951 lines
46 KiB
HTML
951 lines
46 KiB
HTML
<html>
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<head>
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<title>pcre2grep specification</title>
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</head>
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<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
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<h1>pcre2grep man page</h1>
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<p>
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Return to the <a href="index.html">PCRE2 index page</a>.
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</p>
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<p>
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This page is part of the PCRE2 HTML documentation. It was generated
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automatically from the original man page. If there is any nonsense in it,
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please consult the man page, in case the conversion went wrong.
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<br>
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<ul>
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<li><a name="TOC1" href="#SEC1">SYNOPSIS</a>
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<li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
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<li><a name="TOC3" href="#SEC3">SUPPORT FOR COMPRESSED FILES</a>
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<li><a name="TOC4" href="#SEC4">BINARY FILES</a>
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<li><a name="TOC5" href="#SEC5">OPTIONS</a>
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<li><a name="TOC6" href="#SEC6">ENVIRONMENT VARIABLES</a>
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<li><a name="TOC7" href="#SEC7">NEWLINES</a>
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<li><a name="TOC8" href="#SEC8">OPTIONS COMPATIBILITY</a>
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<li><a name="TOC9" href="#SEC9">OPTIONS WITH DATA</a>
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<li><a name="TOC10" href="#SEC10">USING PCRE2'S CALLOUT FACILITY</a>
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<li><a name="TOC11" href="#SEC11">MATCHING ERRORS</a>
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<li><a name="TOC12" href="#SEC12">DIAGNOSTICS</a>
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<li><a name="TOC13" href="#SEC13">SEE ALSO</a>
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<li><a name="TOC14" href="#SEC14">AUTHOR</a>
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<li><a name="TOC15" href="#SEC15">REVISION</a>
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</ul>
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<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br>
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<P>
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<b>pcre2grep [options] [long options] [pattern] [path1 path2 ...]</b>
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</P>
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<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
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<P>
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<b>pcre2grep</b> searches files for character patterns, in the same way as other
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grep commands do, but it uses the PCRE2 regular expression library to support
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patterns that are compatible with the regular expressions of Perl 5. See
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<a href="pcre2syntax.html"><b>pcre2syntax</b>(3)</a>
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for a quick-reference summary of pattern syntax, or
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<a href="pcre2pattern.html"><b>pcre2pattern</b>(3)</a>
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for a full description of the syntax and semantics of the regular expressions
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that PCRE2 supports.
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</P>
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<P>
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Patterns, whether supplied on the command line or in a separate file, are given
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without delimiters. For example:
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<pre>
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pcre2grep Thursday /etc/motd
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</pre>
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If you attempt to use delimiters (for example, by surrounding a pattern with
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slashes, as is common in Perl scripts), they are interpreted as part of the
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pattern. Quotes can of course be used to delimit patterns on the command line
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because they are interpreted by the shell, and indeed quotes are required if a
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pattern contains white space or shell metacharacters.
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</P>
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<P>
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The first argument that follows any option settings is treated as the single
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pattern to be matched when neither <b>-e</b> nor <b>-f</b> is present.
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Conversely, when one or both of these options are used to specify patterns, all
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arguments are treated as path names. At least one of <b>-e</b>, <b>-f</b>, or an
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argument pattern must be provided.
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</P>
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<P>
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If no files are specified, <b>pcre2grep</b> reads the standard input. The
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standard input can also be referenced by a name consisting of a single hyphen.
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For example:
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<pre>
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pcre2grep some-pattern file1 - file3
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</pre>
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Input files are searched line by line. By default, each line that matches a
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pattern is copied to the standard output, and if there is more than one file,
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the file name is output at the start of each line, followed by a colon.
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However, there are options that can change how <b>pcre2grep</b> behaves. In
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particular, the <b>-M</b> option makes it possible to search for strings that
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span line boundaries. What defines a line boundary is controlled by the
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<b>-N</b> (<b>--newline</b>) option.
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</P>
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<P>
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The amount of memory used for buffering files that are being scanned is
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controlled by parameters that can be set by the <b>--buffer-size</b> and
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<b>--max-buffer-size</b> options. The first of these sets the size of buffer
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that is obtained at the start of processing. If an input file contains very
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long lines, a larger buffer may be needed; this is handled by automatically
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extending the buffer, up to the limit specified by <b>--max-buffer-size</b>. The
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default values for these parameters are specified when <b>pcre2grep</b> is
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built, with the default defaults being 20K and 1M respectively. An error occurs
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if a line is too long and the buffer can no longer be expanded.
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</P>
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<P>
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The block of memory that is actually used is three times the "buffer size", to
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allow for buffering "before" and "after" lines. If the buffer size is too
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small, fewer than requested "before" and "after" lines may be output.
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</P>
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<P>
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Patterns can be no longer than 8K or BUFSIZ bytes, whichever is the greater.
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BUFSIZ is defined in <b><stdio.h></b>. When there is more than one pattern
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(specified by the use of <b>-e</b> and/or <b>-f</b>), each pattern is applied to
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each line in the order in which they are defined, except that all the <b>-e</b>
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patterns are tried before the <b>-f</b> patterns.
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</P>
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<P>
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By default, as soon as one pattern matches a line, no further patterns are
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considered. However, if <b>--colour</b> (or <b>--color</b>) is used to colour the
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matching substrings, or if <b>--only-matching</b>, <b>--file-offsets</b>, or
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<b>--line-offsets</b> 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 found. If
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there are multiple patterns, they are all tried on the remainder of the line,
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but patterns that follow the one that matched are not tried on the earlier part
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of the line.
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</P>
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<P>
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This behaviour means that the order in which multiple patterns are specified
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can affect the output when one of the above options is used. This is no longer
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the same behaviour as GNU grep, which now manages to display earlier matches
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for later patterns (as long as there is no overlap).
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</P>
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<P>
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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 "(super)?(man)?", in
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which all components are optional. This pattern finds all occurrences of both
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"super" and "man"; the output differs from matching with "super|man" when only
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the matching substrings are being shown.
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</P>
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<P>
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If the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variable is set,
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<b>pcre2grep</b> uses the value to set a locale when calling the PCRE2 library.
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The <b>--locale</b> option can be used to override this.
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</P>
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<br><a name="SEC3" href="#TOC1">SUPPORT FOR COMPRESSED FILES</a><br>
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<P>
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It is possible to compile <b>pcre2grep</b> so that it uses <b>libz</b> or
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<b>libbz2</b> to read files whose names end in <b>.gz</b> or <b>.bz2</b>,
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respectively. You can find out whether your binary has support for one or both
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of these file types by running it with the <b>--help</b> option. If the
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appropriate support is not present, files are treated as plain text. The
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standard input is always so treated.
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</P>
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<br><a name="SEC4" href="#TOC1">BINARY FILES</a><br>
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<P>
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By default, a file that contains a binary zero byte within the first 1024 bytes
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is identified as a binary file, and is processed specially. (GNU grep
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identifies binary files in this manner.) However, if the newline type is
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specified as "nul", that is, the line terminator is a binary zero, the test for
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a binary file is not applied. See the <b>--binary-files</b> option for a means
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of changing the way binary files are handled.
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</P>
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<br><a name="SEC5" href="#TOC1">OPTIONS</a><br>
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<P>
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The order in which some of the options appear can affect the output. For
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example, both the <b>-h</b> and <b>-l</b> options affect the printing of file
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names. Whichever comes later in the command line will be the one that takes
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effect. Similarly, except where noted below, if an option is given twice, the
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later setting is used. Numerical values for options may be followed by K or M,
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to signify multiplication by 1024 or 1024*1024 respectively.
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</P>
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<P>
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<b>--</b>
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This terminates the list of options. It is useful if the next item on the
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command line starts with a hyphen but is not an option. This allows for the
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processing of patterns and file names that start with hyphens.
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</P>
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<P>
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<b>-A</b> <i>number</i>, <b>--after-context=</b><i>number</i>
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Output up to <i>number</i> lines of context after each matching line. Fewer
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lines are output if the next match or the end of the file is reached, or if the
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processing buffer size has been set too small. If file names and/or line
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numbers are being output, a hyphen separator is used instead of a colon for the
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context lines. A line containing "--" is output between each group of lines,
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unless they are in fact contiguous in the input file. The value of <i>number</i>
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is expected to be relatively small. When <b>-c</b> is used, <b>-A</b> is ignored.
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</P>
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<P>
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<b>-a</b>, <b>--text</b>
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Treat binary files as text. This is equivalent to
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<b>--binary-files</b>=<i>text</i>.
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</P>
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<P>
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<b>-B</b> <i>number</i>, <b>--before-context=</b><i>number</i>
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Output up to <i>number</i> lines of context before each matching line. Fewer
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lines are output if the previous match or the start of the file is within
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<i>number</i> lines, or if the processing buffer size has been set too small. If
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file names and/or line numbers are being output, a hyphen separator is used
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instead of a colon for the context lines. A line containing "--" is output
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between each group of lines, unless they are in fact contiguous in the input
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file. The value of <i>number</i> is expected to be relatively small. When
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<b>-c</b> is used, <b>-B</b> is ignored.
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</P>
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<P>
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<b>--binary-files=</b><i>word</i>
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Specify how binary files are to be processed. If the word is "binary" (the
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default), pattern matching is performed on binary files, but the only output is
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"Binary file <name> matches" when a match succeeds. If the word is "text",
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which is equivalent to the <b>-a</b> or <b>--text</b> option, binary files are
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processed in the same way as any other file. In this case, when a match
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succeeds, the output may be binary garbage, which can have nasty effects if
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sent to a terminal. If the word is "without-match", which is equivalent to the
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<b>-I</b> option, binary files are not processed at all; they are assumed not to
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be of interest and are skipped without causing any output or affecting the
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return code.
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</P>
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<P>
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<b>--buffer-size=</b><i>number</i>
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Set the parameter that controls how much memory is obtained at the start of
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processing for buffering files that are being scanned. See also
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<b>--max-buffer-size</b> below.
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</P>
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<P>
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<b>-C</b> <i>number</i>, <b>--context=</b><i>number</i>
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Output <i>number</i> lines of context both before and after each matching line.
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This is equivalent to setting both <b>-A</b> and <b>-B</b> to the same value.
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</P>
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<P>
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<b>-c</b>, <b>--count</b>
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Do not output lines from the files that are being scanned; instead output the
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number of lines that would have been shown, either because they matched, or, if
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<b>-v</b> is set, because they failed to match. By default, this count is
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exactly the same as the number of lines that would have been output, but if the
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<b>-M</b> (multiline) option is used (without <b>-v</b>), there may be more
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suppressed lines than the count (that is, the number of matches).
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<br>
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<br>
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If no lines are selected, the number zero is output. If several files are are
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being scanned, a count is output for each of them and the <b>-t</b> option can
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be used to cause a total to be output at the end. However, if the
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<b>--files-with-matches</b> option is also used, only those files whose counts
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are greater than zero are listed. When <b>-c</b> is used, the <b>-A</b>,
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<b>-B</b>, and <b>-C</b> options are ignored.
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</P>
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<P>
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<b>--colour</b>, <b>--color</b>
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If this option is given without any data, it is equivalent to "--colour=auto".
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If data is required, it must be given in the same shell item, separated by an
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equals sign.
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</P>
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<P>
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<b>--colour=</b><i>value</i>, <b>--color=</b><i>value</i>
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This option specifies under what circumstances the parts of a line that matched
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a pattern should be coloured in the output. By default, the output is not
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coloured. The value (which is optional, see above) may be "never", "always", or
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"auto". In the latter case, colouring happens only if the standard output is
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connected to a terminal. More resources are used when colouring is enabled,
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because <b>pcre2grep</b> has to search for all possible matches in a line, not
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just one, in order to colour them all.
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<br>
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<br>
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The colour that is used can be specified by setting one of the environment
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variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR, PCREGREP_COLOUR, or
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PCREGREP_COLOR, which are checked in that order. If none of these are set,
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<b>pcre2grep</b> looks for GREP_COLORS or GREP_COLOR (in that order). The value
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of the variable should be a string of two numbers, separated by a semicolon,
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except in the case of GREP_COLORS, which must start with "ms=" or "mt="
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followed by two semicolon-separated colours, terminated by the end of the
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string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is
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ignored, and GREP_COLOR is checked.
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<br>
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<br>
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If the string obtained from one of the above variables contains any characters
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other than semicolon or digits, the setting is ignored and the default colour
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is used. The string is copied directly into the control string for setting
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colour on a terminal, so it is your responsibility to ensure that the values
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make sense. If no relevant environment variable is set, the default is "1;31",
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which gives red.
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</P>
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<P>
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<b>-D</b> <i>action</i>, <b>--devices=</b><i>action</i>
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If an input path is not a regular file or a directory, "action" specifies how
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it is to be processed. Valid values are "read" (the default) or "skip"
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(silently skip the path).
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</P>
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<P>
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<b>-d</b> <i>action</i>, <b>--directories=</b><i>action</i>
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If an input path is a directory, "action" specifies how it is to be processed.
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Valid values are "read" (the default in non-Windows environments, for
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compatibility with GNU grep), "recurse" (equivalent to the <b>-r</b> option), or
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"skip" (silently skip the path, the default in Windows environments). In the
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"read" case, directories are read as if they were ordinary files. In some
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operating systems the effect of reading a directory like this is an immediate
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end-of-file; in others it may provoke an error.
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</P>
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<P>
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<b>--depth-limit</b>=<i>number</i>
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See <b>--match-limit</b> below.
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</P>
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<P>
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<b>-e</b> <i>pattern</i>, <b>--regex=</b><i>pattern</i>, <b>--regexp=</b><i>pattern</i>
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Specify a pattern to be matched. This option can be used multiple times in
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order to specify several patterns. It can also be used as a way of specifying a
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single pattern that starts with a hyphen. When <b>-e</b> is used, no argument
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pattern is taken 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 applied to each
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line in the order in which they are defined until one matches.
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<br>
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<br>
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If <b>-f</b> is used with <b>-e</b>, the command line patterns are matched first,
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followed by the patterns from the file(s), independent of the order in which
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these options are specified. Note that multiple use of <b>-e</b> is not the same
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as a single pattern with alternatives. For example, X|Y finds the first
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character in a line that is X or Y, whereas if the two patterns are given
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separately, with X first, <b>pcre2grep</b> finds X if it is present, even if it
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follows Y in the line. It finds Y only if there is no X in the line. This
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matters only if you are using <b>-o</b> or <b>--colo(u)r</b> to show the part(s)
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of the line that matched.
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</P>
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<P>
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<b>--exclude</b>=<i>pattern</i>
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Files (but not directories) whose names match the pattern are skipped without
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being processed. This applies to all files, whether listed on the command line,
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obtained from <b>--file-list</b>, or by scanning a directory. The pattern is a
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PCRE2 regular expression, and is matched against the final component of the
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file name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do
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not apply to this pattern. The option may be given any number of times in order
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to specify multiple patterns. If a file name matches both an <b>--include</b>
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and an <b>--exclude</b> pattern, it is excluded. There is no short form for this
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option.
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</P>
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<P>
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<b>--exclude-from=</b><i>filename</i>
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Treat each non-empty line of the file as the data for an <b>--exclude</b>
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option. What constitutes a newline when reading the file is the operating
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system's default. The <b>--newline</b> option has no effect on this option. This
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option may be given more than once in order to specify a number of files to
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read.
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</P>
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<P>
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<b>--exclude-dir</b>=<i>pattern</i>
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Directories whose names match the pattern are skipped without being processed,
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whatever the setting of the <b>--recursive</b> option. This applies to all
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directories, whether listed on the command line, obtained from
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<b>--file-list</b>, or by scanning a parent directory. The pattern is a PCRE2
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regular expression, and is matched against the final component of the directory
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name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not
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apply to this pattern. The option may be given any number of times in order to
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specify more than one pattern. If a directory matches both <b>--include-dir</b>
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and <b>--exclude-dir</b>, it is excluded. There is no short form for this
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option.
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</P>
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<P>
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<b>-F</b>, <b>--fixed-strings</b>
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Interpret each data-matching pattern as a list of fixed strings, separated by
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newlines, instead of as a regular expression. What constitutes a newline for
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this purpose is controlled by the <b>--newline</b> option. The <b>-w</b> (match
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as a word) and <b>-x</b> (match whole line) options can be used with <b>-F</b>.
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They apply to each of the fixed strings. A line is selected if any of the fixed
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strings are found in it (subject to <b>-w</b> or <b>-x</b>, if present). This
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option applies only to the patterns that are matched against the contents of
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files; it does not apply to patterns specified by any of the <b>--include</b> or
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<b>--exclude</b> options.
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</P>
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<P>
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<b>-f</b> <i>filename</i>, <b>--file=</b><i>filename</i>
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Read patterns from the file, one per line, and match them against each line of
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input. What constitutes a newline when reading the file is the operating
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system's default. The <b>--newline</b> option has no effect on this option.
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Trailing white space is removed from each line, and blank lines are ignored. An
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empty file contains no patterns and therefore matches nothing. See also the
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comments about multiple patterns versus a single pattern with alternatives in
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the description of <b>-e</b> above.
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<br>
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<br>
|
|
If this option is given more than once, all the specified files are read. A
|
|
data line is output if any of the patterns match it. A file name can be given
|
|
as "-" to refer to the standard input. When <b>-f</b> is used, patterns
|
|
specified on the command line using <b>-e</b> may also be present; they are
|
|
tested before the file's patterns. However, no other pattern is taken from the
|
|
command line; all arguments are treated as the names of paths to be searched.
|
|
</P>
|
|
<P>
|
|
<b>--file-list</b>=<i>filename</i>
|
|
Read a list of files and/or directories that are to be scanned from the given
|
|
file, one per line. Trailing white space is removed from each line, and blank
|
|
lines are ignored. These paths are processed before any that are listed on the
|
|
command line. The file name can be given as "-" to refer to the standard input.
|
|
If <b>--file</b> and <b>--file-list</b> are both specified as "-", patterns are
|
|
read first. This is useful only when the standard input is a terminal, from
|
|
which further lines (the list of files) can be read after an end-of-file
|
|
indication. If this option is given more than once, all the specified files are
|
|
read.
|
|
</P>
|
|
<P>
|
|
<b>--file-offsets</b>
|
|
Instead of showing lines or parts of lines that match, show each match as an
|
|
offset from the start of the file and a length, separated by a comma. In this
|
|
mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b>
|
|
options are ignored. If there is more than one match in a line, each of them is
|
|
shown separately. This option is mutually exclusive with <b>--output</b>,
|
|
<b>--line-offsets</b>, and <b>--only-matching</b>.
|
|
</P>
|
|
<P>
|
|
<b>-H</b>, <b>--with-filename</b>
|
|
Force the inclusion of the file name at the start of output lines when
|
|
searching a single file. By default, the file name is not shown in this case.
|
|
For matching lines, the file name is followed by a colon; for context lines, a
|
|
hyphen separator is used. If a line number is also being output, it follows the
|
|
file name. When the <b>-M</b> option causes a pattern to match more than one
|
|
line, only the first is preceded by the file name.
|
|
</P>
|
|
<P>
|
|
<b>-h</b>, <b>--no-filename</b>
|
|
Suppress the output file names when searching multiple files. By default,
|
|
file names are shown when multiple files are searched. For matching lines, the
|
|
file name is followed by a colon; for context lines, a hyphen separator is used.
|
|
If a line number is also being output, it follows the file name.
|
|
</P>
|
|
<P>
|
|
<b>--heap-limit</b>=<i>number</i>
|
|
See <b>--match-limit</b> below.
|
|
</P>
|
|
<P>
|
|
<b>--help</b>
|
|
Output a help message, giving brief details of the command options and file
|
|
type support, and then exit. Anything else on the command line is
|
|
ignored.
|
|
</P>
|
|
<P>
|
|
<b>-I</b>
|
|
Ignore binary files. This is equivalent to
|
|
<b>--binary-files</b>=<i>without-match</i>.
|
|
</P>
|
|
<P>
|
|
<b>-i</b>, <b>--ignore-case</b>
|
|
Ignore upper/lower case distinctions during comparisons.
|
|
</P>
|
|
<P>
|
|
<b>--include</b>=<i>pattern</i>
|
|
If any <b>--include</b> patterns are specified, the only files that are
|
|
processed are those that match one of the patterns (and do not match an
|
|
<b>--exclude</b> pattern). This option does not affect directories, but it
|
|
applies to all files, whether listed on the command line, obtained from
|
|
<b>--file-list</b>, or by scanning a directory. The pattern is a PCRE2 regular
|
|
expression, and is matched against the final component of the file name, not
|
|
the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not apply to
|
|
this pattern. The option may be given any number of times. If a file name
|
|
matches both an <b>--include</b> and an <b>--exclude</b> pattern, it is excluded.
|
|
There is no short form for this option.
|
|
</P>
|
|
<P>
|
|
<b>--include-from=</b><i>filename</i>
|
|
Treat each non-empty line of the file as the data for an <b>--include</b>
|
|
option. What constitutes a newline for this purpose is the operating system's
|
|
default. The <b>--newline</b> option has no effect on this option. This option
|
|
may be given any number of times; all the files are read.
|
|
</P>
|
|
<P>
|
|
<b>--include-dir</b>=<i>pattern</i>
|
|
If any <b>--include-dir</b> patterns are specified, the only directories that
|
|
are processed are those that match one of the patterns (and do not match an
|
|
<b>--exclude-dir</b> pattern). This applies to all directories, whether listed
|
|
on the command line, obtained from <b>--file-list</b>, or by scanning a parent
|
|
directory. The pattern is a PCRE2 regular expression, and is matched against
|
|
the final component of the directory name, not the entire path. The <b>-F</b>,
|
|
<b>-w</b>, and <b>-x</b> options do not apply to this pattern. The option may be
|
|
given any number of times. If a directory matches both <b>--include-dir</b> and
|
|
<b>--exclude-dir</b>, it is excluded. There is no short form for this option.
|
|
</P>
|
|
<P>
|
|
<b>-L</b>, <b>--files-without-match</b>
|
|
Instead of outputting lines from the files, just output the names of the files
|
|
that do not contain any lines that would have been output. Each file name is
|
|
output once, on a separate line.
|
|
</P>
|
|
<P>
|
|
<b>-l</b>, <b>--files-with-matches</b>
|
|
Instead of outputting lines from the files, just output the names of the files
|
|
containing lines that would have been output. Each file name is output
|
|
once, on a separate line. Searching normally stops as soon as a matching line
|
|
is found in a file. However, if the <b>-c</b> (count) option is also used,
|
|
matching continues in order to obtain the correct count, and those files that
|
|
have at least one match are listed along with their counts. Using this option
|
|
with <b>-c</b> is a way of suppressing the listing of files with no matches.
|
|
</P>
|
|
<P>
|
|
<b>--label</b>=<i>name</i>
|
|
This option supplies a name to be used for the standard input when file names
|
|
are being output. If not supplied, "(standard input)" is used. There is no
|
|
short form for this option.
|
|
</P>
|
|
<P>
|
|
<b>--line-buffered</b>
|
|
When this option is given, input is read and processed line by line, and the
|
|
output is flushed after each write. By default, input is read in large chunks,
|
|
unless <b>pcre2grep</b> can determine that it is reading from a terminal (which
|
|
is currently possible only in Unix-like environments). Output to terminal is
|
|
normally automatically flushed by the operating system. This option can be
|
|
useful when the input or output is attached to a pipe and you do not want
|
|
<b>pcre2grep</b> to buffer up large amounts of data. However, its use will
|
|
affect performance, and the <b>-M</b> (multiline) option ceases to work.
|
|
</P>
|
|
<P>
|
|
<b>--line-offsets</b>
|
|
Instead of showing lines or parts of lines that match, show each match as a
|
|
line number, the offset from the start of the line, and a length. The line
|
|
number is terminated by a colon (as usual; see the <b>-n</b> option), and the
|
|
offset and length are separated by a comma. In this mode, no context is shown.
|
|
That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b> options are ignored. If there is
|
|
more than one match in a line, each of them is shown separately. This option is
|
|
mutually exclusive with <b>--output</b>, <b>--file-offsets</b>, and
|
|
<b>--only-matching</b>.
|
|
</P>
|
|
<P>
|
|
<b>--locale</b>=<i>locale-name</i>
|
|
This option specifies a locale to be used for pattern matching. It overrides
|
|
the value in the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variables. If no
|
|
locale is specified, the PCRE2 library's default (usually the "C" locale) is
|
|
used. There is no short form for this option.
|
|
</P>
|
|
<P>
|
|
<b>--match-limit</b>=<i>number</i>
|
|
Processing some regular expression patterns may take a very long time to search
|
|
for all possible matching strings. Others may require a very large amount of
|
|
memory. There are three options that set resource limits for matching.
|
|
<br>
|
|
<br>
|
|
The <b>--match-limit</b> option provides a means of limiting computing resource
|
|
usage when processing patterns that are not going to match, but which have a
|
|
very large number of possibilities in their search trees. The classic example
|
|
is a pattern that uses nested unlimited repeats. Internally, PCRE2 has a
|
|
counter that is incremented each time around its main processing loop. If the
|
|
value set by <b>--match-limit</b> is reached, an error occurs.
|
|
<br>
|
|
<br>
|
|
The <b>--heap-limit</b> option specifies, as a number of kilobytes, the amount
|
|
of heap memory that may be used for matching. Heap memory is needed only if
|
|
matching the pattern requires a significant number of nested backtracking
|
|
points to be remembered. This parameter can be set to zero to forbid the use of
|
|
heap memory altogether.
|
|
<br>
|
|
<br>
|
|
The <b>--depth-limit</b> option limits the depth of nested backtracking points,
|
|
which indirectly limits the amount of memory that is used. The amount of memory
|
|
needed for each backtracking point depends on the number of capturing
|
|
parentheses in the pattern, so the amount of memory that is used before this
|
|
limit acts varies from pattern to pattern. This limit is of use only if it is
|
|
set smaller than <b>--match-limit</b>.
|
|
<br>
|
|
<br>
|
|
There are no short forms for these options. The default settings are specified
|
|
when the PCRE2 library is compiled, with the default defaults being very large
|
|
and so effectively unlimited.
|
|
</P>
|
|
<P>
|
|
\fB--max-buffer-size=<i>number</i>
|
|
This limits the expansion of the processing buffer, whose initial size can be
|
|
set by <b>--buffer-size</b>. The maximum buffer size is silently forced to be no
|
|
smaller than the starting buffer size.
|
|
</P>
|
|
<P>
|
|
<b>-M</b>, <b>--multiline</b>
|
|
Allow patterns to match more than one line. When this option is set, the PCRE2
|
|
library is called in "multiline" mode. This allows a matched string to extend
|
|
past the end of a line and continue on one or more subsequent lines. Patterns
|
|
used with <b>-M</b> may usefully contain literal newline characters and internal
|
|
occurrences of ^ and $ characters. The output for a successful match may
|
|
consist of more than one line. The first line is the line in which the match
|
|
started, and the last line is the line in which the match ended. If the matched
|
|
string ends with a newline sequence, the output ends at the end of that line.
|
|
If <b>-v</b> is set, none of the lines in a multi-line match are output. Once a
|
|
match has been handled, scanning restarts at the beginning of the line after
|
|
the one in which the match ended.
|
|
<br>
|
|
<br>
|
|
The newline sequence that separates multiple lines must be matched as part of
|
|
the pattern. For example, to find the phrase "regular expression" in a file
|
|
where "regular" might be at the end of a line and "expression" at the start of
|
|
the next line, you could use this command:
|
|
<pre>
|
|
pcre2grep -M 'regular\s+expression' <file>
|
|
</pre>
|
|
The \s escape sequence matches any white space character, including newlines,
|
|
and is followed by + so as to match trailing white space on the first line as
|
|
well as possibly handling a two-character newline sequence.
|
|
<br>
|
|
<br>
|
|
There is a limit to the number of lines that can be matched, imposed by the way
|
|
that <b>pcre2grep</b> buffers the input file as it scans it. With a sufficiently
|
|
large processing buffer, this should not be a problem, but the <b>-M</b> option
|
|
does not work when input is read line by line (see \fP--line-buffered\fP.)
|
|
</P>
|
|
<P>
|
|
<b>-N</b> <i>newline-type</i>, <b>--newline</b>=<i>newline-type</i>
|
|
The PCRE2 library supports five different conventions for indicating
|
|
the ends of lines. They are the single-character sequences CR (carriage return)
|
|
and LF (linefeed), the two-character sequence CRLF, an "anycrlf" convention,
|
|
which recognizes any of the preceding three types, and an "any" convention, in
|
|
which any Unicode line ending sequence is assumed to end a line. The Unicode
|
|
sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF
|
|
(form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and
|
|
PS (paragraph separator, U+2029).
|
|
<br>
|
|
<br>
|
|
When the PCRE2 library is built, a default line-ending sequence is specified.
|
|
This is normally the standard sequence for the operating system. Unless
|
|
otherwise specified by this option, <b>pcre2grep</b> uses the library's default.
|
|
The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This
|
|
makes it possible to use <b>pcre2grep</b> to scan files that have come from
|
|
other environments without having to modify their line endings. If the data
|
|
that is being scanned does not agree with the convention set by this option,
|
|
<b>pcre2grep</b> may behave in strange ways. Note that this option does not
|
|
apply to files specified by the <b>-f</b>, <b>--exclude-from</b>, or
|
|
<b>--include-from</b> options, which are expected to use the operating system's
|
|
standard newline sequence.
|
|
</P>
|
|
<P>
|
|
<b>-n</b>, <b>--line-number</b>
|
|
Precede each output line by its line number in the file, followed by a colon
|
|
for matching lines or a hyphen for context lines. If the file name is also
|
|
being output, it precedes the line number. When the <b>-M</b> option causes a
|
|
pattern to match more than one line, only the first is preceded by its line
|
|
number. This option is forced if <b>--line-offsets</b> is used.
|
|
</P>
|
|
<P>
|
|
<b>--no-jit</b>
|
|
If the PCRE2 library is built with support for just-in-time compiling (which
|
|
speeds up matching), <b>pcre2grep</b> automatically makes use of this, unless it
|
|
was explicitly disabled at build time. This option can be used to disable the
|
|
use of JIT at run time. It is provided for testing and working round problems.
|
|
It should never be needed in normal use.
|
|
</P>
|
|
<P>
|
|
<b>-O</b> <i>text</i>, <b>--output</b>=<i>text</i>
|
|
When there is a match, instead of outputting the whole line that matched,
|
|
output just the given text. This option is mutually exclusive with
|
|
<b>--only-matching</b>, <b>--file-offsets</b>, and <b>--line-offsets</b>. Escape
|
|
sequences starting with a dollar character may be used to insert the contents
|
|
of the matched part of the line and/or captured substrings into the text.
|
|
<br>
|
|
<br>
|
|
$<digits> or ${<digits>} is replaced by the captured
|
|
substring of the given decimal number; zero substitutes the whole match. If
|
|
the number is greater than the number of capturing substrings, or if the
|
|
capture is unset, the replacement is empty.
|
|
<br>
|
|
<br>
|
|
$a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by
|
|
newline; $r by carriage return; $t by tab; $v by vertical tab.
|
|
<br>
|
|
<br>
|
|
$o<digits> is replaced by the character represented by the given octal
|
|
number; up to three digits are processed.
|
|
<br>
|
|
<br>
|
|
$x<digits> is replaced by the character represented by the given hexadecimal
|
|
number; up to two digits are processed.
|
|
<br>
|
|
<br>
|
|
Any other character is substituted by itself. In particular, $$ is replaced by
|
|
a single dollar.
|
|
</P>
|
|
<P>
|
|
<b>-o</b>, <b>--only-matching</b>
|
|
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 <b>-A</b>, <b>-B</b>, and
|
|
<b>-C</b> options are ignored. If there is more than one match in a line, each
|
|
of them is shown separately, on a separate line of output. If <b>-o</b> is
|
|
combined with <b>-v</b> (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 <b>--output</b>,
|
|
<b>--file-offsets</b> and <b>--line-offsets</b>.
|
|
</P>
|
|
<P>
|
|
<b>-o</b><i>number</i>, <b>--only-matching</b>=<i>number</i>
|
|
Show only the part of the line that matched the capturing parentheses of the
|
|
given number. Up to 32 capturing parentheses are supported, and -o0 is
|
|
equivalent to <b>-o</b> without a number. Because these options can be given
|
|
without an argument (see above), if an argument is present, it must be given in
|
|
the same shell item, for example, -o3 or --only-matching=2. The comments given
|
|
for the non-argument case above also apply to this option. If the specified
|
|
capturing parentheses do not exist in the pattern, or were not set in the
|
|
match, nothing is output unless the file name or line number are being output.
|
|
<br>
|
|
<br>
|
|
If this option is given multiple times, multiple substrings are output for each
|
|
match, in the order the options are given, and all on one line. For example,
|
|
-o3 -o1 -o3 causes the substrings matched by capturing parentheses 3 and 1 and
|
|
then 3 again to be output. By default, there is no separator (but see the next
|
|
option).
|
|
</P>
|
|
<P>
|
|
<b>--om-separator</b>=<i>text</i>
|
|
Specify a separating string for multiple occurrences of <b>-o</b>. The default
|
|
is an empty string. Separating strings are never coloured.
|
|
</P>
|
|
<P>
|
|
<b>-q</b>, <b>--quiet</b>
|
|
Work quietly, that is, display nothing except error messages. The exit
|
|
status indicates whether or not any matches were found.
|
|
</P>
|
|
<P>
|
|
<b>-r</b>, <b>--recursive</b>
|
|
If any given path is a directory, recursively scan the files it contains,
|
|
taking note of any <b>--include</b> and <b>--exclude</b> settings. By default, a
|
|
directory is read as a normal file; in some operating systems this gives an
|
|
immediate end-of-file. This option is a shorthand for setting the <b>-d</b>
|
|
option to "recurse".
|
|
</P>
|
|
<P>
|
|
<b>--recursion-limit</b>=<i>number</i>
|
|
See <b>--match-limit</b> above.
|
|
</P>
|
|
<P>
|
|
<b>-s</b>, <b>--no-messages</b>
|
|
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.
|
|
</P>
|
|
<P>
|
|
<b>-t</b>, <b>--total-count</b>
|
|
This option is useful when scanning more than one file. If used on its own,
|
|
<b>-t</b> suppresses all output except for a grand total number of matching
|
|
lines (or non-matching lines if <b>-v</b> is used) in all the files. If <b>-t</b>
|
|
is used with <b>-c</b>, a grand total is output except when the previous output
|
|
is just one line. In other words, it is not output when just one file's count
|
|
is listed. If file names are being output, the grand total is preceded by
|
|
"TOTAL:". Otherwise, it appears as just another number. The <b>-t</b> option is
|
|
ignored when used with <b>-L</b> (list files without matches), because the grand
|
|
total would always be zero.
|
|
</P>
|
|
<P>
|
|
<b>-u</b>, <b>--utf-8</b>
|
|
Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled
|
|
with UTF-8 support. All patterns (including those for any <b>--exclude</b> and
|
|
<b>--include</b> options) and all subject lines that are scanned must be valid
|
|
strings of UTF-8 characters.
|
|
</P>
|
|
<P>
|
|
<b>-V</b>, <b>--version</b>
|
|
Write the version numbers of <b>pcre2grep</b> and the PCRE2 library to the
|
|
standard output and then exit. Anything else on the command line is
|
|
ignored.
|
|
</P>
|
|
<P>
|
|
<b>-v</b>, <b>--invert-match</b>
|
|
Invert the sense of the match, so that lines which do <i>not</i> match any of
|
|
the patterns are the ones that are found.
|
|
</P>
|
|
<P>
|
|
<b>-w</b>, <b>--word-regex</b>, <b>--word-regexp</b>
|
|
Force the patterns only to match "words". That is, there must be a word
|
|
boundary at the start and end of each matched string. This is equivalent to
|
|
having "\b(?:" at the start of each pattern, and ")\b" at the end. This
|
|
option applies only to the patterns that are matched against the contents of
|
|
files; it does not apply to patterns specified by any of the <b>--include</b> or
|
|
<b>--exclude</b> options.
|
|
</P>
|
|
<P>
|
|
<b>-x</b>, <b>--line-regex</b>, <b>--line-regexp</b>
|
|
Force the patterns to start matching only at the beginnings of lines, and in
|
|
addition, require them to match entire lines. In multiline mode the match may
|
|
be more than one line. This is equivalent to having "^(?:" at the start of each
|
|
pattern and ")$" at the end. This option applies only to the patterns that are
|
|
matched against the contents of files; it does not apply to patterns specified
|
|
by any of the <b>--include</b> or <b>--exclude</b> options.
|
|
</P>
|
|
<br><a name="SEC6" href="#TOC1">ENVIRONMENT VARIABLES</a><br>
|
|
<P>
|
|
The environment variables <b>LC_ALL</b> and <b>LC_CTYPE</b> are examined, in that
|
|
order, for a locale. The first one that is set is used. This can be overridden
|
|
by the <b>--locale</b> option. If no locale is set, the PCRE2 library's default
|
|
(usually the "C" locale) is used.
|
|
</P>
|
|
<br><a name="SEC7" href="#TOC1">NEWLINES</a><br>
|
|
<P>
|
|
The <b>-N</b> (<b>--newline</b>) option allows <b>pcre2grep</b> 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 whatever
|
|
newline sequences they have in the input. However, the setting of this option
|
|
does not affect the interpretation of files specified by the <b>-f</b>,
|
|
<b>--exclude-from</b>, or <b>--include-from</b> options, which are assumed to use
|
|
the operating system's standard newline sequence, nor does it affect the way in
|
|
which <b>pcre2grep</b> 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.
|
|
</P>
|
|
<br><a name="SEC8" href="#TOC1">OPTIONS COMPATIBILITY</a><br>
|
|
<P>
|
|
Many of the short and long forms of <b>pcre2grep</b>'s options are the same
|
|
as in the GNU <b>grep</b> program. Any long option of the form
|
|
<b>--xxx-regexp</b> (GNU terminology) is also available as <b>--xxx-regex</b>
|
|
(PCRE2 terminology). However, the <b>--depth-limit</b>, <b>--file-list</b>,
|
|
<b>--file-offsets</b>, <b>--heap-limit</b>, <b>--include-dir</b>,
|
|
<b>--line-offsets</b>, <b>--locale</b>, <b>--match-limit</b>, <b>-M</b>,
|
|
<b>--multiline</b>, <b>-N</b>, <b>--newline</b>, <b>--om-separator</b>,
|
|
<b>--output</b>, <b>-u</b>, and <b>--utf-8</b> options are specific to
|
|
<b>pcre2grep</b>, as is the use of the <b>--only-matching</b> option with a
|
|
capturing parentheses number.
|
|
</P>
|
|
<P>
|
|
Although most of the common options work the same way, a few are different in
|
|
<b>pcre2grep</b>. For example, the <b>--include</b> option's argument is a glob
|
|
for GNU <b>grep</b>, but a regular expression for <b>pcre2grep</b>. If both the
|
|
<b>-c</b> and <b>-l</b> options are given, GNU grep lists only file names,
|
|
without counts, but <b>pcre2grep</b> gives the counts as well.
|
|
</P>
|
|
<br><a name="SEC9" href="#TOC1">OPTIONS WITH DATA</a><br>
|
|
<P>
|
|
There are four different ways in which an option with data can be specified.
|
|
If a short form option is used, the data may follow immediately, or (with one
|
|
exception) in the next command line item. For example:
|
|
<pre>
|
|
-f/some/file
|
|
-f /some/file
|
|
</pre>
|
|
The exception is the <b>-o</b> 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.
|
|
</P>
|
|
<P>
|
|
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:
|
|
<pre>
|
|
--file=/some/file
|
|
--file /some/file
|
|
</pre>
|
|
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.
|
|
</P>
|
|
<P>
|
|
The exceptions to the above are the <b>--colour</b> (or <b>--color</b>) and
|
|
<b>--only-matching</b> 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 <b>pcre2grep</b> will assume that it has no data.
|
|
</P>
|
|
<br><a name="SEC10" href="#TOC1">USING PCRE2'S CALLOUT FACILITY</a><br>
|
|
<P>
|
|
<b>pcre2grep</b> has, by default, support for calling external programs or
|
|
scripts or echoing specific strings during matching by making use of PCRE2's
|
|
callout facility. However, this support can be disabled when <b>pcre2grep</b> is
|
|
built. You can find out whether your binary has support for callouts by running
|
|
it with the <b>--help</b> option. If the support is not enabled, all callouts in
|
|
patterns are ignored by <b>pcre2grep</b>.
|
|
</P>
|
|
<P>
|
|
A callout in a PCRE2 pattern is of the form (?C<arg>) where the argument is
|
|
either a number or a quoted string (see the
|
|
<a href="pcre2callout.html"><b>pcre2callout</b></a>
|
|
documentation for details). Numbered callouts are ignored by <b>pcre2grep</b>;
|
|
only callouts with string arguments are useful.
|
|
</P>
|
|
<br><b>
|
|
Calling external programs or scripts
|
|
</b><br>
|
|
<P>
|
|
If the callout string does not start with a pipe (vertical bar) character, it
|
|
is parsed into a list of substrings separated by pipe characters. The first
|
|
substring must be an executable name, with the following substrings specifying
|
|
arguments:
|
|
<pre>
|
|
executable_name|arg1|arg2|...
|
|
</pre>
|
|
Any substring (including the executable name) may contain escape sequences
|
|
started by a dollar character: $<digits> or ${<digits>} is replaced by the
|
|
captured substring of the given decimal number, which must be greater than
|
|
zero. If the number is greater than the number of capturing substrings, or if
|
|
the capture is unset, the replacement is empty.
|
|
</P>
|
|
<P>
|
|
Any other character is substituted by itself. In particular, $$ is replaced by
|
|
a single dollar and $| is replaced by a pipe character. Here is an example:
|
|
<pre>
|
|
echo -e "abcde\n12345" | pcre2grep \
|
|
'(?x)(.)(..(.))
|
|
(?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
|
|
|
|
Output:
|
|
|
|
Arg1: [a] [bcd] [d] Arg2: |a| ()
|
|
abcde
|
|
Arg1: [1] [234] [4] Arg2: |1| ()
|
|
12345
|
|
</pre>
|
|
The parameters for the <b>execv()</b> system call that is used to run the
|
|
program or script are zero-terminated strings. This means that binary zero
|
|
characters in the callout argument will cause premature termination of their
|
|
substrings, and therefore should not be present. Any syntax errors in the
|
|
string (for example, a dollar not followed by another character) cause the
|
|
callout to be ignored. If running the program fails for any reason (including
|
|
the non-existence of the executable), a local matching failure occurs and the
|
|
matcher backtracks in the normal way.
|
|
</P>
|
|
<br><b>
|
|
Echoing a specific string
|
|
</b><br>
|
|
<P>
|
|
If the callout string starts with a pipe (vertical bar) character, the rest of
|
|
the string is written to the output, having been passed through the same escape
|
|
processing as text from the --output option. This provides a simple echoing
|
|
facility that avoids calling an external program or script. No terminator is
|
|
added to the string, so if you want a newline, you must include it explicitly.
|
|
Matching continues normally after the string is output. If you want to see only
|
|
the callout output but not any output from an actual match, you should end the
|
|
relevant pattern with (*FAIL).
|
|
</P>
|
|
<br><a name="SEC11" href="#TOC1">MATCHING ERRORS</a><br>
|
|
<P>
|
|
It is possible to supply a regular expression that takes a very long time to
|
|
fail to match certain lines. Such patterns normally involve nested indefinite
|
|
repeats, for example: (a+)*\d when matched against a line of a's with no final
|
|
digit. The PCRE2 matching function has a resource limit that causes it to abort
|
|
in these circumstances. If this happens, <b>pcre2grep</b> outputs an error
|
|
message and the line that caused the problem to the standard error stream. If
|
|
there are more than 20 such errors, <b>pcre2grep</b> gives up.
|
|
</P>
|
|
<P>
|
|
The <b>--match-limit</b> option of <b>pcre2grep</b> can be used to set the
|
|
overall resource limit. There are also other limits that affect the amount of
|
|
memory used during matching; see the discussion of <b>--heap-limit</b> and
|
|
<b>--depth-limit</b> above.
|
|
</P>
|
|
<br><a name="SEC12" href="#TOC1">DIAGNOSTICS</a><br>
|
|
<P>
|
|
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
|
|
<b>-s</b> option to suppress error messages about inaccessible files does not
|
|
affect the return code.
|
|
</P>
|
|
<P>
|
|
When run under VMS, the return code is placed in the symbol PCRE2GREP_RC
|
|
because VMS does not distinguish between exit(0) and exit(1).
|
|
</P>
|
|
<br><a name="SEC13" href="#TOC1">SEE ALSO</a><br>
|
|
<P>
|
|
<b>pcre2pattern</b>(3), <b>pcre2syntax</b>(3), <b>pcre2callout</b>(3).
|
|
</P>
|
|
<br><a name="SEC14" href="#TOC1">AUTHOR</a><br>
|
|
<P>
|
|
Philip Hazel
|
|
<br>
|
|
University Computing Service
|
|
<br>
|
|
Cambridge, England.
|
|
<br>
|
|
</P>
|
|
<br><a name="SEC15" href="#TOC1">REVISION</a><br>
|
|
<P>
|
|
Last updated: 11 October 2017
|
|
<br>
|
|
Copyright © 1997-2017 University of Cambridge.
|
|
<br>
|
|
<p>
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
</p>
|