513 lines
27 KiB
Plaintext
513 lines
27 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 they 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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Patterns are limited to 8K or BUFSIZ characters, 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 (or fails to match when -v
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is used), no further patterns are considered. However, if --colour (or
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--color) is used to colour the matching substrings, or if --only-match-
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ing, --file-offsets, or --line-offsets is used to output only the part
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of the line that matched (either shown literally, or as an offset),
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scanning resumes immediately following the match, so that further
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matches on the same line can be found. If there are multiple patterns,
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they are all tried on the remainder of the line, but patterns that fol-
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low the one that matched are not tried on the earlier part of the line.
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This is the same behaviour as GNU grep, but it does mean that the order
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in which multiple patterns are specified can affect the output when one
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of the above options is used.
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Patterns that can match an empty string are accepted, but empty string
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matches are not recognized. An example is the pattern "(super)?(man)?",
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in which all components are optional. This pattern finds all occur-
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rences of both "super" and "man"; the output differs from matching with
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"super|man" when only the matching substrings are 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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OPTIONS
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-- This terminate 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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-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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-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; instead just output a count
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of the number of lines that would otherwise have been output.
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If several files are given, a count is output for each of
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them. In this mode, the -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),
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"recurse" (equivalent to the -r option), or "skip" (silently
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skip the path). In the default case, directories are read as
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if they were ordinary files. In some operating systems the
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effect of reading a directory like this is an immediate end-
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of-file.
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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 an overall maximum of 100 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 (or fails to match if -v is used). If -f is
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used with -e, the command line patterns are matched first,
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followed by the patterns from the file, independent of the
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order in which these options are specified. Note that multi-
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ple use of -e is not the same as a single pattern with alter-
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natives. For example, X|Y finds the first character in a line
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that is X or Y, whereas if the two patterns are given sepa-
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rately, pcregrep finds X if it is present, even if it follows
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Y in the line. It finds Y only if there is no X in the line.
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This really matters only if you are using -o to show the
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part(s) of the line that matched.
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--exclude=pattern
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When pcregrep is searching the files in a directory as a con-
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sequence of the -r (recursive search) option, any regular
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files whose names match the pattern are excluded. Subdirecto-
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ries are not excluded by this option; they are searched
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recursively, subject to the --exclude_dir and --include_dir
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options. The pattern is a PCRE regular expression, and is
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matched against the final component of the file name (not the
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entire path). If a file name matches both --include and
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--exclude, it is excluded. There is no short form for this
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option.
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--exclude_dir=pattern
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When pcregrep is searching the contents of a directory as a
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consequence of the -r (recursive search) option, any subdi-
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rectories whose names match the pattern are excluded. (Note
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that the --exclude option does not affect subdirectories.)
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The pattern is a PCRE regular expression, and is matched
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against the final component of the name (not the entire
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path). If a subdirectory name matches both --include_dir and
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--exclude_dir, it is excluded. There is no short form for
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this option.
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-F, --fixed-strings
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Interpret each pattern as a list of fixed strings, separated
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by newlines, instead of as a regular expression. The -w
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(match as a word) and -x (match whole line) options can be
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used with -F. They apply to each of the fixed strings. A line
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is selected if any of the fixed strings are found in it (sub-
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ject to -w or -x, if present).
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-f filename, --file=filename
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Read a number of patterns from the file, one per line, and
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match them against each line of input. A data line is output
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if any of the patterns match it. The filename can be given as
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"-" to refer to the standard input. When -f is used, patterns
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specified on the command line using -e may also be present;
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they are tested before the file's patterns. However, no other
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pattern is taken from the command line; all arguments are
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treated as file names. There is an overall maximum of 100
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patterns. Trailing white space is removed from each line, and
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blank lines are ignored. An empty file contains no patterns
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and therefore matches nothing. See also the comments about
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multiple patterns versus a single pattern with alternatives
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in the description of -e above.
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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.
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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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When pcregrep is searching the files in a directory as a con-
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sequence of the -r (recursive search) option, only those reg-
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ular files whose names match the pattern are included. Subdi-
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rectories are always included and searched recursively, sub-
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ject to the --include_dir and --exclude_dir options. The pat-
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tern is a PCRE regular expression, and is matched against the
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final component of the file name (not the entire path). If a
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file name matches both --include and --exclude, it is
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excluded. There is no short form for this option.
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--include_dir=pattern
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When pcregrep is searching the contents of a directory as a
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consequence of the -r (recursive search) option, only those
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subdirectories whose names match the pattern are included.
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(Note that the --include option does not affect subdirecto-
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ries.) The pattern is a PCRE regular expression, and is
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matched against the final component of the name (not the
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entire path). If a subdirectory name matches both
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--include_dir and --exclude_dir, it is excluded. There is no
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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 stops as soon as a matching line is found in a
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file.
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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-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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-M, --multiline
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Allow patterns to match more than one line. When this option
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is given, patterns may usefully contain literal newline char-
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acters and internal occurrences of ^ and $ characters. The
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output for any one match may consist of more than one line.
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When this option is set, the PCRE library is called in "mul-
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tiline" mode. There is a limit to the number of lines that
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can be matched, imposed by the way that pcregrep buffers the
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input file as it scans it. However, pcregrep ensures that at
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least 8K characters or the rest of the document (whichever is
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the shorter) are available for forward matching, and simi-
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larly the previous 8K characters (or all the previous charac-
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ters, if fewer than 8K) are guaranteed to be available for
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lookbehind assertions.
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-N newline-type, --newline=newline-type
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The PCRE library supports five different conventions for
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indicating the ends of lines. They are the single-character
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sequences CR (carriage return) and LF (linefeed), the two-
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character sequence CRLF, an "anycrlf" convention, which rec-
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ognizes any of the preceding three types, and an "any" con-
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vention, in which any Unicode line ending sequence is assumed
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to end a line. The Unicode sequences are the three just men-
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tioned, plus VT (vertical tab, U+000B), FF (formfeed,
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U+000C), NEL (next line, U+0085), LS (line separator,
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U+2028), and PS (paragraph separator, U+2029).
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When the PCRE library is built, a default line-ending
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sequence is specified. This is normally the standard
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sequence for the operating system. Unless otherwise specified
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by this option, pcregrep uses the library's default. The
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possible values for this option are CR, LF, CRLF, ANYCRLF, or
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ANY. This makes it possible to use pcregrep on files that
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have come from other environments without having to modify
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their line endings. If the data that is being scanned does
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not agree with the convention set by this option, pcregrep
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may behave in strange ways.
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-n, --line-number
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Precede each output line by its line number in the file, fol-
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lowed by a colon for matching lines or a hyphen for context
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lines. If the filename is also being output, it precedes the
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line number. This option is forced if --line-offsets is used.
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-o, --only-matching
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Show only the part of the line that matched a pattern. In
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this mode, no context is shown. That is, the -A, -B, and -C
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options are ignored. If there is more than one match in a
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line, each of them is shown separately. If -o is combined
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with -v (invert the sense of the match to find non-matching
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lines), no output is generated, but the return code is set
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appropriately. This option is mutually exclusive with --file-
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offsets and --line-offsets.
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-q, --quiet
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Work quietly, that is, display nothing except error messages.
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The exit status indicates whether or not any matches were
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found.
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-r, --recursive
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If any given path is a directory, recursively scan the files
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it contains, taking note of any --include and --exclude set-
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tings. By default, a directory is read as a normal file; in
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some operating systems this gives an immediate end-of-file.
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This option is a shorthand for setting the -d option to
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"recurse".
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-s, --no-messages
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Suppress error messages about non-existent or unreadable
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files. Such files are quietly skipped. However, the return
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code is still 2, even if matches were found in other files.
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-u, --utf-8
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Operate in UTF-8 mode. This option is available only if PCRE
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has been compiled with UTF-8 support. Both patterns and sub-
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ject lines must be valid strings of UTF-8 characters.
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-V, --version
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Write the version numbers of pcregrep and the PCRE library
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that is being used to the standard error stream.
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-v, --invert-match
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Invert the sense of the match, so that lines which do not
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match any of the patterns are the ones that are found.
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-w, --word-regex, --word-regexp
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Force the patterns to match only whole words. This is equiva-
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lent to having \b at the start and end of the pattern.
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-x, --line-regex, --line-regexp
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Force the patterns to be anchored (each must start matching
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at the beginning of a line) and in addition, require them to
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match entire lines. This is equivalent to having ^ and $
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characters at the start and end of each alternative branch in
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every pattern.
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ENVIRONMENT VARIABLES
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The environment variables LC_ALL and LC_CTYPE are examined, in that
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order, for a locale. The first one that is set is used. This can be
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overridden by the --locale option. If no locale is set, the PCRE
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library's default (usually the "C" locale) is used.
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NEWLINES
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The -N (--newline) option allows pcregrep to scan files with different
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newline conventions from the default. However, the setting of this
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option does not affect the way in which pcregrep writes information to
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the standard error and output streams. It uses the string "\n" in C
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printf() calls to indicate newlines, relying on the C I/O library to
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convert this to an appropriate sequence if the output is sent to a
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file.
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OPTIONS COMPATIBILITY
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The majority of short and long forms of pcregrep's options are the same
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as in the GNU grep program. Any long option of the form --xxx-regexp
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(GNU terminology) is also available as --xxx-regex (PCRE terminology).
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However, the --locale, -M, --multiline, -u, and --utf-8 options are
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specific to pcregrep.
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OPTIONS WITH DATA
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There are four different ways in which an option with data can be spec-
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ified. If a short form option is used, the data may follow immedi-
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ately, or in the next command line item. For example:
|
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|
|
-f/some/file
|
|
-f /some/file
|
|
|
|
If a long form option is used, the data may appear in the same command
|
|
line item, separated by an equals character, or (with one exception) it
|
|
may appear in the next command line item. For example:
|
|
|
|
--file=/some/file
|
|
--file /some/file
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|
|
|
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 exception to the above is the --colour (or --color) option, for
|
|
which the data is optional. If this option does have data, it must be
|
|
given in the first form, using an equals character. Otherwise it will
|
|
be assumed 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.
|
|
|
|
|
|
DIAGNOSTICS
|
|
|
|
Exit status is 0 if any matches were found, 1 if no matches were found,
|
|
and 2 for syntax errors and non-existent or inacessible files (even if
|
|
matches were found in other files) or too many matching errors. Using
|
|
the -s option to suppress error messages about inaccessble files does
|
|
not affect the return code.
|
|
|
|
|
|
SEE ALSO
|
|
|
|
pcrepattern(3), pcretest(1).
|
|
|
|
|
|
AUTHOR
|
|
|
|
Philip Hazel
|
|
University Computing Service
|
|
Cambridge CB2 3QH, England.
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|
|
|
|
|
REVISION
|
|
|
|
Last updated: 01 March 2009
|
|
Copyright (c) 1997-2009 University of Cambridge.
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