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1 PCRETEST(1) PCRETEST(1)
2
3
4 NAME
5 pcretest - a program for testing Perl-compatible regular expressions.
6
7
8 SYNOPSIS
9
10 pcretest [options] [input file [output file]]
11
12 pcretest was written as a test program for the PCRE regular expression
13 library itself, but it can also be used for experimenting with regular
14 expressions. This document describes the features of the test program;
15 for details of the regular expressions themselves, see the pcrepattern
16 documentation. For details of the PCRE library function calls and their
17 options, see the pcreapi documentation. The input for pcretest is a
18 sequence of regular expression patterns and strings to be matched, as
19 described below. The output shows the result of each match. Options on
20 the command line and the patterns control PCRE options and exactly what
21 is output.
22
23
24 COMMAND LINE OPTIONS
25
26 -b Behave as if each pattern has the /B (show byte code) modi-
27 fier; the internal form is output after compilation.
28
29 -C Output the version number of the PCRE library, and all avail-
30 able information about the optional features that are
31 included, and then exit.
32
33 -d Behave as if each pattern has the /D (debug) modifier; the
34 internal form and information about the compiled pattern is
35 output after compilation; -d is equivalent to -b -i.
36
37 -dfa Behave as if each data line contains the \D escape sequence;
38 this causes the alternative matching function,
39 pcre_dfa_exec(), to be used instead of the standard
40 pcre_exec() function (more detail is given below).
41
42 -help Output a brief summary these options and then exit.
43
44 -i Behave as if each pattern has the /I modifier; information
45 about the compiled pattern is given after compilation.
46
47 -M Behave as if each data line contains the \M escape sequence;
48 this causes PCRE to discover the minimum MATCH_LIMIT and
49 MATCH_LIMIT_RECURSION settings by calling pcre_exec() repeat-
50 edly with different limits.
51
52 -m Output the size of each compiled pattern after it has been
53 compiled. This is equivalent to adding /M to each regular
54 expression.
55
56 -o osize Set the number of elements in the output vector that is used
57 when calling pcre_exec() or pcre_dfa_exec() to be osize. The
58 default value is 45, which is enough for 14 capturing subex-
59 pressions for pcre_exec() or 22 different matches for
60 pcre_dfa_exec(). The vector size can be changed for individ-
61 ual matching calls by including \O in the data line (see
62 below).
63
64 -p Behave as if each pattern has the /P modifier; the POSIX
65 wrapper API is used to call PCRE. None of the other options
66 has any effect when -p is set.
67
68 -q Do not output the version number of pcretest at the start of
69 execution.
70
71 -S size On Unix-like systems, set the size of the run-time stack to
72 size megabytes.
73
74 -s Behave as if each pattern has the /S modifier; in other
75 words, force each pattern to be studied. If the /I or /D
76 option is present on a pattern (requesting output about the
77 compiled pattern), information about the result of studying
78 is not included when studying is caused only by -s and nei-
79 ther -i nor -d is present on the command line. This behaviour
80 means that the output from tests that are run with and with-
81 out -s should be identical, except when options that output
82 information about the actual running of a match are set. The
83 -M, -t, and -tm options, which give information about
84 resources used, are likely to produce different output with
85 and without -s. Output may also differ if the /C option is
86 present on an individual pattern. This uses callouts to trace
87 the the matching process, and this may be different between
88 studied and non-studied patterns. If the pattern contains
89 (*MARK) items there may also be differences, for the same
90 reason. The -s command line option can be overridden for spe-
91 cific patterns that should never be studied (see the /S
92 option below).
93
94 -t Run each compile, study, and match many times with a timer,
95 and output resulting time per compile or match (in millisec-
96 onds). Do not set -m with -t, because you will then get the
97 size output a zillion times, and the timing will be dis-
98 torted. You can control the number of iterations that are
99 used for timing by following -t with a number (as a separate
100 item on the command line). For example, "-t 1000" would iter-
101 ate 1000 times. The default is to iterate 500000 times.
102
103 -tm This is like -t except that it times only the matching phase,
104 not the compile or study phases.
105
106
107 DESCRIPTION
108
109 If pcretest is given two filename arguments, it reads from the first
110 and writes to the second. If it is given only one filename argument, it
111 reads from that file and writes to stdout. Otherwise, it reads from
112 stdin and writes to stdout, and prompts for each line of input, using
113 "re>" to prompt for regular expressions, and "data>" to prompt for data
114 lines.
115
116 When pcretest is built, a configuration option can specify that it
117 should be linked with the libreadline library. When this is done, if
118 the input is from a terminal, it is read using the readline() function.
119 This provides line-editing and history facilities. The output from the
120 -help option states whether or not readline() will be used.
121
122 The program handles any number of sets of input on a single input file.
123 Each set starts with a regular expression, and continues with any num-
124 ber of data lines to be matched against the pattern.
125
126 Each data line is matched separately and independently. If you want to
127 do multi-line matches, you have to use the \n escape sequence (or \r or
128 \r\n, etc., depending on the newline setting) in a single line of input
129 to encode the newline sequences. There is no limit on the length of
130 data lines; the input buffer is automatically extended if it is too
131 small.
132
133 An empty line signals the end of the data lines, at which point a new
134 regular expression is read. The regular expressions are given enclosed
135 in any non-alphanumeric delimiters other than backslash, for example:
136
137 /(a|bc)x+yz/
138
139 White space before the initial delimiter is ignored. A regular expres-
140 sion may be continued over several input lines, in which case the new-
141 line characters are included within it. It is possible to include the
142 delimiter within the pattern by escaping it, for example
143
144 /abc\/def/
145
146 If you do so, the escape and the delimiter form part of the pattern,
147 but since delimiters are always non-alphanumeric, this does not affect
148 its interpretation. If the terminating delimiter is immediately fol-
149 lowed by a backslash, for example,
150
151 /abc/\
152
153 then a backslash is added to the end of the pattern. This is done to
154 provide a way of testing the error condition that arises if a pattern
155 finishes with a backslash, because
156
157 /abc\/
158
159 is interpreted as the first line of a pattern that starts with "abc/",
160 causing pcretest to read the next line as a continuation of the regular
161 expression.
162
163
164 PATTERN MODIFIERS
165
166 A pattern may be followed by any number of modifiers, which are mostly
167 single characters. Following Perl usage, these are referred to below
168 as, for example, "the /i modifier", even though the delimiter of the
169 pattern need not always be a slash, and no slash is used when writing
170 modifiers. White space may appear between the final pattern delimiter
171 and the first modifier, and between the modifiers themselves.
172
173 The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
174 PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when pcre_com-
175 pile() is called. These four modifier letters have the same effect as
176 they do in Perl. For example:
177
178 /caseless/i
179
180 The following table shows additional modifiers for setting PCRE com-
181 pile-time options that do not correspond to anything in Perl:
182
183 /8 PCRE_UTF8
184 /? PCRE_NO_UTF8_CHECK
185 /A PCRE_ANCHORED
186 /C PCRE_AUTO_CALLOUT
187 /E PCRE_DOLLAR_ENDONLY
188 /f PCRE_FIRSTLINE
189 /J PCRE_DUPNAMES
190 /N PCRE_NO_AUTO_CAPTURE
191 /U PCRE_UNGREEDY
192 /W PCRE_UCP
193 /X PCRE_EXTRA
194 /Y PCRE_NO_START_OPTIMIZE
195 /<JS> PCRE_JAVASCRIPT_COMPAT
196 /<cr> PCRE_NEWLINE_CR
197 /<lf> PCRE_NEWLINE_LF
198 /<crlf> PCRE_NEWLINE_CRLF
199 /<anycrlf> PCRE_NEWLINE_ANYCRLF
200 /<any> PCRE_NEWLINE_ANY
201 /<bsr_anycrlf> PCRE_BSR_ANYCRLF
202 /<bsr_unicode> PCRE_BSR_UNICODE
203
204 The modifiers that are enclosed in angle brackets are literal strings
205 as shown, including the angle brackets, but the letters within can be
206 in either case. This example sets multiline matching with CRLF as the
207 line ending sequence:
208
209 /^abc/m<CRLF>
210
211 As well as turning on the PCRE_UTF8 option, the /8 modifier also causes
212 any non-printing characters in output strings to be printed using the
213 \x{hh...} notation if they are valid UTF-8 sequences. Full details of
214 the PCRE options are given in the pcreapi documentation.
215
216 Finding all matches in a string
217
218 Searching for all possible matches within each subject string can be
219 requested by the /g or /G modifier. After finding a match, PCRE is
220 called again to search the remainder of the subject string. The differ-
221 ence between /g and /G is that the former uses the startoffset argument
222 to pcre_exec() to start searching at a new point within the entire
223 string (which is in effect what Perl does), whereas the latter passes
224 over a shortened substring. This makes a difference to the matching
225 process if the pattern begins with a lookbehind assertion (including \b
226 or \B).
227
228 If any call to pcre_exec() in a /g or /G sequence matches an empty
229 string, the next call is done with the PCRE_NOTEMPTY_ATSTART and
230 PCRE_ANCHORED flags set in order to search for another, non-empty,
231 match at the same point. If this second match fails, the start offset
232 is advanced, and the normal match is retried. This imitates the way
233 Perl handles such cases when using the /g modifier or the split() func-
234 tion. Normally, the start offset is advanced by one character, but if
235 the newline convention recognizes CRLF as a newline, and the current
236 character is CR followed by LF, an advance of two is used.
237
238 Other modifiers
239
240 There are yet more modifiers for controlling the way pcretest operates.
241
242 The /+ modifier requests that as well as outputting the substring that
243 matched the entire pattern, pcretest should in addition output the
244 remainder of the subject string. This is useful for tests where the
245 subject contains multiple copies of the same substring. If the + modi-
246 fier appears twice, the same action is taken for captured substrings.
247 In each case the remainder is output on the following line with a plus
248 character following the capture number.
249
250 The /= modifier requests that the values of all potential captured
251 parentheses be output after a match by pcre_exec(). By default, only
252 those up to the highest one actually used in the match are output (cor-
253 responding to the return code from pcre_exec()). Values in the offsets
254 vector corresponding to higher numbers should be set to -1, and these
255 are output as "<unset>". This modifier gives a way of checking that
256 this is happening.
257
258 The /B modifier is a debugging feature. It requests that pcretest out-
259 put a representation of the compiled byte code after compilation. Nor-
260 mally this information contains length and offset values; however, if
261 /Z is also present, this data is replaced by spaces. This is a special
262 feature for use in the automatic test scripts; it ensures that the same
263 output is generated for different internal link sizes.
264
265 The /D modifier is a PCRE debugging feature, and is equivalent to /BI,
266 that is, both the /B and the /I modifiers.
267
268 The /F modifier causes pcretest to flip the byte order of the fields in
269 the compiled pattern that contain 2-byte and 4-byte numbers. This
270 facility is for testing the feature in PCRE that allows it to execute
271 patterns that were compiled on a host with a different endianness. This
272 feature is not available when the POSIX interface to PCRE is being
273 used, that is, when the /P pattern modifier is specified. See also the
274 section about saving and reloading compiled patterns below.
275
276 The /I modifier requests that pcretest output information about the
277 compiled pattern (whether it is anchored, has a fixed first character,
278 and so on). It does this by calling pcre_fullinfo() after compiling a
279 pattern. If the pattern is studied, the results of that are also out-
280 put.
281
282 The /K modifier requests pcretest to show names from backtracking con-
283 trol verbs that are returned from calls to pcre_exec(). It causes
284 pcretest to create a pcre_extra block if one has not already been cre-
285 ated by a call to pcre_study(), and to set the PCRE_EXTRA_MARK flag and
286 the mark field within it, every time that pcre_exec() is called. If the
287 variable that the mark field points to is non-NULL for a match, non-
288 match, or partial match, pcretest prints the string to which it points.
289 For a match, this is shown on a line by itself, tagged with "MK:". For
290 a non-match it is added to the message.
291
292 The /L modifier must be followed directly by the name of a locale, for
293 example,
294
295 /pattern/Lfr_FR
296
297 For this reason, it must be the last modifier. The given locale is set,
298 pcre_maketables() is called to build a set of character tables for the
299 locale, and this is then passed to pcre_compile() when compiling the
300 regular expression. Without an /L (or /T) modifier, NULL is passed as
301 the tables pointer; that is, /L applies only to the expression on which
302 it appears.
303
304 The /M modifier causes the size of memory block used to hold the com-
305 piled pattern to be output.
306
307 If the /S modifier appears once, it causes pcre_study() to be called
308 after the expression has been compiled, and the results used when the
309 expression is matched. If /S appears twice, it suppresses studying,
310 even if it was requested externally by the -s command line option. This
311 makes it possible to specify that certain patterns are always studied,
312 and others are never studied, independently of -s. This feature is used
313 in the test files in a few cases where the output is different when the
314 pattern is studied.
315
316 The /T modifier must be followed by a single digit. It causes a spe-
317 cific set of built-in character tables to be passed to pcre_compile().
318 It is used in the standard PCRE tests to check behaviour with different
319 character tables. The digit specifies the tables as follows:
320
321 0 the default ASCII tables, as distributed in
322 pcre_chartables.c.dist
323 1 a set of tables defining ISO 8859 characters
324
325 In table 1, some characters whose codes are greater than 128 are iden-
326 tified as letters, digits, spaces, etc.
327
328 Using the POSIX wrapper API
329
330 The /P modifier causes pcretest to call PCRE via the POSIX wrapper API
331 rather than its native API. When /P is set, the following modifiers set
332 options for the regcomp() function:
333
334 /i REG_ICASE
335 /m REG_NEWLINE
336 /N REG_NOSUB
337 /s REG_DOTALL )
338 /U REG_UNGREEDY ) These options are not part of
339 /W REG_UCP ) the POSIX standard
340 /8 REG_UTF8 )
341
342 The /+ modifier works as described above. All other modifiers are
343 ignored.
344
345
346 DATA LINES
347
348 Before each data line is passed to pcre_exec(), leading and trailing
349 white space is removed, and it is then scanned for \ escapes. Some of
350 these are pretty esoteric features, intended for checking out some of
351 the more complicated features of PCRE. If you are just testing "ordi-
352 nary" regular expressions, you probably don't need any of these. The
353 following escapes are recognized:
354
355 \a alarm (BEL, \x07)
356 \b backspace (\x08)
357 \e escape (\x27)
358 \f form feed (\x0c)
359 \n newline (\x0a)
360 \qdd set the PCRE_MATCH_LIMIT limit to dd
361 (any number of digits)
362 \r carriage return (\x0d)
363 \t tab (\x09)
364 \v vertical tab (\x0b)
365 \nnn octal character (up to 3 octal digits)
366 always a byte unless > 255 in UTF-8 mode
367 \xhh hexadecimal byte (up to 2 hex digits)
368 \x{hh...} hexadecimal character, any number of digits
369 in UTF-8 mode
370 \A pass the PCRE_ANCHORED option to pcre_exec()
371 or pcre_dfa_exec()
372 \B pass the PCRE_NOTBOL option to pcre_exec()
373 or pcre_dfa_exec()
374 \Cdd call pcre_copy_substring() for substring dd
375 after a successful match (number less than 32)
376 \Cname call pcre_copy_named_substring() for substring
377 "name" after a successful match (name termin-
378 ated by next non alphanumeric character)
379 \C+ show the current captured substrings at callout
380 time
381 \C- do not supply a callout function
382 \C!n return 1 instead of 0 when callout number n is
383 reached
384 \C!n!m return 1 instead of 0 when callout number n is
385 reached for the nth time
386 \C*n pass the number n (may be negative) as callout
387 data; this is used as the callout return value
388 \D use the pcre_dfa_exec() match function
389 \F only shortest match for pcre_dfa_exec()
390 \Gdd call pcre_get_substring() for substring dd
391 after a successful match (number less than 32)
392 \Gname call pcre_get_named_substring() for substring
393 "name" after a successful match (name termin-
394 ated by next non-alphanumeric character)
395 \L call pcre_get_substringlist() after a
396 successful match
397 \M discover the minimum MATCH_LIMIT and
398 MATCH_LIMIT_RECURSION settings
399 \N pass the PCRE_NOTEMPTY option to pcre_exec()
400 or pcre_dfa_exec(); if used twice, pass the
401 PCRE_NOTEMPTY_ATSTART option
402 \Odd set the size of the output vector passed to
403 pcre_exec() to dd (any number of digits)
404 \P pass the PCRE_PARTIAL_SOFT option to pcre_exec()
405 or pcre_dfa_exec(); if used twice, pass the
406 PCRE_PARTIAL_HARD option
407 \Qdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
408 (any number of digits)
409 \R pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
410 \S output details of memory get/free calls during matching
411 \Y pass the PCRE_NO_START_OPTIMIZE option to pcre_exec()
412 or pcre_dfa_exec()
413 \Z pass the PCRE_NOTEOL option to pcre_exec()
414 or pcre_dfa_exec()
415 \? pass the PCRE_NO_UTF8_CHECK option to
416 pcre_exec() or pcre_dfa_exec()
417 \>dd start the match at offset dd (optional "-"; then
418 any number of digits); this sets the startoffset
419 argument for pcre_exec() or pcre_dfa_exec()
420 \<cr> pass the PCRE_NEWLINE_CR option to pcre_exec()
421 or pcre_dfa_exec()
422 \<lf> pass the PCRE_NEWLINE_LF option to pcre_exec()
423 or pcre_dfa_exec()
424 \<crlf> pass the PCRE_NEWLINE_CRLF option to pcre_exec()
425 or pcre_dfa_exec()
426 \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
427 or pcre_dfa_exec()
428 \<any> pass the PCRE_NEWLINE_ANY option to pcre_exec()
429 or pcre_dfa_exec()
430
431 Note that \xhh always specifies one byte, even in UTF-8 mode; this
432 makes it possible to construct invalid UTF-8 sequences for testing pur-
433 poses. On the other hand, \x{hh} is interpreted as a UTF-8 character in
434 UTF-8 mode, generating more than one byte if the value is greater than
435 127. When not in UTF-8 mode, it generates one byte for values less than
436 256, and causes an error for greater values.
437
438 The escapes that specify line ending sequences are literal strings,
439 exactly as shown. No more than one newline setting should be present in
440 any data line.
441
442 A backslash followed by anything else just escapes the anything else.
443 If the very last character is a backslash, it is ignored. This gives a
444 way of passing an empty line as data, since a real empty line termi-
445 nates the data input.
446
447 If \M is present, pcretest calls pcre_exec() several times, with dif-
448 ferent values in the match_limit and match_limit_recursion fields of
449 the pcre_extra data structure, until it finds the minimum numbers for
450 each parameter that allow pcre_exec() to complete. The match_limit num-
451 ber is a measure of the amount of backtracking that takes place, and
452 checking it out can be instructive. For most simple matches, the number
453 is quite small, but for patterns with very large numbers of matching
454 possibilities, it can become large very quickly with increasing length
455 of subject string. The match_limit_recursion number is a measure of how
456 much stack (or, if PCRE is compiled with NO_RECURSE, how much heap)
457 memory is needed to complete the match attempt.
458
459 When \O is used, the value specified may be higher or lower than the
460 size set by the -O command line option (or defaulted to 45); \O applies
461 only to the call of pcre_exec() for the line in which it appears.
462
463 If the /P modifier was present on the pattern, causing the POSIX wrap-
464 per API to be used, the only option-setting sequences that have any
465 effect are \B, \N, and \Z, causing REG_NOTBOL, REG_NOTEMPTY, and
466 REG_NOTEOL, respectively, to be passed to regexec().
467
468 The use of \x{hh...} to represent UTF-8 characters is not dependent on
469 the use of the /8 modifier on the pattern. It is recognized always.
470 There may be any number of hexadecimal digits inside the braces. The
471 result is from one to six bytes, encoded according to the original
472 UTF-8 rules of RFC 2279. This allows for values in the range 0 to
473 0x7FFFFFFF. Note that not all of those are valid Unicode code points,
474 or indeed valid UTF-8 characters according to the later rules in RFC
475 3629.
476
477
478 THE ALTERNATIVE MATCHING FUNCTION
479
480 By default, pcretest uses the standard PCRE matching function,
481 pcre_exec() to match each data line. From release 6.0, PCRE supports an
482 alternative matching function, pcre_dfa_test(), which operates in a
483 different way, and has some restrictions. The differences between the
484 two functions are described in the pcrematching documentation.
485
486 If a data line contains the \D escape sequence, or if the command line
487 contains the -dfa option, the alternative matching function is called.
488 This function finds all possible matches at a given point. If, however,
489 the \F escape sequence is present in the data line, it stops after the
490 first match is found. This is always the shortest possible match.
491
492
493 DEFAULT OUTPUT FROM PCRETEST
494
495 This section describes the output when the normal matching function,
496 pcre_exec(), is being used.
497
498 When a match succeeds, pcretest outputs the list of captured substrings
499 that pcre_exec() returns, starting with number 0 for the string that
500 matched the whole pattern. Otherwise, it outputs "No match" when the
501 return is PCRE_ERROR_NOMATCH, and "Partial match:" followed by the par-
502 tially matching substring when pcre_exec() returns PCRE_ERROR_PARTIAL.
503 (Note that this is the entire substring that was inspected during the
504 partial match; it may include characters before the actual match start
505 if a lookbehind assertion, \K, \b, or \B was involved.) For any other
506 return, pcretest outputs the PCRE negative error number and a short
507 descriptive phrase. If the error is a failed UTF-8 string check, the
508 byte offset of the start of the failing character and the reason code
509 are also output, provided that the size of the output vector is at
510 least two. Here is an example of an interactive pcretest run.
511
512 $ pcretest
513 PCRE version 8.13 2011-04-30
514
515 re> /^abc(\d+)/
516 data> abc123
517 0: abc123
518 1: 123
519 data> xyz
520 No match
521
522 Unset capturing substrings that are not followed by one that is set are
523 not returned by pcre_exec(), and are not shown by pcretest. In the fol-
524 lowing example, there are two capturing substrings, but when the first
525 data line is matched, the second, unset substring is not shown. An
526 "internal" unset substring is shown as "<unset>", as for the second
527 data line.
528
529 re> /(a)|(b)/
530 data> a
531 0: a
532 1: a
533 data> b
534 0: b
535 1: <unset>
536 2: b
537
538 If the strings contain any non-printing characters, they are output as
539 \0x escapes, or as \x{...} escapes if the /8 modifier was present on
540 the pattern. See below for the definition of non-printing characters.
541 If the pattern has the /+ modifier, the output for substring 0 is fol-
542 lowed by the the rest of the subject string, identified by "0+" like
543 this:
544
545 re> /cat/+
546 data> cataract
547 0: cat
548 0+ aract
549
550 If the pattern has the /g or /G modifier, the results of successive
551 matching attempts are output in sequence, like this:
552
553 re> /\Bi(\w\w)/g
554 data> Mississippi
555 0: iss
556 1: ss
557 0: iss
558 1: ss
559 0: ipp
560 1: pp
561
562 "No match" is output only if the first match attempt fails. Here is an
563 example of a failure message (the offset 4 that is specified by \>4 is
564 past the end of the subject string):
565
566 re> /xyz/
567 data> xyz\>4
568 Error -24 (bad offset value)
569
570 If any of the sequences \C, \G, or \L are present in a data line that
571 is successfully matched, the substrings extracted by the convenience
572 functions are output with C, G, or L after the string number instead of
573 a colon. This is in addition to the normal full list. The string length
574 (that is, the return from the extraction function) is given in paren-
575 theses after each string for \C and \G.
576
577 Note that whereas patterns can be continued over several lines (a plain
578 ">" prompt is used for continuations), data lines may not. However new-
579 lines can be included in data by means of the \n escape (or \r, \r\n,
580 etc., depending on the newline sequence setting).
581
582
583 OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
584
585 When the alternative matching function, pcre_dfa_exec(), is used (by
586 means of the \D escape sequence or the -dfa command line option), the
587 output consists of a list of all the matches that start at the first
588 point in the subject where there is at least one match. For example:
589
590 re> /(tang|tangerine|tan)/
591 data> yellow tangerine\D
592 0: tangerine
593 1: tang
594 2: tan
595
596 (Using the normal matching function on this data finds only "tang".)
597 The longest matching string is always given first (and numbered zero).
598 After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", fol-
599 lowed by the partially matching substring. (Note that this is the
600 entire substring that was inspected during the partial match; it may
601 include characters before the actual match start if a lookbehind asser-
602 tion, \K, \b, or \B was involved.)
603
604 If /g is present on the pattern, the search for further matches resumes
605 at the end of the longest match. For example:
606
607 re> /(tang|tangerine|tan)/g
608 data> yellow tangerine and tangy sultana\D
609 0: tangerine
610 1: tang
611 2: tan
612 0: tang
613 1: tan
614 0: tan
615
616 Since the matching function does not support substring capture, the
617 escape sequences that are concerned with captured substrings are not
618 relevant.
619
620
621 RESTARTING AFTER A PARTIAL MATCH
622
623 When the alternative matching function has given the PCRE_ERROR_PARTIAL
624 return, indicating that the subject partially matched the pattern, you
625 can restart the match with additional subject data by means of the \R
626 escape sequence. For example:
627
628 re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
629 data> 23ja\P\D
630 Partial match: 23ja
631 data> n05\R\D
632 0: n05
633
634 For further information about partial matching, see the pcrepartial
635 documentation.
636
637
638 CALLOUTS
639
640 If the pattern contains any callout requests, pcretest's callout func-
641 tion is called during matching. This works with both matching func-
642 tions. By default, the called function displays the callout number, the
643 start and current positions in the text at the callout time, and the
644 next pattern item to be tested. For example, the output
645
646 --->pqrabcdef
647 0 ^ ^ \d
648
649 indicates that callout number 0 occurred for a match attempt starting
650 at the fourth character of the subject string, when the pointer was at
651 the seventh character of the data, and when the next pattern item was
652 \d. Just one circumflex is output if the start and current positions
653 are the same.
654
655 Callouts numbered 255 are assumed to be automatic callouts, inserted as
656 a result of the /C pattern modifier. In this case, instead of showing
657 the callout number, the offset in the pattern, preceded by a plus, is
658 output. For example:
659
660 re> /\d?[A-E]\*/C
661 data> E*
662 --->E*
663 +0 ^ \d?
664 +3 ^ [A-E]
665 +8 ^^ \*
666 +10 ^ ^
667 0: E*
668
669 If a pattern contains (*MARK) items, an additional line is output when-
670 ever a change of latest mark is passed to the callout function. For
671 example:
672
673 re> /a(*MARK:X)bc/C
674 data> abc
675 --->abc
676 +0 ^ a
677 +1 ^^ (*MARK:X)
678 +10 ^^ b
679 Latest Mark: X
680 +11 ^ ^ c
681 +12 ^ ^
682 0: abc
683
684 The mark changes between matching "a" and "b", but stays the same for
685 the rest of the match, so nothing more is output. If, as a result of
686 backtracking, the mark reverts to being unset, the text "<unset>" is
687 output.
688
689 The callout function in pcretest returns zero (carry on matching) by
690 default, but you can use a \C item in a data line (as described above)
691 to change this and other parameters of the callout.
692
693 Inserting callouts can be helpful when using pcretest to check compli-
694 cated regular expressions. For further information about callouts, see
695 the pcrecallout documentation.
696
697
698 NON-PRINTING CHARACTERS
699
700 When pcretest is outputting text in the compiled version of a pattern,
701 bytes other than 32-126 are always treated as non-printing characters
702 are are therefore shown as hex escapes.
703
704 When pcretest is outputting text that is a matched part of a subject
705 string, it behaves in the same way, unless a different locale has been
706 set for the pattern (using the /L modifier). In this case, the
707 isprint() function to distinguish printing and non-printing characters.
708
709
710 SAVING AND RELOADING COMPILED PATTERNS
711
712 The facilities described in this section are not available when the
713 POSIX interface to PCRE is being used, that is, when the /P pattern
714 modifier is specified.
715
716 When the POSIX interface is not in use, you can cause pcretest to write
717 a compiled pattern to a file, by following the modifiers with > and a
718 file name. For example:
719
720 /pattern/im >/some/file
721
722 See the pcreprecompile documentation for a discussion about saving and
723 re-using compiled patterns.
724
725 The data that is written is binary. The first eight bytes are the
726 length of the compiled pattern data followed by the length of the
727 optional study data, each written as four bytes in big-endian order
728 (most significant byte first). If there is no study data (either the
729 pattern was not studied, or studying did not return any data), the sec-
730 ond length is zero. The lengths are followed by an exact copy of the
731 compiled pattern. If there is additional study data, this follows imme-
732 diately after the compiled pattern. After writing the file, pcretest
733 expects to read a new pattern.
734
735 A saved pattern can be reloaded into pcretest by specifying < and a
736 file name instead of a pattern. The name of the file must not contain a
737 < character, as otherwise pcretest will interpret the line as a pattern
738 delimited by < characters. For example:
739
740 re> </some/file
741 Compiled pattern loaded from /some/file
742 No study data
743
744 When the pattern has been loaded, pcretest proceeds to read data lines
745 in the usual way.
746
747 You can copy a file written by pcretest to a different host and reload
748 it there, even if the new host has opposite endianness to the one on
749 which the pattern was compiled. For example, you can compile on an i86
750 machine and run on a SPARC machine.
751
752 File names for saving and reloading can be absolute or relative, but
753 note that the shell facility of expanding a file name that starts with
754 a tilde (~) is not available.
755
756 The ability to save and reload files in pcretest is intended for test-
757 ing and experimentation. It is not intended for production use because
758 only a single pattern can be written to a file. Furthermore, there is
759 no facility for supplying custom character tables for use with a
760 reloaded pattern. If the original pattern was compiled with custom
761 tables, an attempt to match a subject string using a reloaded pattern
762 is likely to cause pcretest to crash. Finally, if you attempt to load
763 a file that is not in the correct format, the result is undefined.
764
765
766 SEE ALSO
767
768 pcre(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcrepartial(d),
769 pcrepattern(3), pcreprecompile(3).
770
771
772 AUTHOR
773
774 Philip Hazel
775 University Computing Service
776 Cambridge CB2 3QH, England.
777
778
779 REVISION
780
781 Last updated: 01 August 2011
782 Copyright (c) 1997-2011 University of Cambridge.

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