3 <title>pcre2grep specification</title>
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6 <h1>pcre2grep man page</h1>
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16 <li><a name="TOC1" href="#SEC1">SYNOPSIS</a>
17 <li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
18 <li><a name="TOC3" href="#SEC3">SUPPORT FOR COMPRESSED FILES</a>
19 <li><a name="TOC4" href="#SEC4">BINARY FILES</a>
20 <li><a name="TOC5" href="#SEC5">BINARY ZEROS IN PATTERNS</a>
21 <li><a name="TOC6" href="#SEC6">OPTIONS</a>
22 <li><a name="TOC7" href="#SEC7">ENVIRONMENT VARIABLES</a>
23 <li><a name="TOC8" href="#SEC8">NEWLINES</a>
24 <li><a name="TOC9" href="#SEC9">OPTIONS COMPATIBILITY</a>
25 <li><a name="TOC10" href="#SEC10">OPTIONS WITH DATA</a>
26 <li><a name="TOC11" href="#SEC11">USING PCRE2'S CALLOUT FACILITY</a>
27 <li><a name="TOC12" href="#SEC12">MATCHING ERRORS</a>
28 <li><a name="TOC13" href="#SEC13">DIAGNOSTICS</a>
29 <li><a name="TOC14" href="#SEC14">SEE ALSO</a>
30 <li><a name="TOC15" href="#SEC15">AUTHOR</a>
31 <li><a name="TOC16" href="#SEC16">REVISION</a>
33 <br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br>
35 <b>pcre2grep [options] [long options] [pattern] [path1 path2 ...]</b>
37 <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
39 <b>pcre2grep</b> searches files for character patterns, in the same way as other
40 grep commands do, but it uses the PCRE2 regular expression library to support
41 patterns that are compatible with the regular expressions of Perl 5. See
42 <a href="pcre2syntax.html"><b>pcre2syntax</b>(3)</a>
43 for a quick-reference summary of pattern syntax, or
44 <a href="pcre2pattern.html"><b>pcre2pattern</b>(3)</a>
45 for a full description of the syntax and semantics of the regular expressions
49 Patterns, whether supplied on the command line or in a separate file, are given
50 without delimiters. For example:
52 pcre2grep Thursday /etc/motd
54 If you attempt to use delimiters (for example, by surrounding a pattern with
55 slashes, as is common in Perl scripts), they are interpreted as part of the
56 pattern. Quotes can of course be used to delimit patterns on the command line
57 because they are interpreted by the shell, and indeed quotes are required if a
58 pattern contains white space or shell metacharacters.
61 The first argument that follows any option settings is treated as the single
62 pattern to be matched when neither <b>-e</b> nor <b>-f</b> is present.
63 Conversely, when one or both of these options are used to specify patterns, all
64 arguments are treated as path names. At least one of <b>-e</b>, <b>-f</b>, or an
65 argument pattern must be provided.
68 If no files are specified, <b>pcre2grep</b> reads the standard input. The
69 standard input can also be referenced by a name consisting of a single hyphen.
72 pcre2grep some-pattern file1 - file3
74 Input files are searched line by line. By default, each line that matches a
75 pattern is copied to the standard output, and if there is more than one file,
76 the file name is output at the start of each line, followed by a colon.
77 However, there are options that can change how <b>pcre2grep</b> behaves. In
78 particular, the <b>-M</b> option makes it possible to search for strings that
79 span line boundaries. What defines a line boundary is controlled by the
80 <b>-N</b> (<b>--newline</b>) option.
83 The amount of memory used for buffering files that are being scanned is
84 controlled by parameters that can be set by the <b>--buffer-size</b> and
85 <b>--max-buffer-size</b> options. The first of these sets the size of buffer
86 that is obtained at the start of processing. If an input file contains very
87 long lines, a larger buffer may be needed; this is handled by automatically
88 extending the buffer, up to the limit specified by <b>--max-buffer-size</b>. The
89 default values for these parameters can be set when <b>pcre2grep</b> is
90 built; if nothing is specified, the defaults are set to 20KiB and 1MiB
91 respectively. An error occurs if a line is too long and the buffer can no
95 The block of memory that is actually used is three times the "buffer size", to
96 allow for buffering "before" and "after" lines. If the buffer size is too
97 small, fewer than requested "before" and "after" lines may be output.
100 Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater.
101 BUFSIZ is defined in <b><stdio.h></b>. When there is more than one pattern
102 (specified by the use of <b>-e</b> and/or <b>-f</b>), each pattern is applied to
103 each line in the order in which they are defined, except that all the <b>-e</b>
104 patterns are tried before the <b>-f</b> patterns.
107 By default, as soon as one pattern matches a line, no further patterns are
108 considered. However, if <b>--colour</b> (or <b>--color</b>) is used to colour the
109 matching substrings, or if <b>--only-matching</b>, <b>--file-offsets</b>, or
110 <b>--line-offsets</b> is used to output only the part of the line that matched
111 (either shown literally, or as an offset), scanning resumes immediately
112 following the match, so that further matches on the same line can be found. If
113 there are multiple patterns, they are all tried on the remainder of the line,
114 but patterns that follow the one that matched are not tried on the earlier part
118 This behaviour means that the order in which multiple patterns are specified
119 can affect the output when one of the above options is used. This is no longer
120 the same behaviour as GNU grep, which now manages to display earlier matches
121 for later patterns (as long as there is no overlap).
124 Patterns that can match an empty string are accepted, but empty string
125 matches are never recognized. An example is the pattern "(super)?(man)?", in
126 which all components are optional. This pattern finds all occurrences of both
127 "super" and "man"; the output differs from matching with "super|man" when only
128 the matching substrings are being shown.
131 If the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variable is set,
132 <b>pcre2grep</b> uses the value to set a locale when calling the PCRE2 library.
133 The <b>--locale</b> option can be used to override this.
135 <br><a name="SEC3" href="#TOC1">SUPPORT FOR COMPRESSED FILES</a><br>
137 It is possible to compile <b>pcre2grep</b> so that it uses <b>libz</b> or
138 <b>libbz2</b> to read compressed files whose names end in <b>.gz</b> or
139 <b>.bz2</b>, respectively. You can find out whether your <b>pcre2grep</b> binary
140 has support for one or both of these file types by running it with the
141 <b>--help</b> option. If the appropriate support is not present, all files are
142 treated as plain text. The standard input is always so treated. When input is
143 from a compressed .gz or .bz2 file, the <b>--line-buffered</b> option is
146 <br><a name="SEC4" href="#TOC1">BINARY FILES</a><br>
148 By default, a file that contains a binary zero byte within the first 1024 bytes
149 is identified as a binary file, and is processed specially. (GNU grep
150 identifies binary files in this manner.) However, if the newline type is
151 specified as "nul", that is, the line terminator is a binary zero, the test for
152 a binary file is not applied. See the <b>--binary-files</b> option for a means
153 of changing the way binary files are handled.
155 <br><a name="SEC5" href="#TOC1">BINARY ZEROS IN PATTERNS</a><br>
157 Patterns passed from the command line are strings that are terminated by a
158 binary zero, so cannot contain internal zeros. However, patterns that are read
159 from a file via the <b>-f</b> option may contain binary zeros.
161 <br><a name="SEC6" href="#TOC1">OPTIONS</a><br>
163 The order in which some of the options appear can affect the output. For
164 example, both the <b>-H</b> and <b>-l</b> options affect the printing of file
165 names. Whichever comes later in the command line will be the one that takes
166 effect. Similarly, except where noted below, if an option is given twice, the
167 later setting is used. Numerical values for options may be followed by K or M,
168 to signify multiplication by 1024 or 1024*1024 respectively.
172 This terminates the list of options. It is useful if the next item on the
173 command line starts with a hyphen but is not an option. This allows for the
174 processing of patterns and file names that start with hyphens.
177 <b>-A</b> <i>number</i>, <b>--after-context=</b><i>number</i>
178 Output up to <i>number</i> lines of context after each matching line. Fewer
179 lines are output if the next match or the end of the file is reached, or if the
180 processing buffer size has been set too small. If file names and/or line
181 numbers are being output, a hyphen separator is used instead of a colon for the
182 context lines. A line containing "--" is output between each group of lines,
183 unless they are in fact contiguous in the input file. The value of <i>number</i>
184 is expected to be relatively small. When <b>-c</b> is used, <b>-A</b> is ignored.
187 <b>-a</b>, <b>--text</b>
188 Treat binary files as text. This is equivalent to
189 <b>--binary-files</b>=<i>text</i>.
192 <b>-B</b> <i>number</i>, <b>--before-context=</b><i>number</i>
193 Output up to <i>number</i> lines of context before each matching line. Fewer
194 lines are output if the previous match or the start of the file is within
195 <i>number</i> lines, or if the processing buffer size has been set too small. If
196 file names and/or line numbers are being output, a hyphen separator is used
197 instead of a colon for the context lines. A line containing "--" is output
198 between each group of lines, unless they are in fact contiguous in the input
199 file. The value of <i>number</i> is expected to be relatively small. When
200 <b>-c</b> is used, <b>-B</b> is ignored.
203 <b>--binary-files=</b><i>word</i>
204 Specify how binary files are to be processed. If the word is "binary" (the
205 default), pattern matching is performed on binary files, but the only output is
206 "Binary file <name> matches" when a match succeeds. If the word is "text",
207 which is equivalent to the <b>-a</b> or <b>--text</b> option, binary files are
208 processed in the same way as any other file. In this case, when a match
209 succeeds, the output may be binary garbage, which can have nasty effects if
210 sent to a terminal. If the word is "without-match", which is equivalent to the
211 <b>-I</b> option, binary files are not processed at all; they are assumed not to
212 be of interest and are skipped without causing any output or affecting the
216 <b>--buffer-size=</b><i>number</i>
217 Set the parameter that controls how much memory is obtained at the start of
218 processing for buffering files that are being scanned. See also
219 <b>--max-buffer-size</b> below.
222 <b>-C</b> <i>number</i>, <b>--context=</b><i>number</i>
223 Output <i>number</i> lines of context both before and after each matching line.
224 This is equivalent to setting both <b>-A</b> and <b>-B</b> to the same value.
227 <b>-c</b>, <b>--count</b>
228 Do not output lines from the files that are being scanned; instead output the
229 number of lines that would have been shown, either because they matched, or, if
230 <b>-v</b> is set, because they failed to match. By default, this count is
231 exactly the same as the number of lines that would have been output, but if the
232 <b>-M</b> (multiline) option is used (without <b>-v</b>), there may be more
233 suppressed lines than the count (that is, the number of matches).
236 If no lines are selected, the number zero is output. If several files are are
237 being scanned, a count is output for each of them and the <b>-t</b> option can
238 be used to cause a total to be output at the end. However, if the
239 <b>--files-with-matches</b> option is also used, only those files whose counts
240 are greater than zero are listed. When <b>-c</b> is used, the <b>-A</b>,
241 <b>-B</b>, and <b>-C</b> options are ignored.
244 <b>--colour</b>, <b>--color</b>
245 If this option is given without any data, it is equivalent to "--colour=auto".
246 If data is required, it must be given in the same shell item, separated by an
250 <b>--colour=</b><i>value</i>, <b>--color=</b><i>value</i>
251 This option specifies under what circumstances the parts of a line that matched
252 a pattern should be coloured in the output. By default, the output is not
253 coloured. The value (which is optional, see above) may be "never", "always", or
254 "auto". In the latter case, colouring happens only if the standard output is
255 connected to a terminal. More resources are used when colouring is enabled,
256 because <b>pcre2grep</b> has to search for all possible matches in a line, not
257 just one, in order to colour them all.
260 The colour that is used can be specified by setting one of the environment
261 variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR, PCREGREP_COLOUR, or
262 PCREGREP_COLOR, which are checked in that order. If none of these are set,
263 <b>pcre2grep</b> looks for GREP_COLORS or GREP_COLOR (in that order). The value
264 of the variable should be a string of two numbers, separated by a semicolon,
265 except in the case of GREP_COLORS, which must start with "ms=" or "mt="
266 followed by two semicolon-separated colours, terminated by the end of the
267 string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is
268 ignored, and GREP_COLOR is checked.
271 If the string obtained from one of the above variables contains any characters
272 other than semicolon or digits, the setting is ignored and the default colour
273 is used. The string is copied directly into the control string for setting
274 colour on a terminal, so it is your responsibility to ensure that the values
275 make sense. If no relevant environment variable is set, the default is "1;31",
279 <b>-D</b> <i>action</i>, <b>--devices=</b><i>action</i>
280 If an input path is not a regular file or a directory, "action" specifies how
281 it is to be processed. Valid values are "read" (the default) or "skip"
282 (silently skip the path).
285 <b>-d</b> <i>action</i>, <b>--directories=</b><i>action</i>
286 If an input path is a directory, "action" specifies how it is to be processed.
287 Valid values are "read" (the default in non-Windows environments, for
288 compatibility with GNU grep), "recurse" (equivalent to the <b>-r</b> option), or
289 "skip" (silently skip the path, the default in Windows environments). In the
290 "read" case, directories are read as if they were ordinary files. In some
291 operating systems the effect of reading a directory like this is an immediate
292 end-of-file; in others it may provoke an error.
295 <b>--depth-limit</b>=<i>number</i>
296 See <b>--match-limit</b> below.
299 <b>-e</b> <i>pattern</i>, <b>--regex=</b><i>pattern</i>, <b>--regexp=</b><i>pattern</i>
300 Specify a pattern to be matched. This option can be used multiple times in
301 order to specify several patterns. It can also be used as a way of specifying a
302 single pattern that starts with a hyphen. When <b>-e</b> is used, no argument
303 pattern is taken from the command line; all arguments are treated as file
304 names. There is no limit to the number of patterns. They are applied to each
305 line in the order in which they are defined until one matches.
308 If <b>-f</b> is used with <b>-e</b>, the command line patterns are matched first,
309 followed by the patterns from the file(s), independent of the order in which
310 these options are specified. Note that multiple use of <b>-e</b> is not the same
311 as a single pattern with alternatives. For example, X|Y finds the first
312 character in a line that is X or Y, whereas if the two patterns are given
313 separately, with X first, <b>pcre2grep</b> finds X if it is present, even if it
314 follows Y in the line. It finds Y only if there is no X in the line. This
315 matters only if you are using <b>-o</b> or <b>--colo(u)r</b> to show the part(s)
316 of the line that matched.
319 <b>--exclude</b>=<i>pattern</i>
320 Files (but not directories) whose names match the pattern are skipped without
321 being processed. This applies to all files, whether listed on the command line,
322 obtained from <b>--file-list</b>, or by scanning a directory. The pattern is a
323 PCRE2 regular expression, and is matched against the final component of the
324 file name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do
325 not apply to this pattern. The option may be given any number of times in order
326 to specify multiple patterns. If a file name matches both an <b>--include</b>
327 and an <b>--exclude</b> pattern, it is excluded. There is no short form for this
331 <b>--exclude-from=</b><i>filename</i>
332 Treat each non-empty line of the file as the data for an <b>--exclude</b>
333 option. What constitutes a newline when reading the file is the operating
334 system's default. The <b>--newline</b> option has no effect on this option. This
335 option may be given more than once in order to specify a number of files to
339 <b>--exclude-dir</b>=<i>pattern</i>
340 Directories whose names match the pattern are skipped without being processed,
341 whatever the setting of the <b>--recursive</b> option. This applies to all
342 directories, whether listed on the command line, obtained from
343 <b>--file-list</b>, or by scanning a parent directory. The pattern is a PCRE2
344 regular expression, and is matched against the final component of the directory
345 name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not
346 apply to this pattern. The option may be given any number of times in order to
347 specify more than one pattern. If a directory matches both <b>--include-dir</b>
348 and <b>--exclude-dir</b>, it is excluded. There is no short form for this
352 <b>-F</b>, <b>--fixed-strings</b>
353 Interpret each data-matching pattern as a list of fixed strings, separated by
354 newlines, instead of as a regular expression. What constitutes a newline for
355 this purpose is controlled by the <b>--newline</b> option. The <b>-w</b> (match
356 as a word) and <b>-x</b> (match whole line) options can be used with <b>-F</b>.
357 They apply to each of the fixed strings. A line is selected if any of the fixed
358 strings are found in it (subject to <b>-w</b> or <b>-x</b>, if present). This
359 option applies only to the patterns that are matched against the contents of
360 files; it does not apply to patterns specified by any of the <b>--include</b> or
361 <b>--exclude</b> options.
364 <b>-f</b> <i>filename</i>, <b>--file=</b><i>filename</i>
365 Read patterns from the file, one per line, and match them against each line of
366 input. As is the case with patterns on the command line, no delimiters should
367 be used. What constitutes a newline when reading the file is the operating
368 system's default interpretation of \n. The <b>--newline</b> option has no
369 effect on this option. Trailing white space is removed from each line, and
370 blank lines are ignored. An empty file contains no patterns and therefore
371 matches nothing. Patterns read from a file in this way may contain binary
372 zeros, which are treated as ordinary data characters. See also the comments
373 about multiple patterns versus a single pattern with alternatives in the
374 description of <b>-e</b> above.
377 If this option is given more than once, all the specified files are read. A
378 data line is output if any of the patterns match it. A file name can be given
379 as "-" to refer to the standard input. When <b>-f</b> is used, patterns
380 specified on the command line using <b>-e</b> may also be present; they are
381 tested before the file's patterns. However, no other pattern is taken from the
382 command line; all arguments are treated as the names of paths to be searched.
385 <b>--file-list</b>=<i>filename</i>
386 Read a list of files and/or directories that are to be scanned from the given
387 file, one per line. What constitutes a newline when reading the file is the
388 operating system's default. Trailing white space is removed from each line, and
389 blank lines are ignored. These paths are processed before any that are listed
390 on the command line. The file name can be given as "-" to refer to the standard
391 input. If <b>--file</b> and <b>--file-list</b> are both specified as "-",
392 patterns are read first. This is useful only when the standard input is a
393 terminal, from which further lines (the list of files) can be read after an
394 end-of-file indication. If this option is given more than once, all the
395 specified files are read.
398 <b>--file-offsets</b>
399 Instead of showing lines or parts of lines that match, show each match as an
400 offset from the start of the file and a length, separated by a comma. In this
401 mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b>
402 options are ignored. If there is more than one match in a line, each of them is
403 shown separately. This option is mutually exclusive with <b>--output</b>,
404 <b>--line-offsets</b>, and <b>--only-matching</b>.
407 <b>-H</b>, <b>--with-filename</b>
408 Force the inclusion of the file name at the start of output lines when
409 searching a single file. By default, the file name is not shown in this case.
410 For matching lines, the file name is followed by a colon; for context lines, a
411 hyphen separator is used. If a line number is also being output, it follows the
412 file name. When the <b>-M</b> option causes a pattern to match more than one
413 line, only the first is preceded by the file name. This option overrides any
414 previous <b>-h</b>, <b>-l</b>, or <b>-L</b> options.
417 <b>-h</b>, <b>--no-filename</b>
418 Suppress the output file names when searching multiple files. By default,
419 file names are shown when multiple files are searched. For matching lines, the
420 file name is followed by a colon; for context lines, a hyphen separator is used.
421 If a line number is also being output, it follows the file name. This option
422 overrides any previous <b>-H</b>, <b>-L</b>, or <b>-l</b> options.
425 <b>--heap-limit</b>=<i>number</i>
426 See <b>--match-limit</b> below.
430 Output a help message, giving brief details of the command options and file
431 type support, and then exit. Anything else on the command line is
436 Ignore binary files. This is equivalent to
437 <b>--binary-files</b>=<i>without-match</i>.
440 <b>-i</b>, <b>--ignore-case</b>
441 Ignore upper/lower case distinctions during comparisons.
444 <b>--include</b>=<i>pattern</i>
445 If any <b>--include</b> patterns are specified, the only files that are
446 processed are those that match one of the patterns (and do not match an
447 <b>--exclude</b> pattern). This option does not affect directories, but it
448 applies to all files, whether listed on the command line, obtained from
449 <b>--file-list</b>, or by scanning a directory. The pattern is a PCRE2 regular
450 expression, and is matched against the final component of the file name, not
451 the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not apply to
452 this pattern. The option may be given any number of times. If a file name
453 matches both an <b>--include</b> and an <b>--exclude</b> pattern, it is excluded.
454 There is no short form for this option.
457 <b>--include-from=</b><i>filename</i>
458 Treat each non-empty line of the file as the data for an <b>--include</b>
459 option. What constitutes a newline for this purpose is the operating system's
460 default. The <b>--newline</b> option has no effect on this option. This option
461 may be given any number of times; all the files are read.
464 <b>--include-dir</b>=<i>pattern</i>
465 If any <b>--include-dir</b> patterns are specified, the only directories that
466 are processed are those that match one of the patterns (and do not match an
467 <b>--exclude-dir</b> pattern). This applies to all directories, whether listed
468 on the command line, obtained from <b>--file-list</b>, or by scanning a parent
469 directory. The pattern is a PCRE2 regular expression, and is matched against
470 the final component of the directory name, not the entire path. The <b>-F</b>,
471 <b>-w</b>, and <b>-x</b> options do not apply to this pattern. The option may be
472 given any number of times. If a directory matches both <b>--include-dir</b> and
473 <b>--exclude-dir</b>, it is excluded. There is no short form for this option.
476 <b>-L</b>, <b>--files-without-match</b>
477 Instead of outputting lines from the files, just output the names of the files
478 that do not contain any lines that would have been output. Each file name is
479 output once, on a separate line. This option overrides any previous <b>-H</b>,
480 <b>-h</b>, or <b>-l</b> options.
483 <b>-l</b>, <b>--files-with-matches</b>
484 Instead of outputting lines from the files, just output the names of the files
485 containing lines that would have been output. Each file name is output once, on
486 a separate line. Searching normally stops as soon as a matching line is found
487 in a file. However, if the <b>-c</b> (count) option is also used, matching
488 continues in order to obtain the correct count, and those files that have at
489 least one match are listed along with their counts. Using this option with
490 <b>-c</b> is a way of suppressing the listing of files with no matches. This
491 opeion overrides any previous <b>-H</b>, <b>-h</b>, or <b>-L</b> options.
494 <b>--label</b>=<i>name</i>
495 This option supplies a name to be used for the standard input when file names
496 are being output. If not supplied, "(standard input)" is used. There is no
497 short form for this option.
500 <b>--line-buffered</b>
501 When this option is given, non-compressed input is read and processed line by
502 line, and the output is flushed after each write. By default, input is read in
503 large chunks, unless <b>pcre2grep</b> can determine that it is reading from a
504 terminal (which is currently possible only in Unix-like environments or
505 Windows). Output to terminal is normally automatically flushed by the operating
506 system. This option can be useful when the input or output is attached to a
507 pipe and you do not want <b>pcre2grep</b> to buffer up large amounts of data.
508 However, its use will affect performance, and the <b>-M</b> (multiline) option
509 ceases to work. When input is from a compressed .gz or .bz2 file,
510 <b>--line-buffered</b> is ignored.
513 <b>--line-offsets</b>
514 Instead of showing lines or parts of lines that match, show each match as a
515 line number, the offset from the start of the line, and a length. The line
516 number is terminated by a colon (as usual; see the <b>-n</b> option), and the
517 offset and length are separated by a comma. In this mode, no context is shown.
518 That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b> options are ignored. If there is
519 more than one match in a line, each of them is shown separately. This option is
520 mutually exclusive with <b>--output</b>, <b>--file-offsets</b>, and
521 <b>--only-matching</b>.
524 <b>--locale</b>=<i>locale-name</i>
525 This option specifies a locale to be used for pattern matching. It overrides
526 the value in the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variables. If no
527 locale is specified, the PCRE2 library's default (usually the "C" locale) is
528 used. There is no short form for this option.
531 <b>--match-limit</b>=<i>number</i>
532 Processing some regular expression patterns may take a very long time to search
533 for all possible matching strings. Others may require a very large amount of
534 memory. There are three options that set resource limits for matching.
537 The <b>--match-limit</b> option provides a means of limiting computing resource
538 usage when processing patterns that are not going to match, but which have a
539 very large number of possibilities in their search trees. The classic example
540 is a pattern that uses nested unlimited repeats. Internally, PCRE2 has a
541 counter that is incremented each time around its main processing loop. If the
542 value set by <b>--match-limit</b> is reached, an error occurs.
545 The <b>--heap-limit</b> option specifies, as a number of kibibytes (units of
546 1024 bytes), the amount of heap memory that may be used for matching. Heap
547 memory is needed only if matching the pattern requires a significant number of
548 nested backtracking points to be remembered. This parameter can be set to zero
549 to forbid the use of heap memory altogether.
552 The <b>--depth-limit</b> option limits the depth of nested backtracking points,
553 which indirectly limits the amount of memory that is used. The amount of memory
554 needed for each backtracking point depends on the number of capturing
555 parentheses in the pattern, so the amount of memory that is used before this
556 limit acts varies from pattern to pattern. This limit is of use only if it is
557 set smaller than <b>--match-limit</b>.
560 There are no short forms for these options. The default limits can be set
561 when the PCRE2 library is compiled; if they are not specified, the defaults
562 are very large and so effectively unlimited.
565 \fB--max-buffer-size=<i>number</i>
566 This limits the expansion of the processing buffer, whose initial size can be
567 set by <b>--buffer-size</b>. The maximum buffer size is silently forced to be no
568 smaller than the starting buffer size.
571 <b>-M</b>, <b>--multiline</b>
572 Allow patterns to match more than one line. When this option is set, the PCRE2
573 library is called in "multiline" mode. This allows a matched string to extend
574 past the end of a line and continue on one or more subsequent lines. Patterns
575 used with <b>-M</b> may usefully contain literal newline characters and internal
576 occurrences of ^ and $ characters. The output for a successful match may
577 consist of more than one line. The first line is the line in which the match
578 started, and the last line is the line in which the match ended. If the matched
579 string ends with a newline sequence, the output ends at the end of that line.
580 If <b>-v</b> is set, none of the lines in a multi-line match are output. Once a
581 match has been handled, scanning restarts at the beginning of the line after
582 the one in which the match ended.
585 The newline sequence that separates multiple lines must be matched as part of
586 the pattern. For example, to find the phrase "regular expression" in a file
587 where "regular" might be at the end of a line and "expression" at the start of
588 the next line, you could use this command:
590 pcre2grep -M 'regular\s+expression' <file>
592 The \s escape sequence matches any white space character, including newlines,
593 and is followed by + so as to match trailing white space on the first line as
594 well as possibly handling a two-character newline sequence.
597 There is a limit to the number of lines that can be matched, imposed by the way
598 that <b>pcre2grep</b> buffers the input file as it scans it. With a sufficiently
599 large processing buffer, this should not be a problem, but the <b>-M</b> option
600 does not work when input is read line by line (see \fP--line-buffered\fP.)
603 <b>-N</b> <i>newline-type</i>, <b>--newline</b>=<i>newline-type</i>
604 The PCRE2 library supports five different conventions for indicating
605 the ends of lines. They are the single-character sequences CR (carriage return)
606 and LF (linefeed), the two-character sequence CRLF, an "anycrlf" convention,
607 which recognizes any of the preceding three types, and an "any" convention, in
608 which any Unicode line ending sequence is assumed to end a line. The Unicode
609 sequences are the three just mentioned, plus VT (vertical tab, U+000B), FF
610 (form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and
611 PS (paragraph separator, U+2029).
614 When the PCRE2 library is built, a default line-ending sequence is specified.
615 This is normally the standard sequence for the operating system. Unless
616 otherwise specified by this option, <b>pcre2grep</b> uses the library's default.
617 The possible values for this option are CR, LF, CRLF, ANYCRLF, or ANY. This
618 makes it possible to use <b>pcre2grep</b> to scan files that have come from
619 other environments without having to modify their line endings. If the data
620 that is being scanned does not agree with the convention set by this option,
621 <b>pcre2grep</b> may behave in strange ways. Note that this option does not
622 apply to files specified by the <b>-f</b>, <b>--exclude-from</b>, or
623 <b>--include-from</b> options, which are expected to use the operating system's
624 standard newline sequence.
627 <b>-n</b>, <b>--line-number</b>
628 Precede each output line by its line number in the file, followed by a colon
629 for matching lines or a hyphen for context lines. If the file name is also
630 being output, it precedes the line number. When the <b>-M</b> option causes a
631 pattern to match more than one line, only the first is preceded by its line
632 number. This option is forced if <b>--line-offsets</b> is used.
636 If the PCRE2 library is built with support for just-in-time compiling (which
637 speeds up matching), <b>pcre2grep</b> automatically makes use of this, unless it
638 was explicitly disabled at build time. This option can be used to disable the
639 use of JIT at run time. It is provided for testing and working round problems.
640 It should never be needed in normal use.
643 <b>-O</b> <i>text</i>, <b>--output</b>=<i>text</i>
644 When there is a match, instead of outputting the whole line that matched,
645 output just the given text. This option is mutually exclusive with
646 <b>--only-matching</b>, <b>--file-offsets</b>, and <b>--line-offsets</b>. Escape
647 sequences starting with a dollar character may be used to insert the contents
648 of the matched part of the line and/or captured substrings into the text.
651 $<digits> or ${<digits>} is replaced by the captured
652 substring of the given decimal number; zero substitutes the whole match. If
653 the number is greater than the number of capturing substrings, or if the
654 capture is unset, the replacement is empty.
657 $a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by
658 newline; $r by carriage return; $t by tab; $v by vertical tab.
661 $o<digits> is replaced by the character represented by the given octal
662 number; up to three digits are processed.
665 $x<digits> is replaced by the character represented by the given hexadecimal
666 number; up to two digits are processed.
669 Any other character is substituted by itself. In particular, $$ is replaced by
673 <b>-o</b>, <b>--only-matching</b>
674 Show only the part of the line that matched a pattern instead of the whole
675 line. In this mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and
676 <b>-C</b> options are ignored. If there is more than one match in a line, each
677 of them is shown separately, on a separate line of output. If <b>-o</b> is
678 combined with <b>-v</b> (invert the sense of the match to find non-matching
679 lines), no output is generated, but the return code is set appropriately. If
680 the matched portion of the line is empty, nothing is output unless the file
681 name or line number are being printed, in which case they are shown on an
682 otherwise empty line. This option is mutually exclusive with <b>--output</b>,
683 <b>--file-offsets</b> and <b>--line-offsets</b>.
686 <b>-o</b><i>number</i>, <b>--only-matching</b>=<i>number</i>
687 Show only the part of the line that matched the capturing parentheses of the
688 given number. Up to 32 capturing parentheses are supported, and -o0 is
689 equivalent to <b>-o</b> without a number. Because these options can be given
690 without an argument (see above), if an argument is present, it must be given in
691 the same shell item, for example, -o3 or --only-matching=2. The comments given
692 for the non-argument case above also apply to this option. If the specified
693 capturing parentheses do not exist in the pattern, or were not set in the
694 match, nothing is output unless the file name or line number are being output.
697 If this option is given multiple times, multiple substrings are output for each
698 match, in the order the options are given, and all on one line. For example,
699 -o3 -o1 -o3 causes the substrings matched by capturing parentheses 3 and 1 and
700 then 3 again to be output. By default, there is no separator (but see the next
704 <b>--om-separator</b>=<i>text</i>
705 Specify a separating string for multiple occurrences of <b>-o</b>. The default
706 is an empty string. Separating strings are never coloured.
709 <b>-q</b>, <b>--quiet</b>
710 Work quietly, that is, display nothing except error messages. The exit
711 status indicates whether or not any matches were found.
714 <b>-r</b>, <b>--recursive</b>
715 If any given path is a directory, recursively scan the files it contains,
716 taking note of any <b>--include</b> and <b>--exclude</b> settings. By default, a
717 directory is read as a normal file; in some operating systems this gives an
718 immediate end-of-file. This option is a shorthand for setting the <b>-d</b>
722 <b>--recursion-limit</b>=<i>number</i>
723 See <b>--match-limit</b> above.
726 <b>-s</b>, <b>--no-messages</b>
727 Suppress error messages about non-existent or unreadable files. Such files are
728 quietly skipped. However, the return code is still 2, even if matches were
729 found in other files.
732 <b>-t</b>, <b>--total-count</b>
733 This option is useful when scanning more than one file. If used on its own,
734 <b>-t</b> suppresses all output except for a grand total number of matching
735 lines (or non-matching lines if <b>-v</b> is used) in all the files. If <b>-t</b>
736 is used with <b>-c</b>, a grand total is output except when the previous output
737 is just one line. In other words, it is not output when just one file's count
738 is listed. If file names are being output, the grand total is preceded by
739 "TOTAL:". Otherwise, it appears as just another number. The <b>-t</b> option is
740 ignored when used with <b>-L</b> (list files without matches), because the grand
741 total would always be zero.
744 <b>-u</b>, <b>--utf-8</b>
745 Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled
746 with UTF-8 support. All patterns (including those for any <b>--exclude</b> and
747 <b>--include</b> options) and all subject lines that are scanned must be valid
748 strings of UTF-8 characters.
751 <b>-V</b>, <b>--version</b>
752 Write the version numbers of <b>pcre2grep</b> and the PCRE2 library to the
753 standard output and then exit. Anything else on the command line is
757 <b>-v</b>, <b>--invert-match</b>
758 Invert the sense of the match, so that lines which do <i>not</i> match any of
759 the patterns are the ones that are found.
762 <b>-w</b>, <b>--word-regex</b>, <b>--word-regexp</b>
763 Force the patterns only to match "words". That is, there must be a word
764 boundary at the start and end of each matched string. This is equivalent to
765 having "\b(?:" at the start of each pattern, and ")\b" at the end. This
766 option applies only to the patterns that are matched against the contents of
767 files; it does not apply to patterns specified by any of the <b>--include</b> or
768 <b>--exclude</b> options.
771 <b>-x</b>, <b>--line-regex</b>, <b>--line-regexp</b>
772 Force the patterns to start matching only at the beginnings of lines, and in
773 addition, require them to match entire lines. In multiline mode the match may
774 be more than one line. This is equivalent to having "^(?:" at the start of each
775 pattern and ")$" at the end. This option applies only to the patterns that are
776 matched against the contents of files; it does not apply to patterns specified
777 by any of the <b>--include</b> or <b>--exclude</b> options.
779 <br><a name="SEC7" href="#TOC1">ENVIRONMENT VARIABLES</a><br>
781 The environment variables <b>LC_ALL</b> and <b>LC_CTYPE</b> are examined, in that
782 order, for a locale. The first one that is set is used. This can be overridden
783 by the <b>--locale</b> option. If no locale is set, the PCRE2 library's default
784 (usually the "C" locale) is used.
786 <br><a name="SEC8" href="#TOC1">NEWLINES</a><br>
788 The <b>-N</b> (<b>--newline</b>) option allows <b>pcre2grep</b> to scan files with
789 different newline conventions from the default. Any parts of the input files
790 that are written to the standard output are copied identically, with whatever
791 newline sequences they have in the input. However, the setting of this option
792 affects only the way scanned files are processed. It does not affect the
793 interpretation of files specified by the <b>-f</b>, <b>--file-list</b>,
794 <b>--exclude-from</b>, or <b>--include-from</b> options, nor does it affect the
795 way in which <b>pcre2grep</b> writes informational messages to the standard
796 error and output streams. For these it uses the string "\n" to indicate
797 newlines, relying on the C I/O library to convert this to an appropriate
800 <br><a name="SEC9" href="#TOC1">OPTIONS COMPATIBILITY</a><br>
802 Many of the short and long forms of <b>pcre2grep</b>'s options are the same
803 as in the GNU <b>grep</b> program. Any long option of the form
804 <b>--xxx-regexp</b> (GNU terminology) is also available as <b>--xxx-regex</b>
805 (PCRE2 terminology). However, the <b>--depth-limit</b>, <b>--file-list</b>,
806 <b>--file-offsets</b>, <b>--heap-limit</b>, <b>--include-dir</b>,
807 <b>--line-offsets</b>, <b>--locale</b>, <b>--match-limit</b>, <b>-M</b>,
808 <b>--multiline</b>, <b>-N</b>, <b>--newline</b>, <b>--om-separator</b>,
809 <b>--output</b>, <b>-u</b>, and <b>--utf-8</b> options are specific to
810 <b>pcre2grep</b>, as is the use of the <b>--only-matching</b> option with a
811 capturing parentheses number.
814 Although most of the common options work the same way, a few are different in
815 <b>pcre2grep</b>. For example, the <b>--include</b> option's argument is a glob
816 for GNU <b>grep</b>, but a regular expression for <b>pcre2grep</b>. If both the
817 <b>-c</b> and <b>-l</b> options are given, GNU grep lists only file names,
818 without counts, but <b>pcre2grep</b> gives the counts as well.
820 <br><a name="SEC10" href="#TOC1">OPTIONS WITH DATA</a><br>
822 There are four different ways in which an option with data can be specified.
823 If a short form option is used, the data may follow immediately, or (with one
824 exception) in the next command line item. For example:
829 The exception is the <b>-o</b> option, which may appear with or without data.
830 Because of this, if data is present, it must follow immediately in the same
831 item, for example -o3.
834 If a long form option is used, the data may appear in the same command line
835 item, separated by an equals character, or (with two exceptions) it may appear
836 in the next command line item. For example:
841 Note, however, that if you want to supply a file name beginning with ~ as data
842 in a shell command, and have the shell expand ~ to a home directory, you must
843 separate the file name from the option, because the shell does not treat ~
844 specially unless it is at the start of an item.
847 The exceptions to the above are the <b>--colour</b> (or <b>--color</b>) and
848 <b>--only-matching</b> options, for which the data is optional. If one of these
849 options does have data, it must be given in the first form, using an equals
850 character. Otherwise <b>pcre2grep</b> will assume that it has no data.
852 <br><a name="SEC11" href="#TOC1">USING PCRE2'S CALLOUT FACILITY</a><br>
854 <b>pcre2grep</b> has, by default, support for calling external programs or
855 scripts or echoing specific strings during matching by making use of PCRE2's
856 callout facility. However, this support can be disabled when <b>pcre2grep</b> is
857 built. You can find out whether your binary has support for callouts by running
858 it with the <b>--help</b> option. If the support is not enabled, all callouts in
859 patterns are ignored by <b>pcre2grep</b>.
862 A callout in a PCRE2 pattern is of the form (?C<arg>) where the argument is
863 either a number or a quoted string (see the
864 <a href="pcre2callout.html"><b>pcre2callout</b></a>
865 documentation for details). Numbered callouts are ignored by <b>pcre2grep</b>;
866 only callouts with string arguments are useful.
869 Calling external programs or scripts
872 If the callout string does not start with a pipe (vertical bar) character, it
873 is parsed into a list of substrings separated by pipe characters. The first
874 substring must be an executable name, with the following substrings specifying
877 executable_name|arg1|arg2|...
879 Any substring (including the executable name) may contain escape sequences
880 started by a dollar character: $<digits> or ${<digits>} is replaced by the
881 captured substring of the given decimal number, which must be greater than
882 zero. If the number is greater than the number of capturing substrings, or if
883 the capture is unset, the replacement is empty.
886 Any other character is substituted by itself. In particular, $$ is replaced by
887 a single dollar and $| is replaced by a pipe character. Here is an example:
889 echo -e "abcde\n12345" | pcre2grep \
891 (?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
895 Arg1: [a] [bcd] [d] Arg2: |a| ()
897 Arg1: [1] [234] [4] Arg2: |1| ()
900 The parameters for the <b>execv()</b> system call that is used to run the
901 program or script are zero-terminated strings. This means that binary zero
902 characters in the callout argument will cause premature termination of their
903 substrings, and therefore should not be present. Any syntax errors in the
904 string (for example, a dollar not followed by another character) cause the
905 callout to be ignored. If running the program fails for any reason (including
906 the non-existence of the executable), a local matching failure occurs and the
907 matcher backtracks in the normal way.
910 Echoing a specific string
913 If the callout string starts with a pipe (vertical bar) character, the rest of
914 the string is written to the output, having been passed through the same escape
915 processing as text from the --output option. This provides a simple echoing
916 facility that avoids calling an external program or script. No terminator is
917 added to the string, so if you want a newline, you must include it explicitly.
918 Matching continues normally after the string is output. If you want to see only
919 the callout output but not any output from an actual match, you should end the
920 relevant pattern with (*FAIL).
922 <br><a name="SEC12" href="#TOC1">MATCHING ERRORS</a><br>
924 It is possible to supply a regular expression that takes a very long time to
925 fail to match certain lines. Such patterns normally involve nested indefinite
926 repeats, for example: (a+)*\d when matched against a line of a's with no final
927 digit. The PCRE2 matching function has a resource limit that causes it to abort
928 in these circumstances. If this happens, <b>pcre2grep</b> outputs an error
929 message and the line that caused the problem to the standard error stream. If
930 there are more than 20 such errors, <b>pcre2grep</b> gives up.
933 The <b>--match-limit</b> option of <b>pcre2grep</b> can be used to set the
934 overall resource limit. There are also other limits that affect the amount of
935 memory used during matching; see the discussion of <b>--heap-limit</b> and
936 <b>--depth-limit</b> above.
938 <br><a name="SEC13" href="#TOC1">DIAGNOSTICS</a><br>
940 Exit status is 0 if any matches were found, 1 if no matches were found, and 2
941 for syntax errors, overlong lines, non-existent or inaccessible files (even if
942 matches were found in other files) or too many matching errors. Using the
943 <b>-s</b> option to suppress error messages about inaccessible files does not
944 affect the return code.
947 When run under VMS, the return code is placed in the symbol PCRE2GREP_RC
948 because VMS does not distinguish between exit(0) and exit(1).
950 <br><a name="SEC14" href="#TOC1">SEE ALSO</a><br>
952 <b>pcre2pattern</b>(3), <b>pcre2syntax</b>(3), <b>pcre2callout</b>(3).
954 <br><a name="SEC15" href="#TOC1">AUTHOR</a><br>
958 University Computing Service
963 <br><a name="SEC16" href="#TOC1">REVISION</a><br>
965 Last updated: 24 February 2018
967 Copyright © 1997-2018 University of Cambridge.
970 Return to the <a href="index.html">PCRE2 index page</a>.
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