pcre2grep.html 51 KB

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  1. <html>
  2. <head>
  3. <title>pcre2grep specification</title>
  4. </head>
  5. <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
  6. <h1>pcre2grep man page</h1>
  7. <p>
  8. Return to the <a href="index.html">PCRE2 index page</a>.
  9. </p>
  10. <p>
  11. This page is part of the PCRE2 HTML documentation. It was generated
  12. automatically from the original man page. If there is any nonsense in it,
  13. please consult the man page, in case the conversion went wrong.
  14. <br>
  15. <ul>
  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>
  32. </ul>
  33. <br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br>
  34. <P>
  35. <b>pcre2grep [options] [long options] [pattern] [path1 path2 ...]</b>
  36. </P>
  37. <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
  38. <P>
  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
  46. that PCRE2 supports.
  47. </P>
  48. <P>
  49. Patterns, whether supplied on the command line or in a separate file, are given
  50. without delimiters. For example:
  51. <pre>
  52. pcre2grep Thursday /etc/motd
  53. </pre>
  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.
  59. </P>
  60. <P>
  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.
  66. </P>
  67. <P>
  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.
  70. For example:
  71. <pre>
  72. pcre2grep some-pattern file1 - file3
  73. </pre>
  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.
  81. </P>
  82. <P>
  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
  92. longer be expanded.
  93. </P>
  94. <P>
  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.
  98. </P>
  99. <P>
  100. Patterns can be no longer than 8KiB or BUFSIZ bytes, whichever is the greater.
  101. BUFSIZ is defined in <b>&#60;stdio.h&#62;</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.
  105. </P>
  106. <P>
  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
  115. matched part of the line.
  116. </P>
  117. <P>
  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).
  122. </P>
  123. <P>
  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.
  129. </P>
  130. <P>
  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.
  134. </P>
  135. <br><a name="SEC3" href="#TOC1">SUPPORT FOR COMPRESSED FILES</a><br>
  136. <P>
  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
  144. ignored.
  145. </P>
  146. <br><a name="SEC4" href="#TOC1">BINARY FILES</a><br>
  147. <P>
  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. However, if the
  150. newline type is specified as NUL, that is, the line terminator is a binary
  151. zero, the test for a binary file is not applied. See the <b>--binary-files</b>
  152. option for a means of changing the way binary files are handled.
  153. </P>
  154. <br><a name="SEC5" href="#TOC1">BINARY ZEROS IN PATTERNS</a><br>
  155. <P>
  156. Patterns passed from the command line are strings that are terminated by a
  157. binary zero, so cannot contain internal zeros. However, patterns that are read
  158. from a file via the <b>-f</b> option may contain binary zeros.
  159. </P>
  160. <br><a name="SEC6" href="#TOC1">OPTIONS</a><br>
  161. <P>
  162. The order in which some of the options appear can affect the output. For
  163. example, both the <b>-H</b> and <b>-l</b> options affect the printing of file
  164. names. Whichever comes later in the command line will be the one that takes
  165. effect. Similarly, except where noted below, if an option is given twice, the
  166. later setting is used. Numerical values for options may be followed by K or M,
  167. to signify multiplication by 1024 or 1024*1024 respectively.
  168. </P>
  169. <P>
  170. <b>--</b>
  171. This terminates the list of options. It is useful if the next item on the
  172. command line starts with a hyphen but is not an option. This allows for the
  173. processing of patterns and file names that start with hyphens.
  174. </P>
  175. <P>
  176. <b>-A</b> <i>number</i>, <b>--after-context=</b><i>number</i>
  177. Output up to <i>number</i> lines of context after each matching line. Fewer
  178. lines are output if the next match or the end of the file is reached, or if the
  179. processing buffer size has been set too small. If file names and/or line
  180. numbers are being output, a hyphen separator is used instead of a colon for the
  181. context lines. A line containing "--" is output between each group of lines,
  182. unless they are in fact contiguous in the input file. The value of <i>number</i>
  183. is expected to be relatively small. When <b>-c</b> is used, <b>-A</b> is ignored.
  184. </P>
  185. <P>
  186. <b>-a</b>, <b>--text</b>
  187. Treat binary files as text. This is equivalent to
  188. <b>--binary-files</b>=<i>text</i>.
  189. </P>
  190. <P>
  191. <b>--allow-lookaround-bsk</b>
  192. PCRE2 now forbids the use of \K in lookarounds by default, in line with Perl.
  193. This option causes <b>pcre2grep</b> to set the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
  194. option, which enables this somewhat dangerous usage.
  195. </P>
  196. <P>
  197. <b>-B</b> <i>number</i>, <b>--before-context=</b><i>number</i>
  198. Output up to <i>number</i> lines of context before each matching line. Fewer
  199. lines are output if the previous match or the start of the file is within
  200. <i>number</i> lines, or if the processing buffer size has been set too small. If
  201. file names and/or line numbers are being output, a hyphen separator is used
  202. instead of a colon for the context lines. A line containing "--" is output
  203. between each group of lines, unless they are in fact contiguous in the input
  204. file. The value of <i>number</i> is expected to be relatively small. When
  205. <b>-c</b> is used, <b>-B</b> is ignored.
  206. </P>
  207. <P>
  208. <b>--binary-files=</b><i>word</i>
  209. Specify how binary files are to be processed. If the word is "binary" (the
  210. default), pattern matching is performed on binary files, but the only output is
  211. "Binary file &#60;name&#62; matches" when a match succeeds. If the word is "text",
  212. which is equivalent to the <b>-a</b> or <b>--text</b> option, binary files are
  213. processed in the same way as any other file. In this case, when a match
  214. succeeds, the output may be binary garbage, which can have nasty effects if
  215. sent to a terminal. If the word is "without-match", which is equivalent to the
  216. <b>-I</b> option, binary files are not processed at all; they are assumed not to
  217. be of interest and are skipped without causing any output or affecting the
  218. return code.
  219. </P>
  220. <P>
  221. <b>--buffer-size=</b><i>number</i>
  222. Set the parameter that controls how much memory is obtained at the start of
  223. processing for buffering files that are being scanned. See also
  224. <b>--max-buffer-size</b> below.
  225. </P>
  226. <P>
  227. <b>-C</b> <i>number</i>, <b>--context=</b><i>number</i>
  228. Output <i>number</i> lines of context both before and after each matching line.
  229. This is equivalent to setting both <b>-A</b> and <b>-B</b> to the same value.
  230. </P>
  231. <P>
  232. <b>-c</b>, <b>--count</b>
  233. Do not output lines from the files that are being scanned; instead output the
  234. number of lines that would have been shown, either because they matched, or, if
  235. <b>-v</b> is set, because they failed to match. By default, this count is
  236. exactly the same as the number of lines that would have been output, but if the
  237. <b>-M</b> (multiline) option is used (without <b>-v</b>), there may be more
  238. suppressed lines than the count (that is, the number of matches).
  239. <br>
  240. <br>
  241. If no lines are selected, the number zero is output. If several files are are
  242. being scanned, a count is output for each of them and the <b>-t</b> option can
  243. be used to cause a total to be output at the end. However, if the
  244. <b>--files-with-matches</b> option is also used, only those files whose counts
  245. are greater than zero are listed. When <b>-c</b> is used, the <b>-A</b>,
  246. <b>-B</b>, and <b>-C</b> options are ignored.
  247. </P>
  248. <P>
  249. <b>--colour</b>, <b>--color</b>
  250. If this option is given without any data, it is equivalent to "--colour=auto".
  251. If data is required, it must be given in the same shell item, separated by an
  252. equals sign.
  253. </P>
  254. <P>
  255. <b>--colour=</b><i>value</i>, <b>--color=</b><i>value</i>
  256. This option specifies under what circumstances the parts of a line that matched
  257. a pattern should be coloured in the output. By default, the output is not
  258. coloured. The value (which is optional, see above) may be "never", "always", or
  259. "auto". In the latter case, colouring happens only if the standard output is
  260. connected to a terminal. More resources are used when colouring is enabled,
  261. because <b>pcre2grep</b> has to search for all possible matches in a line, not
  262. just one, in order to colour them all.
  263. <br>
  264. <br>
  265. The colour that is used can be specified by setting one of the environment
  266. variables PCRE2GREP_COLOUR, PCRE2GREP_COLOR, PCREGREP_COLOUR, or
  267. PCREGREP_COLOR, which are checked in that order. If none of these are set,
  268. <b>pcre2grep</b> looks for GREP_COLORS or GREP_COLOR (in that order). The value
  269. of the variable should be a string of two numbers, separated by a semicolon,
  270. except in the case of GREP_COLORS, which must start with "ms=" or "mt="
  271. followed by two semicolon-separated colours, terminated by the end of the
  272. string or by a colon. If GREP_COLORS does not start with "ms=" or "mt=" it is
  273. ignored, and GREP_COLOR is checked.
  274. <br>
  275. <br>
  276. If the string obtained from one of the above variables contains any characters
  277. other than semicolon or digits, the setting is ignored and the default colour
  278. is used. The string is copied directly into the control string for setting
  279. colour on a terminal, so it is your responsibility to ensure that the values
  280. make sense. If no relevant environment variable is set, the default is "1;31",
  281. which gives red.
  282. </P>
  283. <P>
  284. <b>-D</b> <i>action</i>, <b>--devices=</b><i>action</i>
  285. If an input path is not a regular file or a directory, "action" specifies how
  286. it is to be processed. Valid values are "read" (the default) or "skip"
  287. (silently skip the path).
  288. </P>
  289. <P>
  290. <b>-d</b> <i>action</i>, <b>--directories=</b><i>action</i>
  291. If an input path is a directory, "action" specifies how it is to be processed.
  292. Valid values are "read" (the default in non-Windows environments, for
  293. compatibility with GNU grep), "recurse" (equivalent to the <b>-r</b> option), or
  294. "skip" (silently skip the path, the default in Windows environments). In the
  295. "read" case, directories are read as if they were ordinary files. In some
  296. operating systems the effect of reading a directory like this is an immediate
  297. end-of-file; in others it may provoke an error.
  298. </P>
  299. <P>
  300. <b>--depth-limit</b>=<i>number</i>
  301. See <b>--match-limit</b> below.
  302. </P>
  303. <P>
  304. <b>-e</b> <i>pattern</i>, <b>--regex=</b><i>pattern</i>, <b>--regexp=</b><i>pattern</i>
  305. Specify a pattern to be matched. This option can be used multiple times in
  306. order to specify several patterns. It can also be used as a way of specifying a
  307. single pattern that starts with a hyphen. When <b>-e</b> is used, no argument
  308. pattern is taken from the command line; all arguments are treated as file
  309. names. There is no limit to the number of patterns. They are applied to each
  310. line in the order in which they are defined until one matches.
  311. <br>
  312. <br>
  313. If <b>-f</b> is used with <b>-e</b>, the command line patterns are matched first,
  314. followed by the patterns from the file(s), independent of the order in which
  315. these options are specified. Note that multiple use of <b>-e</b> is not the same
  316. as a single pattern with alternatives. For example, X|Y finds the first
  317. character in a line that is X or Y, whereas if the two patterns are given
  318. separately, with X first, <b>pcre2grep</b> finds X if it is present, even if it
  319. follows Y in the line. It finds Y only if there is no X in the line. This
  320. matters only if you are using <b>-o</b> or <b>--colo(u)r</b> to show the part(s)
  321. of the line that matched.
  322. </P>
  323. <P>
  324. <b>--exclude</b>=<i>pattern</i>
  325. Files (but not directories) whose names match the pattern are skipped without
  326. being processed. This applies to all files, whether listed on the command line,
  327. obtained from <b>--file-list</b>, or by scanning a directory. The pattern is a
  328. PCRE2 regular expression, and is matched against the final component of the
  329. file name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do
  330. not apply to this pattern. The option may be given any number of times in order
  331. to specify multiple patterns. If a file name matches both an <b>--include</b>
  332. and an <b>--exclude</b> pattern, it is excluded. There is no short form for this
  333. option.
  334. </P>
  335. <P>
  336. <b>--exclude-from=</b><i>filename</i>
  337. Treat each non-empty line of the file as the data for an <b>--exclude</b>
  338. option. What constitutes a newline when reading the file is the operating
  339. system's default. The <b>--newline</b> option has no effect on this option. This
  340. option may be given more than once in order to specify a number of files to
  341. read.
  342. </P>
  343. <P>
  344. <b>--exclude-dir</b>=<i>pattern</i>
  345. Directories whose names match the pattern are skipped without being processed,
  346. whatever the setting of the <b>--recursive</b> option. This applies to all
  347. directories, whether listed on the command line, obtained from
  348. <b>--file-list</b>, or by scanning a parent directory. The pattern is a PCRE2
  349. regular expression, and is matched against the final component of the directory
  350. name, not the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not
  351. apply to this pattern. The option may be given any number of times in order to
  352. specify more than one pattern. If a directory matches both <b>--include-dir</b>
  353. and <b>--exclude-dir</b>, it is excluded. There is no short form for this
  354. option.
  355. </P>
  356. <P>
  357. <b>-F</b>, <b>--fixed-strings</b>
  358. Interpret each data-matching pattern as a list of fixed strings, separated by
  359. newlines, instead of as a regular expression. What constitutes a newline for
  360. this purpose is controlled by the <b>--newline</b> option. The <b>-w</b> (match
  361. as a word) and <b>-x</b> (match whole line) options can be used with <b>-F</b>.
  362. They apply to each of the fixed strings. A line is selected if any of the fixed
  363. strings are found in it (subject to <b>-w</b> or <b>-x</b>, if present). This
  364. option applies only to the patterns that are matched against the contents of
  365. files; it does not apply to patterns specified by any of the <b>--include</b> or
  366. <b>--exclude</b> options.
  367. </P>
  368. <P>
  369. <b>-f</b> <i>filename</i>, <b>--file=</b><i>filename</i>
  370. Read patterns from the file, one per line, and match them against each line of
  371. input. As is the case with patterns on the command line, no delimiters should
  372. be used. What constitutes a newline when reading the file is the operating
  373. system's default interpretation of \n. The <b>--newline</b> option has no
  374. effect on this option. Trailing white space is removed from each line, and
  375. blank lines are ignored. An empty file contains no patterns and therefore
  376. matches nothing. Patterns read from a file in this way may contain binary
  377. zeros, which are treated as ordinary data characters. See also the comments
  378. about multiple patterns versus a single pattern with alternatives in the
  379. description of <b>-e</b> above.
  380. <br>
  381. <br>
  382. If this option is given more than once, all the specified files are read. A
  383. data line is output if any of the patterns match it. A file name can be given
  384. as "-" to refer to the standard input. When <b>-f</b> is used, patterns
  385. specified on the command line using <b>-e</b> may also be present; they are
  386. tested before the file's patterns. However, no other pattern is taken from the
  387. command line; all arguments are treated as the names of paths to be searched.
  388. </P>
  389. <P>
  390. <b>--file-list</b>=<i>filename</i>
  391. Read a list of files and/or directories that are to be scanned from the given
  392. file, one per line. What constitutes a newline when reading the file is the
  393. operating system's default. Trailing white space is removed from each line, and
  394. blank lines are ignored. These paths are processed before any that are listed
  395. on the command line. The file name can be given as "-" to refer to the standard
  396. input. If <b>--file</b> and <b>--file-list</b> are both specified as "-",
  397. patterns are read first. This is useful only when the standard input is a
  398. terminal, from which further lines (the list of files) can be read after an
  399. end-of-file indication. If this option is given more than once, all the
  400. specified files are read.
  401. </P>
  402. <P>
  403. <b>--file-offsets</b>
  404. Instead of showing lines or parts of lines that match, show each match as an
  405. offset from the start of the file and a length, separated by a comma. In this
  406. mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b>
  407. options are ignored. If there is more than one match in a line, each of them is
  408. shown separately. This option is mutually exclusive with <b>--output</b>,
  409. <b>--line-offsets</b>, and <b>--only-matching</b>.
  410. </P>
  411. <P>
  412. <b>-H</b>, <b>--with-filename</b>
  413. Force the inclusion of the file name at the start of output lines when
  414. searching a single file. By default, the file name is not shown in this case.
  415. For matching lines, the file name is followed by a colon; for context lines, a
  416. hyphen separator is used. If a line number is also being output, it follows the
  417. file name. When the <b>-M</b> option causes a pattern to match more than one
  418. line, only the first is preceded by the file name. This option overrides any
  419. previous <b>-h</b>, <b>-l</b>, or <b>-L</b> options.
  420. </P>
  421. <P>
  422. <b>-h</b>, <b>--no-filename</b>
  423. Suppress the output file names when searching multiple files. By default,
  424. file names are shown when multiple files are searched. For matching lines, the
  425. file name is followed by a colon; for context lines, a hyphen separator is used.
  426. If a line number is also being output, it follows the file name. This option
  427. overrides any previous <b>-H</b>, <b>-L</b>, or <b>-l</b> options.
  428. </P>
  429. <P>
  430. <b>--heap-limit</b>=<i>number</i>
  431. See <b>--match-limit</b> below.
  432. </P>
  433. <P>
  434. <b>--help</b>
  435. Output a help message, giving brief details of the command options and file
  436. type support, and then exit. Anything else on the command line is
  437. ignored.
  438. </P>
  439. <P>
  440. <b>-I</b>
  441. Ignore binary files. This is equivalent to
  442. <b>--binary-files</b>=<i>without-match</i>.
  443. </P>
  444. <P>
  445. <b>-i</b>, <b>--ignore-case</b>
  446. Ignore upper/lower case distinctions during comparisons.
  447. </P>
  448. <P>
  449. <b>--include</b>=<i>pattern</i>
  450. If any <b>--include</b> patterns are specified, the only files that are
  451. processed are those whose names match one of the patterns and do not match an
  452. <b>--exclude</b> pattern. This option does not affect directories, but it
  453. applies to all files, whether listed on the command line, obtained from
  454. <b>--file-list</b>, or by scanning a directory. The pattern is a PCRE2 regular
  455. expression, and is matched against the final component of the file name, not
  456. the entire path. The <b>-F</b>, <b>-w</b>, and <b>-x</b> options do not apply to
  457. this pattern. The option may be given any number of times. If a file name
  458. matches both an <b>--include</b> and an <b>--exclude</b> pattern, it is excluded.
  459. There is no short form for this option.
  460. </P>
  461. <P>
  462. <b>--include-from=</b><i>filename</i>
  463. Treat each non-empty line of the file as the data for an <b>--include</b>
  464. option. What constitutes a newline for this purpose is the operating system's
  465. default. The <b>--newline</b> option has no effect on this option. This option
  466. may be given any number of times; all the files are read.
  467. </P>
  468. <P>
  469. <b>--include-dir</b>=<i>pattern</i>
  470. If any <b>--include-dir</b> patterns are specified, the only directories that
  471. are processed are those whose names match one of the patterns and do not match
  472. an <b>--exclude-dir</b> pattern. This applies to all directories, whether listed
  473. on the command line, obtained from <b>--file-list</b>, or by scanning a parent
  474. directory. The pattern is a PCRE2 regular expression, and is matched against
  475. the final component of the directory name, not the entire path. The <b>-F</b>,
  476. <b>-w</b>, and <b>-x</b> options do not apply to this pattern. The option may be
  477. given any number of times. If a directory matches both <b>--include-dir</b> and
  478. <b>--exclude-dir</b>, it is excluded. There is no short form for this option.
  479. </P>
  480. <P>
  481. <b>-L</b>, <b>--files-without-match</b>
  482. Instead of outputting lines from the files, just output the names of the files
  483. that do not contain any lines that would have been output. Each file name is
  484. output once, on a separate line. This option overrides any previous <b>-H</b>,
  485. <b>-h</b>, or <b>-l</b> options.
  486. </P>
  487. <P>
  488. <b>-l</b>, <b>--files-with-matches</b>
  489. Instead of outputting lines from the files, just output the names of the files
  490. containing lines that would have been output. Each file name is output once, on
  491. a separate line. Searching normally stops as soon as a matching line is found
  492. in a file. However, if the <b>-c</b> (count) option is also used, matching
  493. continues in order to obtain the correct count, and those files that have at
  494. least one match are listed along with their counts. Using this option with
  495. <b>-c</b> is a way of suppressing the listing of files with no matches that
  496. occurs with <b>-c</b> on its own. This option overrides any previous <b>-H</b>,
  497. <b>-h</b>, or <b>-L</b> options.
  498. </P>
  499. <P>
  500. <b>--label</b>=<i>name</i>
  501. This option supplies a name to be used for the standard input when file names
  502. are being output. If not supplied, "(standard input)" is used. There is no
  503. short form for this option.
  504. </P>
  505. <P>
  506. <b>--line-buffered</b>
  507. When this option is given, non-compressed input is read and processed line by
  508. line, and the output is flushed after each write. By default, input is read in
  509. large chunks, unless <b>pcre2grep</b> can determine that it is reading from a
  510. terminal, which is currently possible only in Unix-like environments or
  511. Windows. Output to terminal is normally automatically flushed by the operating
  512. system. This option can be useful when the input or output is attached to a
  513. pipe and you do not want <b>pcre2grep</b> to buffer up large amounts of data.
  514. However, its use will affect performance, and the <b>-M</b> (multiline) option
  515. ceases to work. When input is from a compressed .gz or .bz2 file,
  516. <b>--line-buffered</b> is ignored.
  517. </P>
  518. <P>
  519. <b>--line-offsets</b>
  520. Instead of showing lines or parts of lines that match, show each match as a
  521. line number, the offset from the start of the line, and a length. The line
  522. number is terminated by a colon (as usual; see the <b>-n</b> option), and the
  523. offset and length are separated by a comma. In this mode, no context is shown.
  524. That is, the <b>-A</b>, <b>-B</b>, and <b>-C</b> options are ignored. If there is
  525. more than one match in a line, each of them is shown separately. This option is
  526. mutually exclusive with <b>--output</b>, <b>--file-offsets</b>, and
  527. <b>--only-matching</b>.
  528. </P>
  529. <P>
  530. <b>--locale</b>=<i>locale-name</i>
  531. This option specifies a locale to be used for pattern matching. It overrides
  532. the value in the <b>LC_ALL</b> or <b>LC_CTYPE</b> environment variables. If no
  533. locale is specified, the PCRE2 library's default (usually the "C" locale) is
  534. used. There is no short form for this option.
  535. </P>
  536. <P>
  537. <b>-M</b>, <b>--multiline</b>
  538. Allow patterns to match more than one line. When this option is set, the PCRE2
  539. library is called in "multiline" mode. This allows a matched string to extend
  540. past the end of a line and continue on one or more subsequent lines. Patterns
  541. used with <b>-M</b> may usefully contain literal newline characters and internal
  542. occurrences of ^ and $ characters. The output for a successful match may
  543. consist of more than one line. The first line is the line in which the match
  544. started, and the last line is the line in which the match ended. If the matched
  545. string ends with a newline sequence, the output ends at the end of that line.
  546. If <b>-v</b> is set, none of the lines in a multi-line match are output. Once a
  547. match has been handled, scanning restarts at the beginning of the line after
  548. the one in which the match ended.
  549. <br>
  550. <br>
  551. The newline sequence that separates multiple lines must be matched as part of
  552. the pattern. For example, to find the phrase "regular expression" in a file
  553. where "regular" might be at the end of a line and "expression" at the start of
  554. the next line, you could use this command:
  555. <pre>
  556. pcre2grep -M 'regular\s+expression' &#60;file&#62;
  557. </pre>
  558. The \s escape sequence matches any white space character, including newlines,
  559. and is followed by + so as to match trailing white space on the first line as
  560. well as possibly handling a two-character newline sequence.
  561. <br>
  562. <br>
  563. There is a limit to the number of lines that can be matched, imposed by the way
  564. that <b>pcre2grep</b> buffers the input file as it scans it. With a sufficiently
  565. large processing buffer, this should not be a problem, but the <b>-M</b> option
  566. does not work when input is read line by line (see <b>--line-buffered</b>.)
  567. </P>
  568. <P>
  569. <b>-m</b> <i>number</i>, <b>--max-count</b>=<i>number</i>
  570. Stop processing after finding <i>number</i> matching lines, or non-matching
  571. lines if <b>-v</b> is also set. Any trailing context lines are output after the
  572. final match. In multiline mode, each multiline match counts as just one line
  573. for this purpose. If this limit is reached when reading the standard input from
  574. a regular file, the file is left positioned just after the last matching line.
  575. If <b>-c</b> is also set, the count that is output is never greater than
  576. <i>number</i>. This option has no effect if used with <b>-L</b>, <b>-l</b>, or
  577. <b>-q</b>, or when just checking for a match in a binary file.
  578. </P>
  579. <P>
  580. <b>--match-limit</b>=<i>number</i>
  581. Processing some regular expression patterns may take a very long time to search
  582. for all possible matching strings. Others may require a very large amount of
  583. memory. There are three options that set resource limits for matching.
  584. <br>
  585. <br>
  586. The <b>--match-limit</b> option provides a means of limiting computing resource
  587. usage when processing patterns that are not going to match, but which have a
  588. very large number of possibilities in their search trees. The classic example
  589. is a pattern that uses nested unlimited repeats. Internally, PCRE2 has a
  590. counter that is incremented each time around its main processing loop. If the
  591. value set by <b>--match-limit</b> is reached, an error occurs.
  592. <br>
  593. <br>
  594. The <b>--heap-limit</b> option specifies, as a number of kibibytes (units of
  595. 1024 bytes), the amount of heap memory that may be used for matching. Heap
  596. memory is needed only if matching the pattern requires a significant number of
  597. nested backtracking points to be remembered. This parameter can be set to zero
  598. to forbid the use of heap memory altogether.
  599. <br>
  600. <br>
  601. The <b>--depth-limit</b> option limits the depth of nested backtracking points,
  602. which indirectly limits the amount of memory that is used. The amount of memory
  603. needed for each backtracking point depends on the number of capturing
  604. parentheses in the pattern, so the amount of memory that is used before this
  605. limit acts varies from pattern to pattern. This limit is of use only if it is
  606. set smaller than <b>--match-limit</b>.
  607. <br>
  608. <br>
  609. There are no short forms for these options. The default limits can be set
  610. when the PCRE2 library is compiled; if they are not specified, the defaults
  611. are very large and so effectively unlimited.
  612. </P>
  613. <P>
  614. <b>--max-buffer-size</b>=<i>number</i>
  615. This limits the expansion of the processing buffer, whose initial size can be
  616. set by <b>--buffer-size</b>. The maximum buffer size is silently forced to be no
  617. smaller than the starting buffer size.
  618. </P>
  619. <P>
  620. <b>-N</b> <i>newline-type</i>, <b>--newline</b>=<i>newline-type</i>
  621. Six different conventions for indicating the ends of lines in scanned files are
  622. supported. For example:
  623. <pre>
  624. pcre2grep -N CRLF 'some pattern' &#60;file&#62;
  625. </pre>
  626. The newline type may be specified in upper, lower, or mixed case. If the
  627. newline type is NUL, lines are separated by binary zero characters. The other
  628. types are the single-character sequences CR (carriage return) and LF
  629. (linefeed), the two-character sequence CRLF, an "anycrlf" type, which
  630. recognizes any of the preceding three types, and an "any" type, for which any
  631. Unicode line ending sequence is assumed to end a line. The Unicode sequences
  632. are the three just mentioned, plus VT (vertical tab, U+000B), FF (form feed,
  633. U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
  634. (paragraph separator, U+2029).
  635. <br>
  636. <br>
  637. When the PCRE2 library is built, a default line-ending sequence is specified.
  638. This is normally the standard sequence for the operating system. Unless
  639. otherwise specified by this option, <b>pcre2grep</b> uses the library's default.
  640. <br>
  641. <br>
  642. This option makes it possible to use <b>pcre2grep</b> to scan files that have
  643. come from other environments without having to modify their line endings. If
  644. the data that is being scanned does not agree with the convention set by this
  645. option, <b>pcre2grep</b> may behave in strange ways. Note that this option does
  646. not apply to files specified by the <b>-f</b>, <b>--exclude-from</b>, or
  647. <b>--include-from</b> options, which are expected to use the operating system's
  648. standard newline sequence.
  649. </P>
  650. <P>
  651. <b>-n</b>, <b>--line-number</b>
  652. Precede each output line by its line number in the file, followed by a colon
  653. for matching lines or a hyphen for context lines. If the file name is also
  654. being output, it precedes the line number. When the <b>-M</b> option causes a
  655. pattern to match more than one line, only the first is preceded by its line
  656. number. This option is forced if <b>--line-offsets</b> is used.
  657. </P>
  658. <P>
  659. <b>--no-jit</b>
  660. If the PCRE2 library is built with support for just-in-time compiling (which
  661. speeds up matching), <b>pcre2grep</b> automatically makes use of this, unless it
  662. was explicitly disabled at build time. This option can be used to disable the
  663. use of JIT at run time. It is provided for testing and working round problems.
  664. It should never be needed in normal use.
  665. </P>
  666. <P>
  667. <b>-O</b> <i>text</i>, <b>--output</b>=<i>text</i>
  668. When there is a match, instead of outputting the line that matched, output just
  669. the text specified in this option, followed by an operating-system standard
  670. newline. In this mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>,
  671. and <b>-C</b> options are ignored. The <b>--newline</b> option has no effect on
  672. this option, which is mutually exclusive with <b>--only-matching</b>,
  673. <b>--file-offsets</b>, and <b>--line-offsets</b>. However, like
  674. <b>--only-matching</b>, if there is more than one match in a line, each of them
  675. causes a line of output.
  676. <br>
  677. <br>
  678. Escape sequences starting with a dollar character may be used to insert the
  679. contents of the matched part of the line and/or captured substrings into the
  680. text.
  681. <br>
  682. <br>
  683. $&#60;digits&#62; or ${&#60;digits&#62;} is replaced by the captured substring of the given
  684. decimal number; zero substitutes the whole match. If the number is greater than
  685. the number of capturing substrings, or if the capture is unset, the replacement
  686. is empty.
  687. <br>
  688. <br>
  689. $a is replaced by bell; $b by backspace; $e by escape; $f by form feed; $n by
  690. newline; $r by carriage return; $t by tab; $v by vertical tab.
  691. <br>
  692. <br>
  693. $o&#60;digits&#62; or $o{&#60;digits&#62;} is replaced by the character whose code point is the
  694. given octal number. In the first form, up to three octal digits are processed.
  695. When more digits are needed in Unicode mode to specify a wide character, the
  696. second form must be used.
  697. <br>
  698. <br>
  699. $x&#60;digits&#62; or $x{&#60;digits&#62;} is replaced by the character represented by the
  700. given hexadecimal number. In the first form, up to two hexadecimal digits are
  701. processed. When more digits are needed in Unicode mode to specify a wide
  702. character, the second form must be used.
  703. <br>
  704. <br>
  705. Any other character is substituted by itself. In particular, $$ is replaced by
  706. a single dollar.
  707. </P>
  708. <P>
  709. <b>-o</b>, <b>--only-matching</b>
  710. Show only the part of the line that matched a pattern instead of the whole
  711. line. In this mode, no context is shown. That is, the <b>-A</b>, <b>-B</b>, and
  712. <b>-C</b> options are ignored. If there is more than one match in a line, each
  713. of them is shown separately, on a separate line of output. If <b>-o</b> is
  714. combined with <b>-v</b> (invert the sense of the match to find non-matching
  715. lines), no output is generated, but the return code is set appropriately. If
  716. the matched portion of the line is empty, nothing is output unless the file
  717. name or line number are being printed, in which case they are shown on an
  718. otherwise empty line. This option is mutually exclusive with <b>--output</b>,
  719. <b>--file-offsets</b> and <b>--line-offsets</b>.
  720. </P>
  721. <P>
  722. <b>-o</b><i>number</i>, <b>--only-matching</b>=<i>number</i>
  723. Show only the part of the line that matched the capturing parentheses of the
  724. given number. Up to 50 capturing parentheses are supported by default. This
  725. limit can be changed via the <b>--om-capture</b> option. A pattern may contain
  726. any number of capturing parentheses, but only those whose number is within the
  727. limit can be accessed by <b>-o</b>. An error occurs if the number specified by
  728. <b>-o</b> is greater than the limit.
  729. <br>
  730. <br>
  731. -o0 is the same as <b>-o</b> without a number. Because these options can be
  732. given without an argument (see above), if an argument is present, it must be
  733. given in the same shell item, for example, -o3 or --only-matching=2. The
  734. comments given for the non-argument case above also apply to this option. If
  735. the specified capturing parentheses do not exist in the pattern, or were not
  736. set in the match, nothing is output unless the file name or line number are
  737. being output.
  738. <br>
  739. <br>
  740. If this option is given multiple times, multiple substrings are output for each
  741. match, in the order the options are given, and all on one line. For example,
  742. -o3 -o1 -o3 causes the substrings matched by capturing parentheses 3 and 1 and
  743. then 3 again to be output. By default, there is no separator (but see the next
  744. but one option).
  745. </P>
  746. <P>
  747. <b>--om-capture</b>=<i>number</i>
  748. Set the number of capturing parentheses that can be accessed by <b>-o</b>. The
  749. default is 50.
  750. </P>
  751. <P>
  752. <b>--om-separator</b>=<i>text</i>
  753. Specify a separating string for multiple occurrences of <b>-o</b>. The default
  754. is an empty string. Separating strings are never coloured.
  755. </P>
  756. <P>
  757. <b>-q</b>, <b>--quiet</b>
  758. Work quietly, that is, display nothing except error messages. The exit
  759. status indicates whether or not any matches were found.
  760. </P>
  761. <P>
  762. <b>-r</b>, <b>--recursive</b>
  763. If any given path is a directory, recursively scan the files it contains,
  764. taking note of any <b>--include</b> and <b>--exclude</b> settings. By default, a
  765. directory is read as a normal file; in some operating systems this gives an
  766. immediate end-of-file. This option is a shorthand for setting the <b>-d</b>
  767. option to "recurse".
  768. </P>
  769. <P>
  770. <b>--recursion-limit</b>=<i>number</i>
  771. This is an obsolete synonym for <b>--depth-limit</b>. See <b>--match-limit</b>
  772. above for details.
  773. </P>
  774. <P>
  775. <b>-s</b>, <b>--no-messages</b>
  776. Suppress error messages about non-existent or unreadable files. Such files are
  777. quietly skipped. However, the return code is still 2, even if matches were
  778. found in other files.
  779. </P>
  780. <P>
  781. <b>-t</b>, <b>--total-count</b>
  782. This option is useful when scanning more than one file. If used on its own,
  783. <b>-t</b> suppresses all output except for a grand total number of matching
  784. lines (or non-matching lines if <b>-v</b> is used) in all the files. If <b>-t</b>
  785. is used with <b>-c</b>, a grand total is output except when the previous output
  786. is just one line. In other words, it is not output when just one file's count
  787. is listed. If file names are being output, the grand total is preceded by
  788. "TOTAL:". Otherwise, it appears as just another number. The <b>-t</b> option is
  789. ignored when used with <b>-L</b> (list files without matches), because the grand
  790. total would always be zero.
  791. </P>
  792. <P>
  793. <b>-u</b>, <b>--utf</b>
  794. Operate in UTF-8 mode. This option is available only if PCRE2 has been compiled
  795. with UTF-8 support. All patterns (including those for any <b>--exclude</b> and
  796. <b>--include</b> options) and all lines that are scanned must be valid strings
  797. of UTF-8 characters. If an invalid UTF-8 string is encountered, an error
  798. occurs.
  799. </P>
  800. <P>
  801. <b>-U</b>, <b>--utf-allow-invalid</b>
  802. As <b>--utf</b>, but in addition subject lines may contain invalid UTF-8 code
  803. unit sequences. These can never form part of any pattern match. Patterns
  804. themselves, however, must still be valid UTF-8 strings. This facility allows
  805. valid UTF-8 strings to be sought within arbitrary byte sequences in executable
  806. or other binary files. For more details about matching in non-valid UTF-8
  807. strings, see the
  808. <a href="pcre2unicode.html"><b>pcre2unicode</b>(3)</a>
  809. documentation.
  810. </P>
  811. <P>
  812. <b>-V</b>, <b>--version</b>
  813. Write the version numbers of <b>pcre2grep</b> and the PCRE2 library to the
  814. standard output and then exit. Anything else on the command line is
  815. ignored.
  816. </P>
  817. <P>
  818. <b>-v</b>, <b>--invert-match</b>
  819. Invert the sense of the match, so that lines which do <i>not</i> match any of
  820. the patterns are the ones that are found. When this option is set, options such
  821. as <b>--only-matching</b> and <b>--output</b>, which specify parts of a match
  822. that are to be output, are ignored.
  823. </P>
  824. <P>
  825. <b>-w</b>, <b>--word-regex</b>, <b>--word-regexp</b>
  826. Force the patterns only to match "words". That is, there must be a word
  827. boundary at the start and end of each matched string. This is equivalent to
  828. having "\b(?:" at the start of each pattern, and ")\b" at the end. This
  829. option applies only to the patterns that are matched against the contents of
  830. files; it does not apply to patterns specified by any of the <b>--include</b> or
  831. <b>--exclude</b> options.
  832. </P>
  833. <P>
  834. <b>-x</b>, <b>--line-regex</b>, <b>--line-regexp</b>
  835. Force the patterns to start matching only at the beginnings of lines, and in
  836. addition, require them to match entire lines. In multiline mode the match may
  837. be more than one line. This is equivalent to having "^(?:" at the start of each
  838. pattern and ")$" at the end. This option applies only to the patterns that are
  839. matched against the contents of files; it does not apply to patterns specified
  840. by any of the <b>--include</b> or <b>--exclude</b> options.
  841. </P>
  842. <br><a name="SEC7" href="#TOC1">ENVIRONMENT VARIABLES</a><br>
  843. <P>
  844. The environment variables <b>LC_ALL</b> and <b>LC_CTYPE</b> are examined, in that
  845. order, for a locale. The first one that is set is used. This can be overridden
  846. by the <b>--locale</b> option. If no locale is set, the PCRE2 library's default
  847. (usually the "C" locale) is used.
  848. </P>
  849. <br><a name="SEC8" href="#TOC1">NEWLINES</a><br>
  850. <P>
  851. The <b>-N</b> (<b>--newline</b>) option allows <b>pcre2grep</b> to scan files with
  852. newline conventions that differ from the default. This option affects only the
  853. way scanned files are processed. It does not affect the interpretation of files
  854. specified by the <b>-f</b>, <b>--file-list</b>, <b>--exclude-from</b>, or
  855. <b>--include-from</b> options.
  856. </P>
  857. <P>
  858. Any parts of the scanned input files that are written to the standard output
  859. are copied with whatever newline sequences they have in the input. However, if
  860. the final line of a file is output, and it does not end with a newline
  861. sequence, a newline sequence is added. If the newline setting is CR, LF, CRLF
  862. or NUL, that line ending is output; for the other settings (ANYCRLF or ANY) a
  863. single NL is used.
  864. </P>
  865. <P>
  866. The newline setting does not affect the way in which <b>pcre2grep</b> writes
  867. newlines in informational messages to the standard output and error streams.
  868. Under Windows, the standard output is set to be binary, so that "\r\n" at the
  869. ends of output lines that are copied from the input is not converted to
  870. "\r\r\n" by the C I/O library. This means that any messages written to the
  871. standard output must end with "\r\n". For all other operating systems, and
  872. for all messages to the standard error stream, "\n" is used.
  873. </P>
  874. <br><a name="SEC9" href="#TOC1">OPTIONS COMPATIBILITY</a><br>
  875. <P>
  876. Many of the short and long forms of <b>pcre2grep</b>'s options are the same
  877. as in the GNU <b>grep</b> program. Any long option of the form
  878. <b>--xxx-regexp</b> (GNU terminology) is also available as <b>--xxx-regex</b>
  879. (PCRE2 terminology). However, the <b>--depth-limit</b>, <b>--file-list</b>,
  880. <b>--file-offsets</b>, <b>--heap-limit</b>, <b>--include-dir</b>,
  881. <b>--line-offsets</b>, <b>--locale</b>, <b>--match-limit</b>, <b>-M</b>,
  882. <b>--multiline</b>, <b>-N</b>, <b>--newline</b>, <b>--om-separator</b>,
  883. <b>--output</b>, <b>-u</b>, <b>--utf</b>, <b>-U</b>, and <b>--utf-allow-invalid</b>
  884. options are specific to <b>pcre2grep</b>, as is the use of the
  885. <b>--only-matching</b> option with a capturing parentheses number.
  886. </P>
  887. <P>
  888. Although most of the common options work the same way, a few are different in
  889. <b>pcre2grep</b>. For example, the <b>--include</b> option's argument is a glob
  890. for GNU <b>grep</b>, but a regular expression for <b>pcre2grep</b>. If both the
  891. <b>-c</b> and <b>-l</b> options are given, GNU grep lists only file names,
  892. without counts, but <b>pcre2grep</b> gives the counts as well.
  893. </P>
  894. <br><a name="SEC10" href="#TOC1">OPTIONS WITH DATA</a><br>
  895. <P>
  896. There are four different ways in which an option with data can be specified.
  897. If a short form option is used, the data may follow immediately, or (with one
  898. exception) in the next command line item. For example:
  899. <pre>
  900. -f/some/file
  901. -f /some/file
  902. </pre>
  903. The exception is the <b>-o</b> option, which may appear with or without data.
  904. Because of this, if data is present, it must follow immediately in the same
  905. item, for example -o3.
  906. </P>
  907. <P>
  908. If a long form option is used, the data may appear in the same command line
  909. item, separated by an equals character, or (with two exceptions) it may appear
  910. in the next command line item. For example:
  911. <pre>
  912. --file=/some/file
  913. --file /some/file
  914. </pre>
  915. Note, however, that if you want to supply a file name beginning with ~ as data
  916. in a shell command, and have the shell expand ~ to a home directory, you must
  917. separate the file name from the option, because the shell does not treat ~
  918. specially unless it is at the start of an item.
  919. </P>
  920. <P>
  921. The exceptions to the above are the <b>--colour</b> (or <b>--color</b>) and
  922. <b>--only-matching</b> options, for which the data is optional. If one of these
  923. options does have data, it must be given in the first form, using an equals
  924. character. Otherwise <b>pcre2grep</b> will assume that it has no data.
  925. </P>
  926. <br><a name="SEC11" href="#TOC1">USING PCRE2'S CALLOUT FACILITY</a><br>
  927. <P>
  928. <b>pcre2grep</b> has, by default, support for calling external programs or
  929. scripts or echoing specific strings during matching by making use of PCRE2's
  930. callout facility. However, this support can be completely or partially disabled
  931. when <b>pcre2grep</b> is built. You can find out whether your binary has support
  932. for callouts by running it with the <b>--help</b> option. If callout support is
  933. completely disabled, all callouts in patterns are ignored by <b>pcre2grep</b>.
  934. If the facility is partially disabled, calling external programs is not
  935. supported, and callouts that request it are ignored.
  936. </P>
  937. <P>
  938. A callout in a PCRE2 pattern is of the form (?C&#60;arg&#62;) where the argument is
  939. either a number or a quoted string (see the
  940. <a href="pcre2callout.html"><b>pcre2callout</b></a>
  941. documentation for details). Numbered callouts are ignored by <b>pcre2grep</b>;
  942. only callouts with string arguments are useful.
  943. </P>
  944. <br><b>
  945. Echoing a specific string
  946. </b><br>
  947. <P>
  948. Starting the callout string with a pipe character invokes an echoing facility
  949. that avoids calling an external program or script. This facility is always
  950. available, provided that callouts were not completely disabled when
  951. <b>pcre2grep</b> was built. The rest of the callout string is processed as a
  952. zero-terminated string, which means it should not contain any internal binary
  953. zeros. It is written to the output, having first been passed through the same
  954. escape processing as text from the <b>--output</b> (<b>-O</b>) option (see
  955. above). However, $0 cannot be used to insert a matched substring because the
  956. match is still in progress. Instead, the single character '0' is inserted. Any
  957. syntax errors in the string (for example, a dollar not followed by another
  958. character) causes the callout to be ignored. No terminator is added to the
  959. output string, so if you want a newline, you must include it explicitly using
  960. the escape $n. For example:
  961. <pre>
  962. pcre2grep '(.)(..(.))(?C"|[$1] [$2] [$3]$n")' &#60;some file&#62;
  963. </pre>
  964. Matching continues normally after the string is output. If you want to see only
  965. the callout output but not any output from an actual match, you should end the
  966. pattern with (*FAIL).
  967. </P>
  968. <br><b>
  969. Calling external programs or scripts
  970. </b><br>
  971. <P>
  972. This facility can be independently disabled when <b>pcre2grep</b> is built. It
  973. is supported for Windows, where a call to <b>_spawnvp()</b> is used, for VMS,
  974. where <b>lib$spawn()</b> is used, and for any Unix-like environment where
  975. <b>fork()</b> and <b>execv()</b> are available.
  976. </P>
  977. <P>
  978. If the callout string does not start with a pipe (vertical bar) character, it
  979. is parsed into a list of substrings separated by pipe characters. The first
  980. substring must be an executable name, with the following substrings specifying
  981. arguments:
  982. <pre>
  983. executable_name|arg1|arg2|...
  984. </pre>
  985. Any substring (including the executable name) may contain escape sequences
  986. started by a dollar character. These are the same as for the <b>--output</b>
  987. (<b>-O</b>) option documented above, except that $0 cannot insert the matched
  988. string because the match is still in progress. Instead, the character '0'
  989. is inserted. If you need a literal dollar or pipe character in any
  990. substring, use $$ or $| respectively. Here is an example:
  991. <pre>
  992. echo -e "abcde\n12345" | pcre2grep \
  993. '(?x)(.)(..(.))
  994. (?C"/bin/echo|Arg1: [$1] [$2] [$3]|Arg2: $|${1}$| ($4)")()' -
  995. Output:
  996. Arg1: [a] [bcd] [d] Arg2: |a| ()
  997. abcde
  998. Arg1: [1] [234] [4] Arg2: |1| ()
  999. 12345
  1000. </pre>
  1001. The parameters for the system call that is used to run the program or script
  1002. are zero-terminated strings. This means that binary zero characters in the
  1003. callout argument will cause premature termination of their substrings, and
  1004. therefore should not be present. Any syntax errors in the string (for example,
  1005. a dollar not followed by another character) causes the callout to be ignored.
  1006. If running the program fails for any reason (including the non-existence of the
  1007. executable), a local matching failure occurs and the matcher backtracks in the
  1008. normal way.
  1009. </P>
  1010. <br><a name="SEC12" href="#TOC1">MATCHING ERRORS</a><br>
  1011. <P>
  1012. It is possible to supply a regular expression that takes a very long time to
  1013. fail to match certain lines. Such patterns normally involve nested indefinite
  1014. repeats, for example: (a+)*\d when matched against a line of a's with no final
  1015. digit. The PCRE2 matching function has a resource limit that causes it to abort
  1016. in these circumstances. If this happens, <b>pcre2grep</b> outputs an error
  1017. message and the line that caused the problem to the standard error stream. If
  1018. there are more than 20 such errors, <b>pcre2grep</b> gives up.
  1019. </P>
  1020. <P>
  1021. The <b>--match-limit</b> option of <b>pcre2grep</b> can be used to set the
  1022. overall resource limit. There are also other limits that affect the amount of
  1023. memory used during matching; see the discussion of <b>--heap-limit</b> and
  1024. <b>--depth-limit</b> above.
  1025. </P>
  1026. <br><a name="SEC13" href="#TOC1">DIAGNOSTICS</a><br>
  1027. <P>
  1028. Exit status is 0 if any matches were found, 1 if no matches were found, and 2
  1029. for syntax errors, overlong lines, non-existent or inaccessible files (even if
  1030. matches were found in other files) or too many matching errors. Using the
  1031. <b>-s</b> option to suppress error messages about inaccessible files does not
  1032. affect the return code.
  1033. </P>
  1034. <P>
  1035. When run under VMS, the return code is placed in the symbol PCRE2GREP_RC
  1036. because VMS does not distinguish between exit(0) and exit(1).
  1037. </P>
  1038. <br><a name="SEC14" href="#TOC1">SEE ALSO</a><br>
  1039. <P>
  1040. <b>pcre2pattern</b>(3), <b>pcre2syntax</b>(3), <b>pcre2callout</b>(3),
  1041. <b>pcre2unicode</b>(3).
  1042. </P>
  1043. <br><a name="SEC15" href="#TOC1">AUTHOR</a><br>
  1044. <P>
  1045. Philip Hazel
  1046. <br>
  1047. Retired from University Computing Service
  1048. <br>
  1049. Cambridge, England.
  1050. <br>
  1051. </P>
  1052. <br><a name="SEC16" href="#TOC1">REVISION</a><br>
  1053. <P>
  1054. Last updated: 31 August 2021
  1055. <br>
  1056. Copyright &copy; 1997-2021 University of Cambridge.
  1057. <br>
  1058. <p>
  1059. Return to the <a href="index.html">PCRE2 index page</a>.
  1060. </p>