1 PCREGREP(1) PCREGREP(1) 2 3 4 NAME 5 pcregrep - a grep with Perl-compatible regular expressions. 6 7 8 SYNOPSIS 9 pcregrep [options] [long options] [pattern] [path1 path2 ...] 10 11 12 DESCRIPTION 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 Patterns are limited to 8K or BUFSIZ characters, whichever is the 53 greater. BUFSIZ is defined in <stdio.h>. When there is more than one 54 pattern (specified by the use of -e and/or -f), each pattern is applied 55 to each line in the order in which they are defined, except that all 56 the -e patterns are tried before the -f patterns. 57 58 By default, as soon as one pattern matches (or fails to match when -v 59 is used), no further patterns are considered. However, if --colour (or 60 --color) is used to colour the matching substrings, or if --only-match- 61 ing, --file-offsets, or --line-offsets is used to output only the part 62 of the line that matched (either shown literally, or as an offset), 63 scanning resumes immediately following the match, so that further 64 matches on the same line can be found. If there are multiple patterns, 65 they are all tried on the remainder of the line, but patterns that fol- 66 low the one that matched are not tried on the earlier part of the line. 67 68 This is the same behaviour as GNU grep, but it does mean that the order 69 in which multiple patterns are specified can affect the output when one 70 of the above options is used. 71 72 Patterns that can match an empty string are accepted, but empty string 73 matches are never recognized. An example is the pattern 74 "(super)?(man)?", in which all components are optional. This pattern 75 finds all occurrences of both "super" and "man"; the output differs 76 from matching with "super|man" when only the matching substrings are 77 being shown. 78 79 If the LC_ALL or LC_CTYPE environment variable is set, pcregrep uses 80 the value to set a locale when calling the PCRE library. The --locale 81 option can be used to override this. 82 83 84 SUPPORT FOR COMPRESSED FILES 85 86 It is possible to compile pcregrep so that it uses libz or libbz2 to 87 read files whose names end in .gz or .bz2, respectively. You can find 88 out whether your binary has support for one or both of these file types 89 by running it with the --help option. If the appropriate support is not 90 present, files are treated as plain text. The standard input is always 91 so treated. 92 93 94 OPTIONS 95 96 The order in which some of the options appear can affect the output. 97 For example, both the -h and -l options affect the printing of file 98 names. Whichever comes later in the command line will be the one that 99 takes effect. 100 101 -- This terminate the list of options. It is useful if the next 102 item on the command line starts with a hyphen but is not an 103 option. This allows for the processing of patterns and file- 104 names that start with hyphens. 105 106 -A number, --after-context=number 107 Output number lines of context after each matching line. If 108 filenames and/or line numbers are being output, a hyphen sep- 109 arator is used instead of a colon for the context lines. A 110 line containing "--" is output between each group of lines, 111 unless they are in fact contiguous in the input file. The 112 value of number is expected to be relatively small. However, 113 pcregrep guarantees to have up to 8K of following text avail- 114 able for context output. 115 116 -B number, --before-context=number 117 Output number lines of context before each matching line. If 118 filenames and/or line numbers are being output, a hyphen sep- 119 arator is used instead of a colon for the context lines. A 120 line containing "--" is output between each group of lines, 121 unless they are in fact contiguous in the input file. The 122 value of number is expected to be relatively small. However, 123 pcregrep guarantees to have up to 8K of preceding text avail- 124 able for context output. 125 126 -C number, --context=number 127 Output number lines of context both before and after each 128 matching line. This is equivalent to setting both -A and -B 129 to the same value. 130 131 -c, --count 132 Do not output individual lines from the files that are being 133 scanned; instead output the number of lines that would other- 134 wise have been shown. If no lines are selected, the number 135 zero is output. If several files are are being scanned, a 136 count is output for each of them. However, if the --files- 137 with-matches option is also used, only those files whose 138 counts are greater than zero are listed. When -c is used, the 139 -A, -B, and -C options are ignored. 140 141 --colour, --color 142 If this option is given without any data, it is equivalent to 143 "--colour=auto". If data is required, it must be given in 144 the same shell item, separated by an equals sign. 145 146 --colour=value, --color=value 147 This option specifies under what circumstances the parts of a 148 line that matched a pattern should be coloured in the output. 149 By default, the output is not coloured. The value (which is 150 optional, see above) may be "never", "always", or "auto". In 151 the latter case, colouring happens only if the standard out- 152 put is connected to a terminal. More resources are used when 153 colouring is enabled, because pcregrep has to search for all 154 possible matches in a line, not just one, in order to colour 155 them all. 156 157 The colour that is used can be specified by setting the envi- 158 ronment variable PCREGREP_COLOUR or PCREGREP_COLOR. The value 159 of this variable should be a string of two numbers, separated 160 by a semicolon. They are copied directly into the control 161 string for setting colour on a terminal, so it is your 162 responsibility to ensure that they make sense. If neither of 163 the environment variables is set, the default is "1;31", 164 which gives red. 165 166 -D action, --devices=action 167 If an input path is not a regular file or a directory, 168 "action" specifies how it is to be processed. Valid values 169 are "read" (the default) or "skip" (silently skip the path). 170 171 -d action, --directories=action 172 If an input path is a directory, "action" specifies how it is 173 to be processed. Valid values are "read" (the default), 174 "recurse" (equivalent to the -r option), or "skip" (silently 175 skip the path). In the default case, directories are read as 176 if they were ordinary files. In some operating systems the 177 effect of reading a directory like this is an immediate end- 178 of-file. 179 180 -e pattern, --regex=pattern, --regexp=pattern 181 Specify a pattern to be matched. This option can be used mul- 182 tiple times in order to specify several patterns. It can also 183 be used as a way of specifying a single pattern that starts 184 with a hyphen. When -e is used, no argument pattern is taken 185 from the command line; all arguments are treated as file 186 names. There is an overall maximum of 100 patterns. They are 187 applied to each line in the order in which they are defined 188 until one matches (or fails to match if -v is used). If -f is 189 used with -e, the command line patterns are matched first, 190 followed by the patterns from the file, independent of the 191 order in which these options are specified. Note that multi- 192 ple use of -e is not the same as a single pattern with alter- 193 natives. For example, X|Y finds the first character in a line 194 that is X or Y, whereas if the two patterns are given sepa- 195 rately, pcregrep finds X if it is present, even if it follows 196 Y in the line. It finds Y only if there is no X in the line. 197 This really matters only if you are using -o to show the 198 part(s) of the line that matched. 199 200 --exclude=pattern 201 When pcregrep is searching the files in a directory as a con- 202 sequence of the -r (recursive search) option, any regular 203 files whose names match the pattern are excluded. Subdirecto- 204 ries are not excluded by this option; they are searched 205 recursively, subject to the --exclude-dir and --include_dir 206 options. The pattern is a PCRE regular expression, and is 207 matched against the final component of the file name (not the 208 entire path). If a file name matches both --include and 209 --exclude, it is excluded. There is no short form for this 210 option. 211 212 --exclude-dir=pattern 213 When pcregrep is searching the contents of a directory as a 214 consequence of the -r (recursive search) option, any subdi- 215 rectories whose names match the pattern are excluded. (Note 216 that the --exclude option does not affect subdirectories.) 217 The pattern is a PCRE regular expression, and is matched 218 against the final component of the name (not the entire 219 path). If a subdirectory name matches both --include-dir and 220 --exclude-dir, it is excluded. There is no short form for 221 this option. 222 223 -F, --fixed-strings 224 Interpret each pattern as a list of fixed strings, separated 225 by newlines, instead of as a regular expression. The -w 226 (match as a word) and -x (match whole line) options can be 227 used with -F. They apply to each of the fixed strings. A line 228 is selected if any of the fixed strings are found in it (sub- 229 ject to -w or -x, if present). 230 231 -f filename, --file=filename 232 Read a number of patterns from the file, one per line, and 233 match them against each line of input. A data line is output 234 if any of the patterns match it. The filename can be given as 235 "-" to refer to the standard input. When -f is used, patterns 236 specified on the command line using -e may also be present; 237 they are tested before the file's patterns. However, no other 238 pattern is taken from the command line; all arguments are 239 treated as file names. There is an overall maximum of 100 240 patterns. Trailing white space is removed from each line, and 241 blank lines are ignored. An empty file contains no patterns 242 and therefore matches nothing. See also the comments about 243 multiple patterns versus a single pattern with alternatives 244 in the description of -e above. 245 246 --file-offsets 247 Instead of showing lines or parts of lines that match, show 248 each match as an offset from the start of the file and a 249 length, separated by a comma. In this mode, no context is 250 shown. That is, the -A, -B, and -C options are ignored. If 251 there is more than one match in a line, each of them is shown 252 separately. This option is mutually exclusive with --line- 253 offsets and --only-matching. 254 255 -H, --with-filename 256 Force the inclusion of the filename at the start of output 257 lines when searching a single file. By default, the filename 258 is not shown in this case. For matching lines, the filename 259 is followed by a colon; for context lines, a hyphen separator 260 is used. If a line number is also being output, it follows 261 the file name. 262 263 -h, --no-filename 264 Suppress the output filenames when searching multiple files. 265 By default, filenames are shown when multiple files are 266 searched. For matching lines, the filename is followed by a 267 colon; for context lines, a hyphen separator is used. If a 268 line number is also being output, it follows the file name. 269 270 --help Output a help message, giving brief details of the command 271 options and file type support, and then exit. 272 273 -i, --ignore-case 274 Ignore upper/lower case distinctions during comparisons. 275 276 --include=pattern 277 When pcregrep is searching the files in a directory as a con- 278 sequence of the -r (recursive search) option, only those reg- 279 ular files whose names match the pattern are included. Subdi- 280 rectories are always included and searched recursively, sub- 281 ject to the --include-dir and --exclude-dir options. The pat- 282 tern is a PCRE regular expression, and is matched against the 283 final component of the file name (not the entire path). If a 284 file name matches both --include and --exclude, it is 285 excluded. There is no short form for this option. 286 287 --include-dir=pattern 288 When pcregrep is searching the contents of a directory as a 289 consequence of the -r (recursive search) option, only those 290 subdirectories whose names match the pattern are included. 291 (Note that the --include option does not affect subdirecto- 292 ries.) The pattern is a PCRE regular expression, and is 293 matched against the final component of the name (not the 294 entire path). If a subdirectory name matches both --include- 295 dir and --exclude-dir, it is excluded. There is no short form 296 for this option. 297 298 -L, --files-without-match 299 Instead of outputting lines from the files, just output the 300 names of the files that do not contain any lines that would 301 have been output. Each file name is output once, on a sepa- 302 rate line. 303 304 -l, --files-with-matches 305 Instead of outputting lines from the files, just output the 306 names of the files containing lines that would have been out- 307 put. Each file name is output once, on a separate line. 308 Searching normally stops as soon as a matching line is found 309 in a file. However, if the -c (count) option is also used, 310 matching continues in order to obtain the correct count, and 311 those files that have at least one match are listed along 312 with their counts. Using this option with -c is a way of sup- 313 pressing the listing of files with no matches. 314 315 --label=name 316 This option supplies a name to be used for the standard input 317 when file names are being output. If not supplied, "(standard 318 input)" is used. There is no short form for this option. 319 320 --line-buffered 321 When this option is given, input is read and processed line 322 by line, and the output is flushed after each write. By 323 default, input is read in large chunks, unless pcregrep can 324 determine that it is reading from a terminal (which is cur- 325 rently possible only in Unix environments). Output to termi- 326 nal is normally automatically flushed by the operating sys- 327 tem. This option can be useful when the input or output is 328 attached to a pipe and you do not want pcregrep to buffer up 329 large amounts of data. However, its use will affect perfor- 330 mance, and the -M (multiline) option ceases to work. 331 332 --line-offsets 333 Instead of showing lines or parts of lines that match, show 334 each match as a line number, the offset from the start of the 335 line, and a length. The line number is terminated by a colon 336 (as usual; see the -n option), and the offset and length are 337 separated by a comma. In this mode, no context is shown. 338 That is, the -A, -B, and -C options are ignored. If there is 339 more than one match in a line, each of them is shown sepa- 340 rately. This option is mutually exclusive with --file-offsets 341 and --only-matching. 342 343 --locale=locale-name 344 This option specifies a locale to be used for pattern match- 345 ing. It overrides the value in the LC_ALL or LC_CTYPE envi- 346 ronment variables. If no locale is specified, the PCRE 347 library's default (usually the "C" locale) is used. There is 348 no short form for this option. 349 350 --match-limit=number 351 Processing some regular expression patterns can require a 352 very large amount of memory, leading in some cases to a pro- 353 gram crash if not enough is available. Other patterns may 354 take a very long time to search for all possible matching 355 strings. The pcre_exec() function that is called by pcregrep 356 to do the matching has two parameters that can limit the 357 resources that it uses. 358 359 The --match-limit option provides a means of limiting 360 resource usage when processing patterns that are not going to 361 match, but which have a very large number of possibilities in 362 their search trees. The classic example is a pattern that 363 uses nested unlimited repeats. Internally, PCRE uses a func- 364 tion called match() which it calls repeatedly (sometimes 365 recursively). The limit set by --match-limit is imposed on 366 the number of times this function is called during a match, 367 which has the effect of limiting the amount of backtracking 368 that can take place. 369 370 The --recursion-limit option is similar to --match-limit, but 371 instead of limiting the total number of times that match() is 372 called, it limits the depth of recursive calls, which in turn 373 limits the amount of memory that can be used. The recursion 374 depth is a smaller number than the total number of calls, 375 because not all calls to match() are recursive. This limit is 376 of use only if it is set smaller than --match-limit. 377 378 There are no short forms for these options. The default set- 379 tings are specified when the PCRE library is compiled, with 380 the default default being 10 million. 381 382 -M, --multiline 383 Allow patterns to match more than one line. When this option 384 is given, patterns may usefully contain literal newline char- 385 acters and internal occurrences of ^ and $ characters. The 386 output for a successful match may consist of more than one 387 line, the last of which is the one in which the match ended. 388 If the matched string ends with a newline sequence the output 389 ends at the end of that line. 390 391 When this option is set, the PCRE library is called in "mul- 392 tiline" mode. There is a limit to the number of lines that 393 can be matched, imposed by the way that pcregrep buffers the 394 input file as it scans it. However, pcregrep ensures that at 395 least 8K characters or the rest of the document (whichever is 396 the shorter) are available for forward matching, and simi- 397 larly the previous 8K characters (or all the previous charac- 398 ters, if fewer than 8K) are guaranteed to be available for 399 lookbehind assertions. This option does not work when input 400 is read line by line (see --line-buffered.) 401 402 -N newline-type, --newline=newline-type 403 The PCRE library supports five different conventions for 404 indicating the ends of lines. They are the single-character 405 sequences CR (carriage return) and LF (linefeed), the two- 406 character sequence CRLF, an "anycrlf" convention, which rec- 407 ognizes any of the preceding three types, and an "any" con- 408 vention, in which any Unicode line ending sequence is assumed 409 to end a line. The Unicode sequences are the three just men- 410 tioned, plus VT (vertical tab, U+000B), FF (formfeed, 411 U+000C), NEL (next line, U+0085), LS (line separator, 412 U+2028), and PS (paragraph separator, U+2029). 413 414 When the PCRE library is built, a default line-ending 415 sequence is specified. This is normally the standard 416 sequence for the operating system. Unless otherwise specified 417 by this option, pcregrep uses the library's default. The 418 possible values for this option are CR, LF, CRLF, ANYCRLF, or 419 ANY. This makes it possible to use pcregrep on files that 420 have come from other environments without having to modify 421 their line endings. If the data that is being scanned does 422 not agree with the convention set by this option, pcregrep 423 may behave in strange ways. 424 425 -n, --line-number 426 Precede each output line by its line number in the file, fol- 427 lowed by a colon for matching lines or a hyphen for context 428 lines. If the filename is also being output, it precedes the 429 line number. This option is forced if --line-offsets is used. 430 431 -o, --only-matching 432 Show only the part of the line that matched a pattern instead 433 of the whole line. In this mode, no context is shown. That 434 is, the -A, -B, and -C options are ignored. If there is more 435 than one match in a line, each of them is shown separately. 436 If -o is combined with -v (invert the sense of the match to 437 find non-matching lines), no output is generated, but the 438 return code is set appropriately. If the matched portion of 439 the line is empty, nothing is output unless the file name or 440 line number are being printed, in which case they are shown 441 on an otherwise empty line. This option is mutually exclusive 442 with --file-offsets and --line-offsets. 443 444 -onumber, --only-matching=number 445 Show only the part of the line that matched the capturing 446 parentheses of the given number. Up to 32 capturing parenthe- 447 ses are supported. Because these options can be given without 448 an argument (see above), if an argument is present, it must 449 be given in the same shell item, for example, -o3 or --only- 450 matching=2. The comments given for the non-argument case 451 above also apply to this case. If the specified capturing 452 parentheses do not exist in the pattern, or were not set in 453 the match, nothing is output unless the file name or line 454 number are being printed. 455 456 -q, --quiet 457 Work quietly, that is, display nothing except error messages. 458 The exit status indicates whether or not any matches were 459 found. 460 461 -r, --recursive 462 If any given path is a directory, recursively scan the files 463 it contains, taking note of any --include and --exclude set- 464 tings. By default, a directory is read as a normal file; in 465 some operating systems this gives an immediate end-of-file. 466 This option is a shorthand for setting the -d option to 467 "recurse". 468 469 --recursion-limit=number 470 See --match-limit above. 471 472 -s, --no-messages 473 Suppress error messages about non-existent or unreadable 474 files. Such files are quietly skipped. However, the return 475 code is still 2, even if matches were found in other files. 476 477 -u, --utf-8 478 Operate in UTF-8 mode. This option is available only if PCRE 479 has been compiled with UTF-8 support. Both patterns and sub- 480 ject lines must be valid strings of UTF-8 characters. 481 482 -V, --version 483 Write the version numbers of pcregrep and the PCRE library 484 that is being used to the standard error stream. 485 486 -v, --invert-match 487 Invert the sense of the match, so that lines which do not 488 match any of the patterns are the ones that are found. 489 490 -w, --word-regex, --word-regexp 491 Force the patterns to match only whole words. This is equiva- 492 lent to having \b at the start and end of the pattern. 493 494 -x, --line-regex, --line-regexp 495 Force the patterns to be anchored (each must start matching 496 at the beginning of a line) and in addition, require them to 497 match entire lines. This is equivalent to having ^ and $ 498 characters at the start and end of each alternative branch in 499 every pattern. 500 501 502 ENVIRONMENT VARIABLES 503 504 The environment variables LC_ALL and LC_CTYPE are examined, in that 505 order, for a locale. The first one that is set is used. This can be 506 overridden by the --locale option. If no locale is set, the PCRE 507 library's default (usually the "C" locale) is used. 508 509 510 NEWLINES 511 512 The -N (--newline) option allows pcregrep to scan files with different 513 newline conventions from the default. However, the setting of this 514 option does not affect the way in which pcregrep writes information to 515 the standard error and output streams. It uses the string "\n" in C 516 printf() calls to indicate newlines, relying on the C I/O library to 517 convert this to an appropriate sequence if the output is sent to a 518 file. 519 520 521 OPTIONS COMPATIBILITY 522 523 Many of the short and long forms of pcregrep's options are the same as 524 in the GNU grep program (version 2.5.4). Any long option of the form 525 --xxx-regexp (GNU terminology) is also available as --xxx-regex (PCRE 526 terminology). However, the --file-offsets, --include-dir, --line-off- 527 sets, --locale, --match-limit, -M, --multiline, -N, --newline, --recur- 528 sion-limit, -u, and --utf-8 options are specific to pcregrep, as is the 529 use of the --only-matching option with a capturing parentheses number. 530 531 Although most of the common options work the same way, a few are dif- 532 ferent in pcregrep. For example, the --include option's argument is a 533 glob for GNU grep, but a regular expression for pcregrep. If both the 534 -c and -l options are given, GNU grep lists only file names, without 535 counts, but pcregrep gives the counts. 536 537 538 OPTIONS WITH DATA 539 540 There are four different ways in which an option with data can be spec- 541 ified. If a short form option is used, the data may follow immedi- 542 ately, or (with one exception) in the next command line item. For exam- 543 ple: 544 545 -f/some/file 546 -f /some/file 547 548 The exception is the -o option, which may appear with or without data. 549 Because of this, if data is present, it must follow immediately in the 550 same item, for example -o3. 551 552 If a long form option is used, the data may appear in the same command 553 line item, separated by an equals character, or (with two exceptions) 554 it may appear in the next command line item. For example: 555 556 --file=/some/file 557 --file /some/file 558 559 Note, however, that if you want to supply a file name beginning with ~ 560 as data in a shell command, and have the shell expand ~ to a home 561 directory, you must separate the file name from the option, because the 562 shell does not treat ~ specially unless it is at the start of an item. 563 564 The exceptions to the above are the --colour (or --color) and --only- 565 matching options, for which the data is optional. If one of these 566 options does have data, it must be given in the first form, using an 567 equals character. Otherwise pcregrep will assume that it has no data. 568 569 570 MATCHING ERRORS 571 572 It is possible to supply a regular expression that takes a very long 573 time to fail to match certain lines. Such patterns normally involve 574 nested indefinite repeats, for example: (a+)*\d when matched against a 575 line of a's with no final digit. The PCRE matching function has a 576 resource limit that causes it to abort in these circumstances. If this 577 happens, pcregrep outputs an error message and the line that caused the 578 problem to the standard error stream. If there are more than 20 such 579 errors, pcregrep gives up. 580 581 The --match-limit option of pcregrep can be used to set the overall 582 resource limit; there is a second option called --recursion-limit that 583 sets a limit on the amount of memory (usually stack) that is used (see 584 the discussion of these options above). 585 586 587 DIAGNOSTICS 588 589 Exit status is 0 if any matches were found, 1 if no matches were found, 590 and 2 for syntax errors and non-existent or inacessible files (even if 591 matches were found in other files) or too many matching errors. Using 592 the -s option to suppress error messages about inaccessble files does 593 not affect the return code. 594 595 596 SEE ALSO 597 598 pcrepattern(3), pcretest(1). 599 600 601 AUTHOR 602 603 Philip Hazel 604 University Computing Service 605 Cambridge CB2 3QH, England. 606 607 608 REVISION 609 610 Last updated: 14 January 2011 611 Copyright (c) 1997-2011 University of Cambridge. 612
