−include
or −−exclude
options.
−x
, −−line−regex
,
−−line−regexp
Force the patterns to start matching only at the
beginnings of lines, and in addition, require them to
match entire lines. In multiline mode the match may be
more than one line. This is equivalent to having "^(?:"
at the start of each pattern and ")$" at the end. This
option applies only to the patterns that are matched
against the contents of files; it does not apply to
patterns specified by any of the −−include
or −−exclude
options.
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.
The −N
(−−newline
) option allows
pcre2grep to
scan files with newline conventions that differ from the
default. This option affects only the way scanned files are
processed. It does not affect the interpretation of files
specified by the −f
,
−−file−list
,
−−exclude−from
,
or −−include−from
options.
Any parts of the scanned input files that are written to the standard output are copied with whatever newline sequences they have in the input. However, if the final line of a file is output, and it does not end with a newline sequence, a newline sequence is added. If the newline setting is CR, LF, CRLF or NUL, that line ending is output; for the other settings (ANYCRLF or ANY) a single NL is used.
The newline setting does not affect the way in which pcre2grep writes newlines in informational messages to the standard output and error streams. Under Windows, the standard output is set to be binary, so that "\r\n" at the ends of output lines that are copied from the input is not converted to "\r\r\n" by the C I/O library. This means that any messages written to the standard output must end with "\r\n". For all other operating systems, and for all messages to the standard error stream, "\n" is used.
Many of the short and long forms of pcre2grep's options are the
same as in the GNU grep program. Any long
option of the form −−xxx−regexp
(GNU
terminology) is also available as −−xxx−regex
(PCRE2
terminology). However, the −−depth−limit
, −−file−list
, −−file−offsets
,
−−heap−limit
,
−−include−dir
,
−−line−offsets
,
−−locale
,
−−match−limit
,
−M
, −−multiline
, −N
, −−newline
, −−om−separator
,
−−output
,
−u
, −−utf
, −U
, and −−utf−allow−invalid
options are specific to pcre2grep, as is the use of
the −−only−matching
option with
a capturing parentheses number.
Although most of the common options work the same way, a
few are different in pcre2grep. For example, the
−−include
option's
argument is a glob for GNU grep, but a regular
expression for pcre2grep. If both the
−c
and −l
options are given, GNU grep lists
only file names, without counts, but pcre2grep gives the counts
as well.
There are four different ways in which an option with data can be specified. If a short form option is used, the data may follow immediately, or (with one exception) in the next command line item. For example:
-f/some/file -f /some/file
The exception is the −o
option, which may appear with or without data. Because of
this, if data is present, it must follow immediately in the
same item, for example -o3.
If a long form option is used, the data may appear in the same command line item, separated by an equals character, or (with two exceptions) it may appear in the next command line item. For example:
--file=/some/file --file /some/file
Note, however, that if you want to supply a file name beginning with ~ as data in a shell command, and have the shell expand ~ to a home directory, you must separate the file name from the option, because the shell does not treat ~ specially unless it is at the start of an item.
The exceptions to the above are the −−colour
(or −−color
) and −−only−matching
options,
for which the data is optional. If one of these options does
have data, it must be given in the first form, using an
equals character. Otherwise pcre2grep will assume that
it has no data.
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(3) documentation for details). Numbered callouts are ignored by pcre2grep; only callouts with string arguments are useful.
Starting the callout string with a pipe character
invokes an echoing facility that avoids calling an external
program or script. This facility is always available,
provided that callouts were not completely disabled when
pcre2grep was
built. The rest of the callout string is processed as a
zero-terminated string, which means it should not contain
any internal binary zeros. It is written to the output,
having first been passed through the same escape processing
as text from the −−output
(−O
) option (see above). However, $0
cannot be used to insert a matched substring because the
match is still in progress. Instead, the single character
'0' is inserted. Any syntax errors in the string (for
example, a dollar not followed by another character) causes
the callout to be ignored. No terminator is added to the
output string, so if you want a newline, you must include
it explicitly using the escape $n. For example:
pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' <some file>
Matching continues normally after the string is output. If you want to see only the callout output but not any output from an actual match, you should end the pattern with (*FAIL).
This facility can be independently disabled when
pcre2grep is
built. It is supported for Windows, where a call to
_spawnvp
() is used, for VMS,
where lib$spawn
() is used,
and for any Unix-like environment where fork
() and execv
() are available.
If the callout string does not start with a pipe (vertical bar) character, it is parsed into a list of substrings separated by pipe characters. The first substring must be an executable name, with the following substrings specifying arguments:
executable_name|arg1|arg2|...
Any substring (including the executable name) may
contain escape sequences started by a dollar character.
These are the same as for the −−output
(−O
) option documented above, except
that $0 cannot insert the matched string because the match
is still in progress. Instead, the character '0' is
inserted. If you need a literal dollar or pipe character in
any substring, use $$ or $| respectively. Here is an
example:
echo -e "abcde\n12345" | pcre2grep \ '(?x)(.)(..(.)) (?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
Output:
Arg1: [a] [bcd] [d] Arg2: |a| () abcde Arg1: [1] [234] [4] Arg2: |1| () 12345
The parameters for the system call that is used to run the program or script are zero-terminated strings. This means that binary zero characters in the callout argument will cause premature termination of their substrings, and therefore should not be present. Any syntax errors in the string (for example, a dollar not followed by another character) causes the callout to be ignored. If running the program fails for any reason (including the non-existence of the executable), a local matching failure occurs and the matcher backtracks in the normal way.
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.
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).
Last updated: 04 October 2020 Copyright (c) 1997-2020 University of Cambridge.
COPYRIGHT |
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This manual page is taken from the PCRE library, which is distributed under the BSD license. |