741 lines
41 KiB
Plaintext
741 lines
41 KiB
Plaintext
PCREGREP(1) PCREGREP(1)
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NAME
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pcregrep - a grep with Perl-compatible regular expressions.
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SYNOPSIS
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pcregrep [options] [long options] [pattern] [path1 path2 ...]
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DESCRIPTION
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pcregrep searches files for character patterns, in the same way as
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other grep commands do, but it uses the PCRE regular expression library
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to support patterns that are compatible with the regular expressions of
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Perl 5. See pcrepattern(3) for a full description of syntax and seman-
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tics of the regular expressions that PCRE supports.
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Patterns, whether supplied on the command line or in a separate file,
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are given without delimiters. For example:
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pcregrep Thursday /etc/motd
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If you attempt to use delimiters (for example, by surrounding a pattern
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with slashes, as is common in Perl scripts), they are interpreted as
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part of the pattern. Quotes can of course be used to delimit patterns
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on the command line because they are interpreted by the shell, and
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indeed quotes are required if a pattern contains white space or shell
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metacharacters.
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The first argument that follows any option settings is treated as the
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single pattern to be matched when neither -e nor -f is present. Con-
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versely, when one or both of these options are used to specify pat-
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terns, all arguments are treated as path names. At least one of -e, -f,
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or an argument pattern must be provided.
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If no files are specified, pcregrep reads the standard input. The stan-
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dard input can also be referenced by a name consisting of a single
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hyphen. For example:
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pcregrep some-pattern /file1 - /file3
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By default, each line that matches a pattern is copied to the standard
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output, and if there is more than one file, the file name is output at
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the start of each line, followed by a colon. However, there are options
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that can change how pcregrep behaves. In particular, the -M option
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makes it possible to search for patterns that span line boundaries.
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What defines a line boundary is controlled by the -N (--newline)
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option.
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The amount of memory used for buffering files that are being scanned is
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controlled by a parameter that can be set by the --buffer-size option.
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The default value for this parameter is specified when pcregrep is
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built, with the default default being 20K. A block of memory three
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times this size is used (to allow for buffering "before" and "after"
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lines). An error occurs if a line overflows the buffer.
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Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the
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greater. BUFSIZ is defined in <stdio.h>. When there is more than one
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pattern (specified by the use of -e and/or -f), each pattern is applied
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to each line in the order in which they are defined, except that all
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the -e patterns are tried before the -f patterns.
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By default, as soon as one pattern matches a line, no further patterns
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are considered. However, if --colour (or --color) is used to colour the
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matching substrings, or if --only-matching, --file-offsets, or --line-
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offsets is used to output only the part of the line that matched
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(either shown literally, or as an offset), scanning resumes immediately
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following the match, so that further matches on the same line can be
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found. If there are multiple patterns, they are all tried on the
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remainder of the line, but patterns that follow the one that matched
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are not tried on the earlier part of the line.
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This behaviour means that the order in which multiple patterns are
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specified can affect the output when one of the above options is used.
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This is no longer the same behaviour as GNU grep, which now manages to
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display earlier matches for later patterns (as long as there is no
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overlap).
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Patterns that can match an empty string are accepted, but empty string
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matches are never recognized. An example is the pattern
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"(super)?(man)?", in which all components are optional. This pattern
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finds all occurrences of both "super" and "man"; the output differs
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from matching with "super|man" when only the matching substrings are
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being shown.
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If the LC_ALL or LC_CTYPE environment variable is set, pcregrep uses
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the value to set a locale when calling the PCRE library. The --locale
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option can be used to override this.
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SUPPORT FOR COMPRESSED FILES
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It is possible to compile pcregrep so that it uses libz or libbz2 to
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read files whose names end in .gz or .bz2, respectively. You can find
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out whether your binary has support for one or both of these file types
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by running it with the --help option. If the appropriate support is not
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present, files are treated as plain text. The standard input is always
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so treated.
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BINARY FILES
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By default, a file that contains a binary zero byte within the first
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1024 bytes is identified as a binary file, and is processed specially.
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(GNU grep also identifies binary files in this manner.) See the
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--binary-files option for a means of changing the way binary files are
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handled.
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OPTIONS
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The order in which some of the options appear can affect the output.
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For example, both the -h and -l options affect the printing of file
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names. Whichever comes later in the command line will be the one that
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takes effect. Similarly, except where noted below, if an option is
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given twice, the later setting is used. Numerical values for options
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may be followed by K or M, to signify multiplication by 1024 or
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1024*1024 respectively.
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-- This terminates the list of options. It is useful if the next
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item on the command line starts with a hyphen but is not an
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option. This allows for the processing of patterns and file-
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names that start with hyphens.
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-A number, --after-context=number
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Output number lines of context after each matching line. If
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filenames and/or line numbers are being output, a hyphen sep-
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arator is used instead of a colon for the context lines. A
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line containing "--" is output between each group of lines,
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unless they are in fact contiguous in the input file. The
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value of number is expected to be relatively small. However,
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pcregrep guarantees to have up to 8K of following text avail-
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able for context output.
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-a, --text
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Treat binary files as text. This is equivalent to --binary-
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files=text.
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-B number, --before-context=number
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Output number lines of context before each matching line. If
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filenames and/or line numbers are being output, a hyphen sep-
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arator is used instead of a colon for the context lines. A
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line containing "--" is output between each group of lines,
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unless they are in fact contiguous in the input file. The
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value of number is expected to be relatively small. However,
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pcregrep guarantees to have up to 8K of preceding text avail-
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able for context output.
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--binary-files=word
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Specify how binary files are to be processed. If the word is
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"binary" (the default), pattern matching is performed on
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binary files, but the only output is "Binary file <name>
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matches" when a match succeeds. If the word is "text", which
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is equivalent to the -a or --text option, binary files are
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processed in the same way as any other file. In this case,
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when a match succeeds, the output may be binary garbage,
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which can have nasty effects if sent to a terminal. If the
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word is "without-match", which is equivalent to the -I
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option, binary files are not processed at all; they are
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assumed not to be of interest.
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--buffer-size=number
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Set the parameter that controls how much memory is used for
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buffering files that are being scanned.
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-C number, --context=number
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Output number lines of context both before and after each
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matching line. This is equivalent to setting both -A and -B
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to the same value.
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-c, --count
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Do not output individual lines from the files that are being
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scanned; instead output the number of lines that would other-
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wise have been shown. If no lines are selected, the number
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zero is output. If several files are are being scanned, a
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count is output for each of them. However, if the --files-
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with-matches option is also used, only those files whose
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counts are greater than zero are listed. When -c is used, the
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-A, -B, and -C options are ignored.
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--colour, --color
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If this option is given without any data, it is equivalent to
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"--colour=auto". If data is required, it must be given in
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the same shell item, separated by an equals sign.
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--colour=value, --color=value
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This option specifies under what circumstances the parts of a
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line that matched a pattern should be coloured in the output.
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By default, the output is not coloured. The value (which is
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optional, see above) may be "never", "always", or "auto". In
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the latter case, colouring happens only if the standard out-
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put is connected to a terminal. More resources are used when
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colouring is enabled, because pcregrep has to search for all
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possible matches in a line, not just one, in order to colour
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them all.
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The colour that is used can be specified by setting the envi-
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ronment variable PCREGREP_COLOUR or PCREGREP_COLOR. The value
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of this variable should be a string of two numbers, separated
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by a semicolon. They are copied directly into the control
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string for setting colour on a terminal, so it is your
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responsibility to ensure that they make sense. If neither of
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the environment variables is set, the default is "1;31",
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which gives red.
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-D action, --devices=action
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If an input path is not a regular file or a directory,
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"action" specifies how it is to be processed. Valid values
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are "read" (the default) or "skip" (silently skip the path).
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-d action, --directories=action
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If an input path is a directory, "action" specifies how it is
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to be processed. Valid values are "read" (the default in
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non-Windows environments, for compatibility with GNU grep),
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"recurse" (equivalent to the -r option), or "skip" (silently
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skip the path, the default in Windows environments). In the
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"read" case, directories are read as if they were ordinary
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files. In some operating systems the effect of reading a
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directory like this is an immediate end-of-file; in others it
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may provoke an error.
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-e pattern, --regex=pattern, --regexp=pattern
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Specify a pattern to be matched. This option can be used mul-
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tiple times in order to specify several patterns. It can also
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be used as a way of specifying a single pattern that starts
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with a hyphen. When -e is used, no argument pattern is taken
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from the command line; all arguments are treated as file
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names. There is no limit to the number of patterns. They are
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applied to each line in the order in which they are defined
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until one matches.
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If -f is used with -e, the command line patterns are matched
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first, followed by the patterns from the file(s), independent
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of the order in which these options are specified. Note that
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multiple use of -e is not the same as a single pattern with
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alternatives. For example, X|Y finds the first character in a
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line that is X or Y, whereas if the two patterns are given
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separately, with X first, pcregrep finds X if it is present,
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even if it follows Y in the line. It finds Y only if there is
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no X in the line. This matters only if you are using -o or
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--colo(u)r to show the part(s) of the line that matched.
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--exclude=pattern
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Files (but not directories) whose names match the pattern are
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skipped without being processed. This applies to all files,
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whether listed on the command line, obtained from --file-
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list, or by scanning a directory. The pattern is a PCRE regu-
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lar expression, and is matched against the final component of
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the file name, not the entire path. The -F, -w, and -x
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options do not apply to this pattern. The option may be given
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any number of times in order to specify multiple patterns. If
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a file name matches both an --include and an --exclude pat-
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tern, it is excluded. There is no short form for this option.
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--exclude-from=filename
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Treat each non-empty line of the file as the data for an
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--exclude option. What constitutes a newline when reading the
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file is the operating system's default. The --newline option
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has no effect on this option. This option may be given more
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than once in order to specify a number of files to read.
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--exclude-dir=pattern
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Directories whose names match the pattern are skipped without
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being processed, whatever the setting of the --recursive
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option. This applies to all directories, whether listed on
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the command line, obtained from --file-list, or by scanning a
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parent directory. The pattern is a PCRE regular expression,
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and is matched against the final component of the directory
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name, not the entire path. The -F, -w, and -x options do not
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apply to this pattern. The option may be given any number of
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times in order to specify more than one pattern. If a direc-
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tory matches both --include-dir and --exclude-dir, it is
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excluded. There is no short form for this option.
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-F, --fixed-strings
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Interpret each data-matching pattern as a list of fixed
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strings, separated by newlines, instead of as a regular
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expression. What constitutes a newline for this purpose is
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controlled by the --newline option. The -w (match as a word)
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and -x (match whole line) options can be used with -F. They
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apply to each of the fixed strings. A line is selected if any
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of the fixed strings are found in it (subject to -w or -x, if
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present). This option applies only to the patterns that are
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matched against the contents of files; it does not apply to
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patterns specified by any of the --include or --exclude
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options.
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-f filename, --file=filename
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Read patterns from the file, one per line, and match them
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against each line of input. What constitutes a newline when
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reading the file is the operating system's default. The
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--newline option has no effect on this option. Trailing white
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space is removed from each line, and blank lines are ignored.
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An empty file contains no patterns and therefore matches
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nothing. See also the comments about multiple patterns versus
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a single pattern with alternatives in the description of -e
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above.
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If this option is given more than once, all the specified
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files are read. A data line is output if any of the patterns
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match it. A filename can be given as "-" to refer to the
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standard input. When -f is used, patterns specified on the
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command line using -e may also be present; they are tested
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before the file's patterns. However, no other pattern is
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taken from the command line; all arguments are treated as the
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names of paths to be searched.
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--file-list=filename
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Read a list of files and/or directories that are to be
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scanned from the given file, one per line. Trailing white
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space is removed from each line, and blank lines are ignored.
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These paths are processed before any that are listed on the
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command line. The filename can be given as "-" to refer to
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the standard input. If --file and --file-list are both spec-
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ified as "-", patterns are read first. This is useful only
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when the standard input is a terminal, from which further
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lines (the list of files) can be read after an end-of-file
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indication. If this option is given more than once, all the
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specified files are read.
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--file-offsets
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Instead of showing lines or parts of lines that match, show
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each match as an offset from the start of the file and a
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length, separated by a comma. In this mode, no context is
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shown. That is, the -A, -B, and -C options are ignored. If
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there is more than one match in a line, each of them is shown
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separately. This option is mutually exclusive with --line-
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offsets and --only-matching.
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-H, --with-filename
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Force the inclusion of the filename at the start of output
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lines when searching a single file. By default, the filename
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is not shown in this case. For matching lines, the filename
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is followed by a colon; for context lines, a hyphen separator
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is used. If a line number is also being output, it follows
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the file name.
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-h, --no-filename
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Suppress the output filenames when searching multiple files.
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By default, filenames are shown when multiple files are
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searched. For matching lines, the filename is followed by a
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colon; for context lines, a hyphen separator is used. If a
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line number is also being output, it follows the file name.
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--help Output a help message, giving brief details of the command
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options and file type support, and then exit. Anything else
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on the command line is ignored.
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-I Treat binary files as never matching. This is equivalent to
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--binary-files=without-match.
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-i, --ignore-case
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Ignore upper/lower case distinctions during comparisons.
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--include=pattern
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If any --include patterns are specified, the only files that
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are processed are those that match one of the patterns (and
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do not match an --exclude pattern). This option does not
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affect directories, but it applies to all files, whether
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listed on the command line, obtained from --file-list, or by
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scanning a directory. The pattern is a PCRE regular expres-
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sion, and is matched against the final component of the file
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name, not the entire path. The -F, -w, and -x options do not
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apply to this pattern. The option may be given any number of
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times. If a file name matches both an --include and an
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--exclude pattern, it is excluded. There is no short form
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for this option.
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--include-from=filename
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Treat each non-empty line of the file as the data for an
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--include option. What constitutes a newline for this purpose
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is the operating system's default. The --newline option has
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no effect on this option. This option may be given any number
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of times; all the files are read.
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--include-dir=pattern
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If any --include-dir patterns are specified, the only direc-
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tories that are processed are those that match one of the
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patterns (and do not match an --exclude-dir pattern). This
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applies to all directories, whether listed on the command
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line, obtained from --file-list, or by scanning a parent
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directory. The pattern is a PCRE regular expression, and is
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matched against the final component of the directory name,
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not the entire path. The -F, -w, and -x options do not apply
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to this pattern. The option may be given any number of times.
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If a directory matches both --include-dir and --exclude-dir,
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it is excluded. There is no short form for this option.
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-L, --files-without-match
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Instead of outputting lines from the files, just output the
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names of the files that do not contain any lines that would
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have been output. Each file name is output once, on a sepa-
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rate line.
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-l, --files-with-matches
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Instead of outputting lines from the files, just output the
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names of the files containing lines that would have been out-
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put. Each file name is output once, on a separate line.
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Searching normally stops as soon as a matching line is found
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in a file. However, if the -c (count) option is also used,
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matching continues in order to obtain the correct count, and
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those files that have at least one match are listed along
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with their counts. Using this option with -c is a way of sup-
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pressing the listing of files with no matches.
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--label=name
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This option supplies a name to be used for the standard input
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when file names are being output. If not supplied, "(standard
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input)" is used. There is no short form for this option.
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--line-buffered
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When this option is given, input is read and processed line
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by line, and the output is flushed after each write. By
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default, input is read in large chunks, unless pcregrep can
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determine that it is reading from a terminal (which is cur-
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rently possible only in Unix-like environments). Output to
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terminal is normally automatically flushed by the operating
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system. This option can be useful when the input or output is
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attached to a pipe and you do not want pcregrep to buffer up
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large amounts of data. However, its use will affect perfor-
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mance, and the -M (multiline) option ceases to work.
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--line-offsets
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Instead of showing lines or parts of lines that match, show
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each match as a line number, the offset from the start of the
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line, and a length. The line number is terminated by a colon
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(as usual; see the -n option), and the offset and length are
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separated by a comma. In this mode, no context is shown.
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That is, the -A, -B, and -C options are ignored. If there is
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more than one match in a line, each of them is shown sepa-
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rately. This option is mutually exclusive with --file-offsets
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and --only-matching.
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--locale=locale-name
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This option specifies a locale to be used for pattern match-
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ing. It overrides the value in the LC_ALL or LC_CTYPE envi-
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ronment variables. If no locale is specified, the PCRE
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library's default (usually the "C" locale) is used. There is
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no short form for this option.
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--match-limit=number
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Processing some regular expression patterns can require a
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very large amount of memory, leading in some cases to a pro-
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gram crash if not enough is available. Other patterns may
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take a very long time to search for all possible matching
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strings. The pcre_exec() function that is called by pcregrep
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to do the matching has two parameters that can limit the
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|
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, PCRE 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 PCRE 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 last of which is the one 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 PCRE library is called in "mul-
|
|
tiline" mode. There is a limit to the number of lines that
|
|
can be matched, imposed by the way that pcregrep buffers the
|
|
input file as it scans it. However, pcregrep ensures that at
|
|
least 8K characters or the rest of the document (whichever is
|
|
the shorter) are available for forward matching, and simi-
|
|
larly the previous 8K characters (or all the previous charac-
|
|
ters, if fewer than 8K) are guaranteed to be available for
|
|
lookbehind assertions. This option does not work when input
|
|
is read line by line (see --line-buffered.)
|
|
|
|
-N newline-type, --newline=newline-type
|
|
The PCRE 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 PCRE 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, pcregrep uses the library's default. The
|
|
possible values for this option are CR, LF, CRLF, ANYCRLF, or
|
|
ANY. This makes it possible to use pcregrep 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, pcre-
|
|
grep 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 operat-
|
|
ing 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 filename is also being output, it precedes the
|
|
line number. This option is forced if --line-offsets is used.
|
|
|
|
--no-jit If the PCRE library is built with support for just-in-time
|
|
compiling (which speeds up matching), pcregrep 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
|
|
printed.
|
|
|
|
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 PCRE
|
|
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 pcregrep and the PCRE library to
|
|
the standard output and then exit. Anything else on the com-
|
|
mand 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 branch in
|
|
every pattern. 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.
|
|
|
|
|
|
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 PCRE
|
|
library's default (usually the "C" locale) is used.
|
|
|
|
|
|
NEWLINES
|
|
|
|
The -N (--newline) option allows pcregrep 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 pcregrep 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 pcregrep'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 (PCRE 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 pcre-
|
|
grep, 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 pcregrep. For example, the --include option's argument is a
|
|
glob for GNU grep, but a regular expression for pcregrep. If both the
|
|
-c and -l options are given, GNU grep lists only file names, without
|
|
counts, but pcregrep gives the counts.
|
|
|
|
|
|
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 pcregrep will assume that it has no data.
|
|
|
|
|
|
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 PCRE matching function has a
|
|
resource limit that causes it to abort in these circumstances. If this
|
|
happens, pcregrep outputs an error message and the line that caused the
|
|
problem to the standard error stream. If there are more than 20 such
|
|
errors, pcregrep gives up.
|
|
|
|
The --match-limit option of pcregrep 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
|
|
|
|
pcrepattern(3), pcresyntax(3), pcretest(1).
|
|
|
|
|
|
AUTHOR
|
|
|
|
Philip Hazel
|
|
University Computing Service
|
|
Cambridge CB2 3QH, England.
|
|
|
|
|
|
REVISION
|
|
|
|
Last updated: 13 September 2012
|
|
Copyright (c) 1997-2012 University of Cambridge.
|