1PCREGREP(1) PCREGREP(1) 2 3 4NAME 5 pcregrep - a grep with Perl-compatible regular expressions. 6 7 8SYNOPSIS 9 pcregrep [options] [long options] [pattern] [path1 path2 ...] 10 11 12DESCRIPTION 13 14 pcregrep searches files for character patterns, in the same way as 15 other grep commands do, but it uses the PCRE regular expression library 16 to support patterns that are compatible with the regular expressions of 17 Perl 5. See pcrepattern(3) for a full description of syntax and seman- 18 tics of the regular expressions that PCRE supports. 19 20 Patterns, whether supplied on the command line or in a separate file, 21 are given without delimiters. For example: 22 23 pcregrep Thursday /etc/motd 24 25 If you attempt to use delimiters (for example, by surrounding a pattern 26 with slashes, as is common in Perl scripts), they are interpreted as 27 part of the pattern. Quotes can of course be used to delimit patterns 28 on the command line because they are interpreted by the shell, and 29 indeed they are required if a pattern contains white space or shell 30 metacharacters. 31 32 The first argument that follows any option settings is treated as the 33 single pattern to be matched when neither -e nor -f is present. Con- 34 versely, when one or both of these options are used to specify pat- 35 terns, all arguments are treated as path names. At least one of -e, -f, 36 or an argument pattern must be provided. 37 38 If no files are specified, pcregrep reads the standard input. The stan- 39 dard input can also be referenced by a name consisting of a single 40 hyphen. For example: 41 42 pcregrep some-pattern /file1 - /file3 43 44 By default, each line that matches a pattern is copied to the standard 45 output, and if there is more than one file, the file name is output at 46 the start of each line, followed by a colon. However, there are options 47 that can change how pcregrep behaves. In particular, the -M option 48 makes it possible to search for patterns that span line boundaries. 49 What defines a line boundary is controlled by the -N (--newline) 50 option. 51 52 The amount of memory used for buffering files that are being scanned is 53 controlled by a parameter that can be set by the --buffer-size option. 54 The default value for this parameter is specified when pcregrep is 55 built, with the default default being 20K. A block of memory three 56 times this size is used (to allow for buffering "before" and "after" 57 lines). An error occurs if a line overflows the buffer. 58 59 Patterns are limited to 8K or BUFSIZ bytes, whichever is the greater. 60 BUFSIZ is defined in <stdio.h>. When there is more than one pattern 61 (specified by the use of -e and/or -f), each pattern is applied to each 62 line in the order in which they are defined, except that all the -e 63 patterns are tried before the -f patterns. 64 65 By default, as soon as one pattern matches (or fails to match when -v 66 is used), no further patterns are considered. However, if --colour (or 67 --color) is used to colour the matching substrings, or if --only-match- 68 ing, --file-offsets, or --line-offsets is used to output only the part 69 of the line that matched (either shown literally, or as an offset), 70 scanning resumes immediately following the match, so that further 71 matches on the same line can be found. If there are multiple patterns, 72 they are all tried on the remainder of the line, but patterns that fol- 73 low the one that matched are not tried on the earlier part of the line. 74 75 This is the same behaviour as GNU grep, but it does mean that the order 76 in which multiple patterns are specified can affect the output when one 77 of the above options is used. 78 79 Patterns that can match an empty string are accepted, but empty string 80 matches are never recognized. An example is the pattern 81 "(super)?(man)?", in which all components are optional. This pattern 82 finds all occurrences of both "super" and "man"; the output differs 83 from matching with "super|man" when only the matching substrings are 84 being shown. 85 86 If the LC_ALL or LC_CTYPE environment variable is set, pcregrep uses 87 the value to set a locale when calling the PCRE library. The --locale 88 option can be used to override this. 89 90 91SUPPORT FOR COMPRESSED FILES 92 93 It is possible to compile pcregrep so that it uses libz or libbz2 to 94 read files whose names end in .gz or .bz2, respectively. You can find 95 out whether your binary has support for one or both of these file types 96 by running it with the --help option. If the appropriate support is not 97 present, files are treated as plain text. The standard input is always 98 so treated. 99 100 101BINARY FILES 102 103 By default, a file that contains a binary zero byte within the first 104 1024 bytes is identified as a binary file, and is processed specially. 105 (GNU grep also identifies binary files in this manner.) See the 106 --binary-files option for a means of changing the way binary files are 107 handled. 108 109 110OPTIONS 111 112 The order in which some of the options appear can affect the output. 113 For example, both the -h and -l options affect the printing of file 114 names. Whichever comes later in the command line will be the one that 115 takes effect. Numerical values for options may be followed by K or M, 116 to signify multiplication by 1024 or 1024*1024 respectively. 117 118 -- This terminates the list of options. It is useful if the next 119 item on the command line starts with a hyphen but is not an 120 option. This allows for the processing of patterns and file- 121 names that start with hyphens. 122 123 -A number, --after-context=number 124 Output number lines of context after each matching line. If 125 filenames and/or line numbers are being output, a hyphen sep- 126 arator is used instead of a colon for the context lines. A 127 line containing "--" is output between each group of lines, 128 unless they are in fact contiguous in the input file. The 129 value of number is expected to be relatively small. However, 130 pcregrep guarantees to have up to 8K of following text avail- 131 able for context output. 132 133 -a, --text 134 Treat binary files as text. This is equivalent to --binary- 135 files=text. 136 137 -B number, --before-context=number 138 Output number lines of context before each matching line. If 139 filenames and/or line numbers are being output, a hyphen sep- 140 arator is used instead of a colon for the context lines. A 141 line containing "--" is output between each group of lines, 142 unless they are in fact contiguous in the input file. The 143 value of number is expected to be relatively small. However, 144 pcregrep guarantees to have up to 8K of preceding text avail- 145 able for context output. 146 147 --binary-files=word 148 Specify how binary files are to be processed. If the word is 149 "binary" (the default), pattern matching is performed on 150 binary files, but the only output is "Binary file <name> 151 matches" when a match succeeds. If the word is "text", which 152 is equivalent to the -a or --text option, binary files are 153 processed in the same way as any other file. In this case, 154 when a match succeeds, the output may be binary garbage, 155 which can have nasty effects if sent to a terminal. If the 156 word is "without-match", which is equivalent to the -I 157 option, binary files are not processed at all; they are 158 assumed not to be of interest. 159 160 --buffer-size=number 161 Set the parameter that controls how much memory is used for 162 buffering files that are being scanned. 163 164 -C number, --context=number 165 Output number lines of context both before and after each 166 matching line. This is equivalent to setting both -A and -B 167 to the same value. 168 169 -c, --count 170 Do not output individual lines from the files that are being 171 scanned; instead output the number of lines that would other- 172 wise have been shown. If no lines are selected, the number 173 zero is output. If several files are are being scanned, a 174 count is output for each of them. However, if the --files- 175 with-matches option is also used, only those files whose 176 counts are greater than zero are listed. When -c is used, the 177 -A, -B, and -C options are ignored. 178 179 --colour, --color 180 If this option is given without any data, it is equivalent to 181 "--colour=auto". If data is required, it must be given in 182 the same shell item, separated by an equals sign. 183 184 --colour=value, --color=value 185 This option specifies under what circumstances the parts of a 186 line that matched a pattern should be coloured in the output. 187 By default, the output is not coloured. The value (which is 188 optional, see above) may be "never", "always", or "auto". In 189 the latter case, colouring happens only if the standard out- 190 put is connected to a terminal. More resources are used when 191 colouring is enabled, because pcregrep has to search for all 192 possible matches in a line, not just one, in order to colour 193 them all. 194 195 The colour that is used can be specified by setting the envi- 196 ronment variable PCREGREP_COLOUR or PCREGREP_COLOR. The value 197 of this variable should be a string of two numbers, separated 198 by a semicolon. They are copied directly into the control 199 string for setting colour on a terminal, so it is your 200 responsibility to ensure that they make sense. If neither of 201 the environment variables is set, the default is "1;31", 202 which gives red. 203 204 -D action, --devices=action 205 If an input path is not a regular file or a directory, 206 "action" specifies how it is to be processed. Valid values 207 are "read" (the default) or "skip" (silently skip the path). 208 209 -d action, --directories=action 210 If an input path is a directory, "action" specifies how it is 211 to be processed. Valid values are "read" (the default), 212 "recurse" (equivalent to the -r option), or "skip" (silently 213 skip the path). In the default case, directories are read as 214 if they were ordinary files. In some operating systems the 215 effect of reading a directory like this is an immediate end- 216 of-file. 217 218 -e pattern, --regex=pattern, --regexp=pattern 219 Specify a pattern to be matched. This option can be used mul- 220 tiple times in order to specify several patterns. It can also 221 be used as a way of specifying a single pattern that starts 222 with a hyphen. When -e is used, no argument pattern is taken 223 from the command line; all arguments are treated as file 224 names. There is an overall maximum of 100 patterns. They are 225 applied to each line in the order in which they are defined 226 until one matches (or fails to match if -v is used). If -f is 227 used with -e, the command line patterns are matched first, 228 followed by the patterns from the file, independent of the 229 order in which these options are specified. Note that multi- 230 ple use of -e is not the same as a single pattern with alter- 231 natives. For example, X|Y finds the first character in a line 232 that is X or Y, whereas if the two patterns are given sepa- 233 rately, pcregrep finds X if it is present, even if it follows 234 Y in the line. It finds Y only if there is no X in the line. 235 This really matters only if you are using -o to show the 236 part(s) of the line that matched. 237 238 --exclude=pattern 239 When pcregrep is searching the files in a directory as a con- 240 sequence of the -r (recursive search) option, any regular 241 files whose names match the pattern are excluded. Subdirecto- 242 ries are not excluded by this option; they are searched 243 recursively, subject to the --exclude-dir and --include_dir 244 options. The pattern is a PCRE regular expression, and is 245 matched against the final component of the file name (not the 246 entire path). If a file name matches both --include and 247 --exclude, it is excluded. There is no short form for this 248 option. 249 250 --exclude-dir=pattern 251 When pcregrep is searching the contents of a directory as a 252 consequence of the -r (recursive search) option, any subdi- 253 rectories whose names match the pattern are excluded. (Note 254 that the --exclude option does not affect subdirectories.) 255 The pattern is a PCRE regular expression, and is matched 256 against the final component of the name (not the entire 257 path). If a subdirectory name matches both --include-dir and 258 --exclude-dir, it is excluded. There is no short form for 259 this option. 260 261 -F, --fixed-strings 262 Interpret each pattern as a list of fixed strings, separated 263 by newlines, instead of as a regular expression. The -w 264 (match as a word) and -x (match whole line) options can be 265 used with -F. They apply to each of the fixed strings. A line 266 is selected if any of the fixed strings are found in it (sub- 267 ject to -w or -x, if present). 268 269 -f filename, --file=filename 270 Read a number of patterns from the file, one per line, and 271 match them against each line of input. A data line is output 272 if any of the patterns match it. The filename can be given as 273 "-" to refer to the standard input. When -f is used, patterns 274 specified on the command line using -e may also be present; 275 they are tested before the file's patterns. However, no other 276 pattern is taken from the command line; all arguments are 277 treated as the names of paths to be searched. There is an 278 overall maximum of 100 patterns. Trailing white space is 279 removed from each line, and blank lines are ignored. An empty 280 file contains no patterns and therefore matches nothing. See 281 also the comments about multiple patterns versus a single 282 pattern with alternatives in the description of -e above. 283 284 --file-list=filename 285 Read a list of files to be searched from the given file, one 286 per line. Trailing white space is removed from each line, and 287 blank lines are ignored. These files are searched before any 288 others that may be listed on the command line. The filename 289 can be given as "-" to refer to the standard input. If --file 290 and --file-list are both specified as "-", patterns are read 291 first. This is useful only when the standard input is a ter- 292 minal, from which further lines (the list of files) can be 293 read after an end-of-file indication. 294 295 --file-offsets 296 Instead of showing lines or parts of lines that match, show 297 each match as an offset from the start of the file and a 298 length, separated by a comma. In this mode, no context is 299 shown. That is, the -A, -B, and -C options are ignored. If 300 there is more than one match in a line, each of them is shown 301 separately. This option is mutually exclusive with --line- 302 offsets and --only-matching. 303 304 -H, --with-filename 305 Force the inclusion of the filename at the start of output 306 lines when searching a single file. By default, the filename 307 is not shown in this case. For matching lines, the filename 308 is followed by a colon; for context lines, a hyphen separator 309 is used. If a line number is also being output, it follows 310 the file name. 311 312 -h, --no-filename 313 Suppress the output filenames when searching multiple files. 314 By default, filenames are shown when multiple files are 315 searched. For matching lines, the filename is followed by a 316 colon; for context lines, a hyphen separator is used. If a 317 line number is also being output, it follows the file name. 318 319 --help Output a help message, giving brief details of the command 320 options and file type support, and then exit. 321 322 -I Treat binary files as never matching. This is equivalent to 323 --binary-files=without-match. 324 325 -i, --ignore-case 326 Ignore upper/lower case distinctions during comparisons. 327 328 --include=pattern 329 When pcregrep is searching the files in a directory as a con- 330 sequence of the -r (recursive search) option, only those reg- 331 ular files whose names match the pattern are included. Subdi- 332 rectories are always included and searched recursively, sub- 333 ject to the --include-dir and --exclude-dir options. The pat- 334 tern is a PCRE regular expression, and is matched against the 335 final component of the file name (not the entire path). If a 336 file name matches both --include and --exclude, it is 337 excluded. There is no short form for this option. 338 339 --include-dir=pattern 340 When pcregrep is searching the contents of a directory as a 341 consequence of the -r (recursive search) option, only those 342 subdirectories whose names match the pattern are included. 343 (Note that the --include option does not affect subdirecto- 344 ries.) The pattern is a PCRE regular expression, and is 345 matched against the final component of the name (not the 346 entire path). If a subdirectory name matches both --include- 347 dir and --exclude-dir, it is excluded. There is no short form 348 for this option. 349 350 -L, --files-without-match 351 Instead of outputting lines from the files, just output the 352 names of the files that do not contain any lines that would 353 have been output. Each file name is output once, on a sepa- 354 rate line. 355 356 -l, --files-with-matches 357 Instead of outputting lines from the files, just output the 358 names of the files containing lines that would have been out- 359 put. Each file name is output once, on a separate line. 360 Searching normally stops as soon as a matching line is found 361 in a file. However, if the -c (count) option is also used, 362 matching continues in order to obtain the correct count, and 363 those files that have at least one match are listed along 364 with their counts. Using this option with -c is a way of sup- 365 pressing the listing of files with no matches. 366 367 --label=name 368 This option supplies a name to be used for the standard input 369 when file names are being output. If not supplied, "(standard 370 input)" is used. There is no short form for this option. 371 372 --line-buffered 373 When this option is given, input is read and processed line 374 by line, and the output is flushed after each write. By 375 default, input is read in large chunks, unless pcregrep can 376 determine that it is reading from a terminal (which is cur- 377 rently possible only in Unix environments). Output to termi- 378 nal is normally automatically flushed by the operating sys- 379 tem. This option can be useful when the input or output is 380 attached to a pipe and you do not want pcregrep to buffer up 381 large amounts of data. However, its use will affect perfor- 382 mance, and the -M (multiline) option ceases to work. 383 384 --line-offsets 385 Instead of showing lines or parts of lines that match, show 386 each match as a line number, the offset from the start of the 387 line, and a length. The line number is terminated by a colon 388 (as usual; see the -n option), and the offset and length are 389 separated by a comma. In this mode, no context is shown. 390 That is, the -A, -B, and -C options are ignored. If there is 391 more than one match in a line, each of them is shown sepa- 392 rately. This option is mutually exclusive with --file-offsets 393 and --only-matching. 394 395 --locale=locale-name 396 This option specifies a locale to be used for pattern match- 397 ing. It overrides the value in the LC_ALL or LC_CTYPE envi- 398 ronment variables. If no locale is specified, the PCRE 399 library's default (usually the "C" locale) is used. There is 400 no short form for this option. 401 402 --match-limit=number 403 Processing some regular expression patterns can require a 404 very large amount of memory, leading in some cases to a pro- 405 gram crash if not enough is available. Other patterns may 406 take a very long time to search for all possible matching 407 strings. The pcre_exec() function that is called by pcregrep 408 to do the matching has two parameters that can limit the 409 resources that it uses. 410 411 The --match-limit option provides a means of limiting 412 resource usage when processing patterns that are not going to 413 match, but which have a very large number of possibilities in 414 their search trees. The classic example is a pattern that 415 uses nested unlimited repeats. Internally, PCRE uses a func- 416 tion called match() which it calls repeatedly (sometimes 417 recursively). The limit set by --match-limit is imposed on 418 the number of times this function is called during a match, 419 which has the effect of limiting the amount of backtracking 420 that can take place. 421 422 The --recursion-limit option is similar to --match-limit, but 423 instead of limiting the total number of times that match() is 424 called, it limits the depth of recursive calls, which in turn 425 limits the amount of memory that can be used. The recursion 426 depth is a smaller number than the total number of calls, 427 because not all calls to match() are recursive. This limit is 428 of use only if it is set smaller than --match-limit. 429 430 There are no short forms for these options. The default set- 431 tings are specified when the PCRE library is compiled, with 432 the default default being 10 million. 433 434 -M, --multiline 435 Allow patterns to match more than one line. When this option 436 is given, patterns may usefully contain literal newline char- 437 acters and internal occurrences of ^ and $ characters. The 438 output for a successful match may consist of more than one 439 line, the last of which is the one in which the match ended. 440 If the matched string ends with a newline sequence the output 441 ends at the end of that line. 442 443 When this option is set, the PCRE library is called in "mul- 444 tiline" mode. There is a limit to the number of lines that 445 can be matched, imposed by the way that pcregrep buffers the 446 input file as it scans it. However, pcregrep ensures that at 447 least 8K characters or the rest of the document (whichever is 448 the shorter) are available for forward matching, and simi- 449 larly the previous 8K characters (or all the previous charac- 450 ters, if fewer than 8K) are guaranteed to be available for 451 lookbehind assertions. This option does not work when input 452 is read line by line (see --line-buffered.) 453 454 -N newline-type, --newline=newline-type 455 The PCRE library supports five different conventions for 456 indicating the ends of lines. They are the single-character 457 sequences CR (carriage return) and LF (linefeed), the two- 458 character sequence CRLF, an "anycrlf" convention, which rec- 459 ognizes any of the preceding three types, and an "any" con- 460 vention, in which any Unicode line ending sequence is assumed 461 to end a line. The Unicode sequences are the three just men- 462 tioned, plus VT (vertical tab, U+000B), FF (form feed, 463 U+000C), NEL (next line, U+0085), LS (line separator, 464 U+2028), and PS (paragraph separator, U+2029). 465 466 When the PCRE library is built, a default line-ending 467 sequence is specified. This is normally the standard 468 sequence for the operating system. Unless otherwise specified 469 by this option, pcregrep uses the library's default. The 470 possible values for this option are CR, LF, CRLF, ANYCRLF, or 471 ANY. This makes it possible to use pcregrep on files that 472 have come from other environments without having to modify 473 their line endings. If the data that is being scanned does 474 not agree with the convention set by this option, pcregrep 475 may behave in strange ways. 476 477 -n, --line-number 478 Precede each output line by its line number in the file, fol- 479 lowed by a colon for matching lines or a hyphen for context 480 lines. If the filename is also being output, it precedes the 481 line number. This option is forced if --line-offsets is used. 482 483 --no-jit If the PCRE library is built with support for just-in-time 484 compiling (which speeds up matching), pcregrep automatically 485 makes use of this, unless it was explicitly disabled at build 486 time. This option can be used to disable the use of JIT at 487 run time. It is provided for testing and working round prob- 488 lems. It should never be needed in normal use. 489 490 -o, --only-matching 491 Show only the part of the line that matched a pattern instead 492 of the whole line. In this mode, no context is shown. That 493 is, the -A, -B, and -C options are ignored. If there is more 494 than one match in a line, each of them is shown separately. 495 If -o is combined with -v (invert the sense of the match to 496 find non-matching lines), no output is generated, but the 497 return code is set appropriately. If the matched portion of 498 the line is empty, nothing is output unless the file name or 499 line number are being printed, in which case they are shown 500 on an otherwise empty line. This option is mutually exclusive 501 with --file-offsets and --line-offsets. 502 503 -onumber, --only-matching=number 504 Show only the part of the line that matched the capturing 505 parentheses of the given number. Up to 32 capturing parenthe- 506 ses are supported. Because these options can be given without 507 an argument (see above), if an argument is present, it must 508 be given in the same shell item, for example, -o3 or --only- 509 matching=2. The comments given for the non-argument case 510 above also apply to this case. If the specified capturing 511 parentheses do not exist in the pattern, or were not set in 512 the match, nothing is output unless the file name or line 513 number are being printed. 514 515 -q, --quiet 516 Work quietly, that is, display nothing except error messages. 517 The exit status indicates whether or not any matches were 518 found. 519 520 -r, --recursive 521 If any given path is a directory, recursively scan the files 522 it contains, taking note of any --include and --exclude set- 523 tings. By default, a directory is read as a normal file; in 524 some operating systems this gives an immediate end-of-file. 525 This option is a shorthand for setting the -d option to 526 "recurse". 527 528 --recursion-limit=number 529 See --match-limit above. 530 531 -s, --no-messages 532 Suppress error messages about non-existent or unreadable 533 files. Such files are quietly skipped. However, the return 534 code is still 2, even if matches were found in other files. 535 536 -u, --utf-8 537 Operate in UTF-8 mode. This option is available only if PCRE 538 has been compiled with UTF-8 support. Both patterns and sub- 539 ject lines must be valid strings of UTF-8 characters. 540 541 -V, --version 542 Write the version numbers of pcregrep and the PCRE library 543 that is being used to the standard error stream. 544 545 -v, --invert-match 546 Invert the sense of the match, so that lines which do not 547 match any of the patterns are the ones that are found. 548 549 -w, --word-regex, --word-regexp 550 Force the patterns to match only whole words. This is equiva- 551 lent to having \b at the start and end of the pattern. 552 553 -x, --line-regex, --line-regexp 554 Force the patterns to be anchored (each must start matching 555 at the beginning of a line) and in addition, require them to 556 match entire lines. This is equivalent to having ^ and $ 557 characters at the start and end of each alternative branch in 558 every pattern. 559 560 561ENVIRONMENT VARIABLES 562 563 The environment variables LC_ALL and LC_CTYPE are examined, in that 564 order, for a locale. The first one that is set is used. This can be 565 overridden by the --locale option. If no locale is set, the PCRE 566 library's default (usually the "C" locale) is used. 567 568 569NEWLINES 570 571 The -N (--newline) option allows pcregrep to scan files with different 572 newline conventions from the default. However, the setting of this 573 option does not affect the way in which pcregrep writes information to 574 the standard error and output streams. It uses the string "\n" in C 575 printf() calls to indicate newlines, relying on the C I/O library to 576 convert this to an appropriate sequence if the output is sent to a 577 file. 578 579 580OPTIONS COMPATIBILITY 581 582 Many of the short and long forms of pcregrep's options are the same as 583 in the GNU grep program. Any long option of the form --xxx-regexp (GNU 584 terminology) is also available as --xxx-regex (PCRE terminology). How- 585 ever, the --file-list, --file-offsets, --include-dir, --line-offsets, 586 --locale, --match-limit, -M, --multiline, -N, --newline, --recursion- 587 limit, -u, and --utf-8 options are specific to pcregrep, as is the use 588 of the --only-matching option with a capturing parentheses number. 589 590 Although most of the common options work the same way, a few are dif- 591 ferent in pcregrep. For example, the --include option's argument is a 592 glob for GNU grep, but a regular expression for pcregrep. If both the 593 -c and -l options are given, GNU grep lists only file names, without 594 counts, but pcregrep gives the counts. 595 596 597OPTIONS WITH DATA 598 599 There are four different ways in which an option with data can be spec- 600 ified. If a short form option is used, the data may follow immedi- 601 ately, or (with one exception) in the next command line item. For exam- 602 ple: 603 604 -f/some/file 605 -f /some/file 606 607 The exception is the -o option, which may appear with or without data. 608 Because of this, if data is present, it must follow immediately in the 609 same item, for example -o3. 610 611 If a long form option is used, the data may appear in the same command 612 line item, separated by an equals character, or (with two exceptions) 613 it may appear in the next command line item. For example: 614 615 --file=/some/file 616 --file /some/file 617 618 Note, however, that if you want to supply a file name beginning with ~ 619 as data in a shell command, and have the shell expand ~ to a home 620 directory, you must separate the file name from the option, because the 621 shell does not treat ~ specially unless it is at the start of an item. 622 623 The exceptions to the above are the --colour (or --color) and --only- 624 matching options, for which the data is optional. If one of these 625 options does have data, it must be given in the first form, using an 626 equals character. Otherwise pcregrep will assume that it has no data. 627 628 629MATCHING ERRORS 630 631 It is possible to supply a regular expression that takes a very long 632 time to fail to match certain lines. Such patterns normally involve 633 nested indefinite repeats, for example: (a+)*\d when matched against a 634 line of a's with no final digit. The PCRE matching function has a 635 resource limit that causes it to abort in these circumstances. If this 636 happens, pcregrep outputs an error message and the line that caused the 637 problem to the standard error stream. If there are more than 20 such 638 errors, pcregrep gives up. 639 640 The --match-limit option of pcregrep can be used to set the overall 641 resource limit; there is a second option called --recursion-limit that 642 sets a limit on the amount of memory (usually stack) that is used (see 643 the discussion of these options above). 644 645 646DIAGNOSTICS 647 648 Exit status is 0 if any matches were found, 1 if no matches were found, 649 and 2 for syntax errors, overlong lines, non-existent or inaccessible 650 files (even if matches were found in other files) or too many matching 651 errors. Using the -s option to suppress error messages about inaccessi- 652 ble files does not affect the return code. 653 654 655SEE ALSO 656 657 pcrepattern(3), pcretest(1). 658 659 660AUTHOR 661 662 Philip Hazel 663 University Computing Service 664 Cambridge CB2 3QH, England. 665 666 667REVISION 668 669 Last updated: 04 March 2012 670 Copyright (c) 1997-2012 University of Cambridge. 671