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PCRE2GREP(1) General Commands Manual PCRE2GREP(1)
NAME
pcre2grep - a grep with Perl-compatible regular expressions.
SYNOPSIS
pcre2grep [options] [long options] [pattern] [path1 path2 ...]
DESCRIPTION
pcre2grep searches files for character patterns, in the same way as
other grep commands do, but it uses the PCRE2 regular expression
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. Con-
versely, when one or both of these options are used to specify pat-
terns, all arguments are treated as path names. At least one of -e, -f,
or an argument pattern must be provided.
If no files are specified, pcre2grep reads the standard input. The
standard input can also be referenced by a name consisting of a single
hyphen. For example:
pcre2grep some-pattern file1 - file3
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 a parameter that can be set by the --buffer-size option.
The default value for this parameter is specified when pcre2grep is
built, with the default default being 20K. A block of memory three
times this size is used (to allow for buffering "before" and "after"
lines). An error occurs if a line overflows the buffer.
Patterns can be no longer than 8K 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 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.
SUPPORT FOR COMPRESSED FILES
It is possible to compile pcre2grep so that it uses libz or libbz2 to
read files whose names end in .gz or .bz2, respectively. You can find
out whether your 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, files are treated as plain text. The standard input is always
so treated.
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.
(GNU grep also identifies binary files in this manner.) See the
--binary-files option for a means of changing the way binary files are
handled.
OPTIONS
The order in which some of the options appear can affect the output.
For example, both the -h and -l options affect the printing of file
names. Whichever comes later in the command line will be the one that
takes effect. Similarly, except where noted below, if an option is
given twice, the later setting is used. Numerical values for options
may be followed by K or M, to signify multiplication by 1024 or
1024*1024 respectively.
-- This terminates the list of options. It is useful if the next
item on the command line starts with a hyphen but is not an
option. This allows for the processing of patterns and file
names that start with hyphens.
-A number, --after-context=number
Output number lines of context after each matching line. 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. However,
pcre2grep guarantees to have up to 8K of following text
available for context output.
-a, --text
Treat binary files as text. This is equivalent to --binary-
files=text.
-B number, --before-context=number
Output number lines of context before each matching line. 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. However,
pcre2grep guarantees to have up to 8K of preceding text
available for context output.
--binary-files=word
Specify how binary files are to be processed. If the word is
"binary" (the default), pattern matching is performed on
binary files, but the only output is "Binary file <name>
matches" when a match succeeds. If the word is "text", which
is equivalent to the -a or --text option, binary files are
processed in the same way as any other file. In this case,
when a match succeeds, the output may be binary garbage,
which can have nasty effects if sent to a terminal. If the
word is "without-match", which is equivalent to the -I
option, binary files are not processed at all; they are
assumed not to be of interest and are skipped without causing
any output or affecting the return code.
--buffer-size=number
Set the parameter that controls how much memory is used for
buffering files that are being scanned.
-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 matches (or non-matches if -v is
used) that would otherwise have caused lines to be shown. By
default, this count is the same as the number of suppressed
lines, but if the -M (multiline) option is used (without -v),
there may be more suppressed lines than the number of
matches.
If no lines are selected, the number zero is output. If sev-
eral files are are being scanned, a count is output for each
of them. However, if the --files-with-matches option is also
used, only those files whose counts are greater than zero are
listed. When -c is used, the -A, -B, and -C options are
ignored.
--colour, --color
If this option is given without any data, it is equivalent to
"--colour=auto". If data is required, it must be given in
the same shell item, separated by an equals sign.
--colour=value, --color=value
This option specifies under what circumstances the parts of a
line that matched a pattern should be coloured in the output.
By default, the output is not coloured. The value (which is
optional, see above) may be "never", "always", or "auto". In
the latter case, colouring happens only if the standard out-
put is connected to a terminal. More resources are used when
colouring is enabled, because pcre2grep has to search for all
possible matches in a line, not just one, in order to colour
them all.
The colour that is used can be specified by setting the envi-
ronment variable PCRE2GREP_COLOUR or PCRE2GREP_COLOR. The
value of this variable should be a string of two numbers,
separated by a semicolon. They are copied directly into the
control string for setting colour on a terminal, so it is
your responsibility to ensure that they make sense. If nei-
ther of the environment variables 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.
-e pattern, --regex=pattern, --regexp=pattern
Specify a pattern to be matched. This option can be used mul-
tiple times in order to specify several patterns. It can also
be used as a way of specifying a single pattern that starts
with a hyphen. When -e is used, no argument pattern is taken
from the command line; all arguments are treated as file
names. There is no limit to the number of patterns. They are
applied to each line in the order in which they are defined
until one matches.
If -f is used with -e, the command line patterns are matched
first, followed by the patterns from the file(s), independent
of the order in which these options are specified. Note that
multiple use of -e is not the same as a single pattern with
alternatives. For example, X|Y finds the first character in a
line that is X or Y, whereas if the two patterns are given
separately, with X first, pcre2grep finds X if it is present,
even if it follows Y in the line. It finds Y only if there is
no X in the line. This matters only if you are using -o or
--colo(u)r to show the part(s) of the line that matched.
--exclude=pattern
Files (but not directories) whose names match the pattern are
skipped without being processed. This applies to all files,
whether listed on the command line, obtained from --file-
list, or by scanning a directory. The pattern is a PCRE2 reg-
ular expression, and is matched against the final component
of the file name, not the entire path. The -F, -w, and -x
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 pat-
tern, it is excluded. There is no short form for this option.
--exclude-from=filename
Treat each non-empty line of the file as the data for an
--exclude option. What constitutes a newline when reading the
file is the operating system's default. The --newline option
has no effect on this option. This option may be given more
than once in order to specify a number of files to read.
--exclude-dir=pattern
Directories whose names match the pattern are skipped without
being processed, whatever the setting of the --recursive
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 direc-
tory 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, and match them
against each line of input. What constitutes a newline when
reading the file is the operating system's default. 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. 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=filename
Read a list of files and/or directories that are to be
scanned from the given file, one per line. 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 spec-
ified 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 --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.
-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.
--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 that match one of the patterns (and
do not match an --exclude pattern). This option does not
affect directories, but it applies to all files, whether
listed on the command line, obtained from --file-list, or by
scanning a directory. The pattern is a PCRE2 regular expres-
sion, and is matched against the final component of the file
name, not the entire path. The -F, -w, and -x options do not
apply to this pattern. The option may be given any number of
times. If a file name matches both an --include and an
--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 direc-
tories that are processed are those that 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 sepa-
rate line.
-l, --files-with-matches
Instead of outputting lines from the files, just output the
names of the files containing lines that would have been out-
put. Each file name is output once, on a separate line.
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 sup-
pressing the listing of files with no matches.
--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, 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 cur-
rently possible only in Unix-like environments). 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 perfor-
mance, and the -M (multiline) option ceases to work.
--line-offsets
Instead of showing lines or parts of lines that match, show
each match as a line number, the offset from the start of the
line, and a length. The line number is terminated by a colon
(as usual; see the -n option), and the offset and length are
separated by a comma. In this mode, no context is shown.
That is, the -A, -B, and -C options are ignored. If there is
more than one match in a line, each of them is shown sepa-
rately. This option is mutually exclusive with --file-offsets
and --only-matching.
--locale=locale-name
This option specifies a locale to be used for pattern match-
ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
ronment variables. If no locale is specified, the PCRE2
library's default (usually the "C" locale) is used. There is
no short form for this option.
--match-limit=number
Processing some regular expression patterns can require a
very large amount of memory, leading in some cases to a pro-
gram crash if not enough is available. Other patterns may
take a very long time to search for all possible matching
strings. The pcre2_match() function that is called by
pcre2grep to do the matching has two parameters that can
limit the resources that it uses.
The --match-limit option provides a means of limiting
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 uses a func-
tion called match() which it calls repeatedly (sometimes
recursively). The limit set by --match-limit is imposed on
the number of times this function is called during a match,
which has the effect of limiting the amount of backtracking
that can take place.
The --recursion-limit option is similar to --match-limit, but
instead of limiting the total number of times that match() is
called, it limits the depth of recursive calls, which in turn
limits the amount of memory that can be used. The recursion
depth is a smaller number than the total number of calls,
because not all calls to match() are recursive. This limit is
of use only if it is set smaller than --match-limit.
There are no short forms for these options. The default set-
tings are specified when the PCRE2 library is compiled, with
the default default being 10 million.
-M, --multiline
Allow patterns to match more than one line. When this option
is given, patterns may usefully contain literal newline char-
acters and internal occurrences of ^ and $ characters. The
output for a successful match may consist of more than one
line. The first is the line in which the match started, and
the last 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.
When this option is set, the PCRE2 library is called in "mul-
tiline" mode. However, pcre2grep still processes the input
line by line. The difference is that a matched string may
extend past the end of a line and continue on one or more
subsequent lines. The newline sequence 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. However, pcre2grep ensures that at least 8K
characters or the rest of the file (whichever is the shorter)
are available for forward matching, and similarly the previ-
ous 8K characters (or all the previous characters, if fewer
than 8K) are guaranteed to be available for lookbehind asser-
tions. The -M option does not work when input is read line by
line (see --line-buffered.)
-N newline-type, --newline=newline-type
The PCRE2 library supports five different conventions for
indicating the ends of lines. They are the single-character
sequences CR (carriage return) and LF (linefeed), the two-
character sequence CRLF, an "anycrlf" convention, which rec-
ognizes any of the preceding three types, and an "any" con-
vention, in which any Unicode line ending sequence is assumed
to end a line. The Unicode sequences are the three just men-
tioned, 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. The
possible values for this option are CR, LF, CRLF, ANYCRLF, or
ANY. This makes it possible to use pcre2grep to scan files
that have come from other environments without having to mod-
ify their line endings. If the data that is being scanned
does not agree with the convention set by this option,
pcre2grep may behave in strange ways. Note that this option
does not apply to files specified by the -f, --exclude-from,
or --include-from options, which are expected to use the
operating system's standard newline sequence.
-n, --line-number
Precede each output line by its line number in the file, fol-
lowed by a colon for matching lines or a hyphen for context
lines. If the file name is also being output, it precedes the
line number. When the -M option causes a pattern to match
more than one line, only the first is preceded by its line
number. This option is forced if --line-offsets is used.
--no-jit If the PCRE2 library is built with support for just-in-time
compiling (which speeds up matching), pcre2grep automatically
makes use of this, unless it was explicitly disabled at build
time. This option can be used to disable the use of JIT at
run time. It is provided for testing and working round prob-
lems. It should never be needed in normal use.
-o, --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.
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 --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 32 capturing parenthe-
ses are supported, and -o0 is equivalent to -o without a num-
ber. 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 case. 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 out-
put.
If this option is given multiple times, multiple substrings
are output, in the order the options are given. For example,
-o3 -o1 -o3 causes the substrings matched by capturing paren-
theses 3 and 1 and then 3 again to be output. By default,
there is no separator (but see the next option).
--om-separator=text
Specify a separating string for multiple occurrences of -o.
The default is an empty string. Separating strings are never
coloured.
-q, --quiet
Work quietly, that is, display nothing except error messages.
The exit status indicates whether or not any matches were
found.
-r, --recursive
If any given path is a directory, recursively scan the files
it contains, taking note of any --include and --exclude set-
tings. By default, a directory is read as a normal file; in
some operating systems this gives an immediate end-of-file.
This option is a shorthand for setting the -d option to
"recurse".
--recursion-limit=number
See --match-limit above.
-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.
-u, --utf-8
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 sub-
ject lines that are scanned must be valid strings of UTF-8
characters.
-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.
-w, --word-regex, --word-regexp
Force the patterns to match only whole words. This is equiva-
lent to having \b at the start and end of the pattern. This
option applies only to the patterns that are matched against
the contents of files; it does not apply to patterns speci-
fied by any of the --include or --exclude options.
-x, --line-regex, --line-regexp
Force the patterns to be anchored (each must start matching
at the beginning of a line) and in addition, require them to
match entire lines. This is equivalent to having ^ and $
characters at the start and end of each alternative top-level
branch in every pattern. This option applies only to the pat-
terns that are matched against the contents of files; it does
not apply to patterns specified by any of the --include or
--exclude options.
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 different
newline conventions from the default. Any parts of the input files that
are written to the standard output are copied identically, with what-
ever newline sequences they have in the input. However, the setting of
this option does not affect the interpretation of files specified by
the -f, --exclude-from, or --include-from options, which are assumed to
use the operating system's standard newline sequence, nor does it
affect the way in which pcre2grep writes informational messages to the
standard error and output streams. For these it uses the string "\n" to
indicate newlines, relying on the C I/O library to convert this to an
appropriate sequence.
OPTIONS COMPATIBILITY
Many of the short and long forms of pcre2grep's options are the same as
in the GNU grep program. Any long option of the form --xxx-regexp (GNU
terminology) is also available as --xxx-regex (PCRE2 terminology). How-
ever, the --file-list, --file-offsets, --include-dir, --line-offsets,
--locale, --match-limit, -M, --multiline, -N, --newline, --om-separa-
tor, --recursion-limit, -u, and --utf-8 options are specific to
pcre2grep, as is the use of the --only-matching option with a capturing
parentheses number.
Although most of the common options work the same way, a few are dif-
ferent in pcre2grep. For example, the --include option's argument is a
glob for GNU grep, but a regular expression for pcre2grep. If both the
-c and -l options are given, GNU grep lists only file names, without
counts, but pcre2grep gives the counts as well.
OPTIONS WITH DATA
There are four different ways in which an option with data can be spec-
ified. If a short form option is used, the data may follow immedi-
ately, or (with one exception) in the next command line item. For exam-
ple:
-f/some/file
-f /some/file
The exception is the -o option, which may appear with or without data.
Because of this, if data is present, it must follow immediately in the
same item, for example -o3.
If a long form option is used, the data may appear in the same command
line item, separated by an equals character, or (with two exceptions)
it may appear in the next command line item. For example:
--file=/some/file
--file /some/file
Note, however, that if you want to supply a file name beginning with ~
as data in a shell command, and have the shell expand ~ to a home
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.
CALLING EXTERNAL SCRIPTS
On non-Windows systems, pcre2grep has, by default, support for calling
external programs or scripts during matching by making use of PCRE2's
callout facility. However, this support can be disabled when pcre2grep
is built. You can find out whether your binary has support for call-
outs by running it with the --help option. If the support is not
enabled, all callouts in patterns are ignored by pcre2grep.
A callout in a PCRE2 pattern is of the form (?C<arg>) where the argu-
ment is either a number or a quoted string (see the pcre2callout docu-
mentation for details). Numbered callouts are ignored by pcre2grep.
String arguments are parsed as a list of substrings separated by pipe
(vertical bar) 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: $<digits> or ${<digits>} is
replaced by the captured substring of the given decimal number, which
must be greater than zero. If the number is greater than the number of
capturing substrings, or if the capture is unset, the replacement is
empty.
Any other character is substituted by itself. In particular, $$ is
replaced by a single dollar and $| is replaced by a pipe character.
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 execv() system call that is used to run the pro-
gram 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) cause 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 is a second option called --recursion-limit that
sets a limit on the amount of memory (usually stack) that is used (see
the discussion of these options above).
DIAGNOSTICS
Exit status is 0 if any matches were found, 1 if no matches were found,
and 2 for syntax errors, overlong lines, non-existent or inaccessible
files (even if matches were found in other files) or too many matching
errors. Using the -s option to suppress error messages about inaccessi-
ble files does not affect the return code.
SEE ALSO
pcre2pattern(3), pcre2syntax(3), pcre2callout(3).
AUTHOR
Philip Hazel
University Computing Service
Cambridge, England.
REVISION
Last updated: 06 April 2016
Copyright (c) 1997-2016 University of Cambridge.
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