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Revision 455 - (show annotations)
Sat Sep 26 19:12:32 2009 UTC (11 years, 7 months ago) by ph10
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Error occurred while calculating annotation data.
Added lower bound length-finding to pcre_study() and use it when matching; make 
the value available via pcre_fullinfo(); also fixed bugs connected with
pcre_study() in pcre_dfa_exec(). 
3 pcretest - a program for testing Perl-compatible regular expressions.
5 .rs
6 .sp
7 .B pcretest "[options] [source] [destination]"
8 .sp
9 \fBpcretest\fP was written as a test program for the PCRE regular expression
10 library itself, but it can also be used for experimenting with regular
11 expressions. This document describes the features of the test program; for
12 details of the regular expressions themselves, see the
13 .\" HREF
14 \fBpcrepattern\fP
15 .\"
16 documentation. For details of the PCRE library function calls and their
17 options, see the
18 .\" HREF
19 \fBpcreapi\fP
20 .\"
21 documentation.
22 .
23 .
25 .rs
26 .TP 10
27 \fB-b\fP
28 Behave as if each regex has the \fB/B\fP (show bytecode) modifier; the internal
29 form is output after compilation.
30 .TP 10
31 \fB-C\fP
32 Output the version number of the PCRE library, and all available information
33 about the optional features that are included, and then exit.
34 .TP 10
35 \fB-d\fP
36 Behave as if each regex has the \fB/D\fP (debug) modifier; the internal
37 form and information about the compiled pattern is output after compilation;
38 \fB-d\fP is equivalent to \fB-b -i\fP.
39 .TP 10
40 \fB-dfa\fP
41 Behave as if each data line contains the \eD escape sequence; this causes the
42 alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
43 standard \fBpcre_exec()\fP function (more detail is given below).
44 .TP 10
45 \fB-help\fP
46 Output a brief summary these options and then exit.
47 .TP 10
48 \fB-i\fP
49 Behave as if each regex has the \fB/I\fP modifier; information about the
50 compiled pattern is given after compilation.
51 .TP 10
52 \fB-M\fP
53 Behave as if each data line contains the \eM escape sequence; this causes
54 PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by
55 calling \fBpcre_exec()\fP repeatedly with different limits.
56 .TP 10
57 \fB-m\fP
58 Output the size of each compiled pattern after it has been compiled. This is
59 equivalent to adding \fB/M\fP to each regular expression. For compatibility
60 with earlier versions of pcretest, \fB-s\fP is a synonym for \fB-m\fP.
61 .TP 10
62 \fB-o\fP \fIosize\fP
63 Set the number of elements in the output vector that is used when calling
64 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
65 is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
66 22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
67 changed for individual matching calls by including \eO in the data line (see
68 below).
69 .TP 10
70 \fB-p\fP
71 Behave as if each regex has the \fB/P\fP modifier; the POSIX wrapper API is
72 used to call PCRE. None of the other options has any effect when \fB-p\fP is
73 set.
74 .TP 10
75 \fB-q\fP
76 Do not output the version number of \fBpcretest\fP at the start of execution.
77 .TP 10
78 \fB-S\fP \fIsize\fP
79 On Unix-like systems, set the size of the runtime stack to \fIsize\fP
80 megabytes.
81 .TP 10
82 \fB-t\fP
83 Run each compile, study, and match many times with a timer, and output
84 resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
85 \fB-t\fP, because you will then get the size output a zillion times, and the
86 timing will be distorted. You can control the number of iterations that are
87 used for timing by following \fB-t\fP with a number (as a separate item on the
88 command line). For example, "-t 1000" would iterate 1000 times. The default is
89 to iterate 500000 times.
90 .TP 10
91 \fB-tm\fP
92 This is like \fB-t\fP except that it times only the matching phase, not the
93 compile or study phases.
94 .
95 .
97 .rs
98 .sp
99 If \fBpcretest\fP is given two filename arguments, it reads from the first and
100 writes to the second. If it is given only one filename argument, it reads from
101 that file and writes to stdout. Otherwise, it reads from stdin and writes to
102 stdout, and prompts for each line of input, using "re>" to prompt for regular
103 expressions, and "data>" to prompt for data lines.
104 .P
105 When \fBpcretest\fP is built, a configuration option can specify that it should
106 be linked with the \fBlibreadline\fP library. When this is done, if the input
107 is from a terminal, it is read using the \fBreadline()\fP function. This
108 provides line-editing and history facilities. The output from the \fB-help\fP
109 option states whether or not \fBreadline()\fP will be used.
110 .P
111 The program handles any number of sets of input on a single input file. Each
112 set starts with a regular expression, and continues with any number of data
113 lines to be matched against the pattern.
114 .P
115 Each data line is matched separately and independently. If you want to do
116 multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
117 etc., depending on the newline setting) in a single line of input to encode the
118 newline sequences. There is no limit on the length of data lines; the input
119 buffer is automatically extended if it is too small.
120 .P
121 An empty line signals the end of the data lines, at which point a new regular
122 expression is read. The regular expressions are given enclosed in any
123 non-alphanumeric delimiters other than backslash, for example:
124 .sp
125 /(a|bc)x+yz/
126 .sp
127 White space before the initial delimiter is ignored. A regular expression may
128 be continued over several input lines, in which case the newline characters are
129 included within it. It is possible to include the delimiter within the pattern
130 by escaping it, for example
131 .sp
132 /abc\e/def/
133 .sp
134 If you do so, the escape and the delimiter form part of the pattern, but since
135 delimiters are always non-alphanumeric, this does not affect its interpretation.
136 If the terminating delimiter is immediately followed by a backslash, for
137 example,
138 .sp
139 /abc/\e
140 .sp
141 then a backslash is added to the end of the pattern. This is done to provide a
142 way of testing the error condition that arises if a pattern finishes with a
143 backslash, because
144 .sp
145 /abc\e/
146 .sp
147 is interpreted as the first line of a pattern that starts with "abc/", causing
148 pcretest to read the next line as a continuation of the regular expression.
149 .
150 .
152 .rs
153 .sp
154 A pattern may be followed by any number of modifiers, which are mostly single
155 characters. Following Perl usage, these are referred to below as, for example,
156 "the \fB/i\fP modifier", even though the delimiter of the pattern need not
157 always be a slash, and no slash is used when writing modifiers. Whitespace may
158 appear between the final pattern delimiter and the first modifier, and between
159 the modifiers themselves.
160 .P
161 The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
162 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
163 \fBpcre_compile()\fP is called. These four modifier letters have the same
164 effect as they do in Perl. For example:
165 .sp
166 /caseless/i
167 .sp
168 The following table shows additional modifiers for setting PCRE options that do
169 not correspond to anything in Perl:
170 .sp
180 \fB/<cr>\fP PCRE_NEWLINE_CR
181 \fB/<lf>\fP PCRE_NEWLINE_LF
182 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
183 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
184 \fB/<any>\fP PCRE_NEWLINE_ANY
185 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
186 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
187 .sp
188 Those specifying line ending sequences are literal strings as shown, but the
189 letters can be in either case. This example sets multiline matching with CRLF
190 as the line ending sequence:
191 .sp
192 /^abc/m<crlf>
193 .sp
194 Details of the meanings of these PCRE options are given in the
195 .\" HREF
196 \fBpcreapi\fP
197 .\"
198 documentation.
199 .
200 .
201 .SS "Finding all matches in a string"
202 .rs
203 .sp
204 Searching for all possible matches within each subject string can be requested
205 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
206 again to search the remainder of the subject string. The difference between
207 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
208 \fBpcre_exec()\fP to start searching at a new point within the entire string
209 (which is in effect what Perl does), whereas the latter passes over a shortened
210 substring. This makes a difference to the matching process if the pattern
211 begins with a lookbehind assertion (including \eb or \eB).
212 .P
213 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
214 empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and
215 PCRE_ANCHORED flags set in order to search for another, non-empty, match at the
216 same point. If this second match fails, the start offset is advanced by one
217 character, and the normal match is retried. This imitates the way Perl handles
218 such cases when using the \fB/g\fP modifier or the \fBsplit()\fP function.
219 .
220 .
221 .SS "Other modifiers"
222 .rs
223 .sp
224 There are yet more modifiers for controlling the way \fBpcretest\fP
225 operates.
226 .P
227 The \fB/+\fP modifier requests that as well as outputting the substring that
228 matched the entire pattern, pcretest should in addition output the remainder of
229 the subject string. This is useful for tests where the subject contains
230 multiple copies of the same substring.
231 .P
232 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
233 output a representation of the compiled byte code after compilation. Normally
234 this information contains length and offset values; however, if \fB/Z\fP is
235 also present, this data is replaced by spaces. This is a special feature for
236 use in the automatic test scripts; it ensures that the same output is generated
237 for different internal link sizes.
238 .P
239 The \fB/L\fP modifier must be followed directly by the name of a locale, for
240 example,
241 .sp
242 /pattern/Lfr_FR
243 .sp
244 For this reason, it must be the last modifier. The given locale is set,
245 \fBpcre_maketables()\fP is called to build a set of character tables for the
246 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
247 regular expression. Without an \fB/L\fP modifier, NULL is passed as the tables
248 pointer; that is, \fB/L\fP applies only to the expression on which it appears.
249 .P
250 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
251 compiled pattern (whether it is anchored, has a fixed first character, and
252 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
253 pattern. If the pattern is studied, the results of that are also output.
254 .P
255 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
256 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
257 .P
258 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
259 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
260 facility is for testing the feature in PCRE that allows it to execute patterns
261 that were compiled on a host with a different endianness. This feature is not
262 available when the POSIX interface to PCRE is being used, that is, when the
263 \fB/P\fP pattern modifier is specified. See also the section about saving and
264 reloading compiled patterns below.
265 .P
266 The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
267 expression has been compiled, and the results used when the expression is
268 matched.
269 .P
270 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
271 pattern to be output.
272 .P
273 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
274 API rather than its native API. When this is done, all other modifiers except
275 \fB/i\fP, \fB/m\fP, and \fB/+\fP are ignored. REG_ICASE is set if \fB/i\fP is
276 present, and REG_NEWLINE is set if \fB/m\fP is present. The wrapper functions
277 force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
278 .P
279 The \fB/8\fP modifier causes \fBpcretest\fP to call PCRE with the PCRE_UTF8
280 option set. This turns on support for UTF-8 character handling in PCRE,
281 provided that it was compiled with this support enabled. This modifier also
282 causes any non-printing characters in output strings to be printed using the
283 \ex{hh...} notation if they are valid UTF-8 sequences.
284 .P
285 If the \fB/?\fP modifier is used with \fB/8\fP, it causes \fBpcretest\fP to
286 call \fBpcre_compile()\fP with the PCRE_NO_UTF8_CHECK option, to suppress the
287 checking of the string for UTF-8 validity.
288 .
289 .
291 .rs
292 .sp
293 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
294 whitespace is removed, and it is then scanned for \e escapes. Some of these are
295 pretty esoteric features, intended for checking out some of the more
296 complicated features of PCRE. If you are just testing "ordinary" regular
297 expressions, you probably don't need any of these. The following escapes are
298 recognized:
299 .sp
300 \ea alarm (BEL, \ex07)
301 \eb backspace (\ex08)
302 \ee escape (\ex27)
303 \ef formfeed (\ex0c)
304 \en newline (\ex0a)
305 .\" JOIN
306 \eqdd set the PCRE_MATCH_LIMIT limit to dd
307 (any number of digits)
308 \er carriage return (\ex0d)
309 \et tab (\ex09)
310 \ev vertical tab (\ex0b)
311 \ennn octal character (up to 3 octal digits)
312 \exhh hexadecimal character (up to 2 hex digits)
313 .\" JOIN
314 \ex{hh...} hexadecimal character, any number of digits
315 in UTF-8 mode
316 .\" JOIN
317 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
318 or \fBpcre_dfa_exec()\fP
319 .\" JOIN
320 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
321 or \fBpcre_dfa_exec()\fP
322 .\" JOIN
323 \eCdd call pcre_copy_substring() for substring dd
324 after a successful match (number less than 32)
325 .\" JOIN
326 \eCname call pcre_copy_named_substring() for substring
327 "name" after a successful match (name termin-
328 ated by next non alphanumeric character)
329 .\" JOIN
330 \eC+ show the current captured substrings at callout
331 time
332 \eC- do not supply a callout function
333 .\" JOIN
334 \eC!n return 1 instead of 0 when callout number n is
335 reached
336 .\" JOIN
337 \eC!n!m return 1 instead of 0 when callout number n is
338 reached for the nth time
339 .\" JOIN
340 \eC*n pass the number n (may be negative) as callout
341 data; this is used as the callout return value
342 \eD use the \fBpcre_dfa_exec()\fP match function
343 \eF only shortest match for \fBpcre_dfa_exec()\fP
344 .\" JOIN
345 \eGdd call pcre_get_substring() for substring dd
346 after a successful match (number less than 32)
347 .\" JOIN
348 \eGname call pcre_get_named_substring() for substring
349 "name" after a successful match (name termin-
350 ated by next non-alphanumeric character)
351 .\" JOIN
352 \eL call pcre_get_substringlist() after a
353 successful match
354 .\" JOIN
355 \eM discover the minimum MATCH_LIMIT and
357 .\" JOIN
358 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
359 or \fBpcre_dfa_exec()\fP; if used twice, pass the
361 .\" JOIN
362 \eOdd set the size of the output vector passed to
363 \fBpcre_exec()\fP to dd (any number of digits)
364 .\" JOIN
365 \eP pass the PCRE_PARTIAL_SOFT option to \fBpcre_exec()\fP
366 or \fBpcre_dfa_exec()\fP; if used twice, pass the
368 .\" JOIN
369 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
370 (any number of digits)
371 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
372 \eS output details of memory get/free calls during matching
373 .\" JOIN
374 \eY pass the PCRE_NO_START_OPTIMIZE option to \fBpcre_exec()\fP
375 or \fBpcre_dfa_exec()\fP
376 .\" JOIN
377 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
378 or \fBpcre_dfa_exec()\fP
379 .\" JOIN
380 \e? pass the PCRE_NO_UTF8_CHECK option to
381 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
382 \e>dd start the match at offset dd (any number of digits);
383 .\" JOIN
384 this sets the \fIstartoffset\fP argument for \fBpcre_exec()\fP
385 or \fBpcre_dfa_exec()\fP
386 .\" JOIN
387 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
388 or \fBpcre_dfa_exec()\fP
389 .\" JOIN
390 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
391 or \fBpcre_dfa_exec()\fP
392 .\" JOIN
393 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
394 or \fBpcre_dfa_exec()\fP
395 .\" JOIN
396 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
397 or \fBpcre_dfa_exec()\fP
398 .\" JOIN
399 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
400 or \fBpcre_dfa_exec()\fP
401 .sp
402 The escapes that specify line ending sequences are literal strings, exactly as
403 shown. No more than one newline setting should be present in any data line.
404 .P
405 A backslash followed by anything else just escapes the anything else. If
406 the very last character is a backslash, it is ignored. This gives a way of
407 passing an empty line as data, since a real empty line terminates the data
408 input.
409 .P
410 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
411 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
412 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
413 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
414 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
415 place, and checking it out can be instructive. For most simple matches, the
416 number is quite small, but for patterns with very large numbers of matching
417 possibilities, it can become large very quickly with increasing length of
418 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
419 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
420 to complete the match attempt.
421 .P
422 When \eO is used, the value specified may be higher or lower than the size set
423 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
424 the call of \fBpcre_exec()\fP for the line in which it appears.
425 .P
426 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
427 API to be used, the only option-setting sequences that have any effect are \eB
428 and \eZ, causing REG_NOTBOL and REG_NOTEOL, respectively, to be passed to
429 \fBregexec()\fP.
430 .P
431 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
432 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
433 any number of hexadecimal digits inside the braces. The result is from one to
434 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
435 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
436 valid Unicode code points, or indeed valid UTF-8 characters according to the
437 later rules in RFC 3629.
438 .
439 .
441 .rs
442 .sp
443 By default, \fBpcretest\fP uses the standard PCRE matching function,
444 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
445 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
446 different way, and has some restrictions. The differences between the two
447 functions are described in the
448 .\" HREF
449 \fBpcrematching\fP
450 .\"
451 documentation.
452 .P
453 If a data line contains the \eD escape sequence, or if the command line
454 contains the \fB-dfa\fP option, the alternative matching function is called.
455 This function finds all possible matches at a given point. If, however, the \eF
456 escape sequence is present in the data line, it stops after the first match is
457 found. This is always the shortest possible match.
458 .
459 .
461 .rs
462 .sp
463 This section describes the output when the normal matching function,
464 \fBpcre_exec()\fP, is being used.
465 .P
466 When a match succeeds, pcretest outputs the list of captured substrings that
467 \fBpcre_exec()\fP returns, starting with number 0 for the string that matched
468 the whole pattern. Otherwise, it outputs "No match" when the return is
469 PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching
470 substring when \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL. For any other
471 returns, it outputs the PCRE negative error number. Here is an example of an
472 interactive \fBpcretest\fP run.
473 .sp
474 $ pcretest
475 PCRE version 7.0 30-Nov-2006
476 .sp
477 re> /^abc(\ed+)/
478 data> abc123
479 0: abc123
480 1: 123
481 data> xyz
482 No match
483 .sp
484 Note that unset capturing substrings that are not followed by one that is set
485 are not returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In
486 the following example, there are two capturing substrings, but when the first
487 data line is matched, the second, unset substring is not shown. An "internal"
488 unset substring is shown as "<unset>", as for the second data line.
489 .sp
490 re> /(a)|(b)/
491 data> a
492 0: a
493 1: a
494 data> b
495 0: b
496 1: <unset>
497 2: b
498 .sp
499 If the strings contain any non-printing characters, they are output as \e0x
500 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
501 pattern. See below for the definition of non-printing characters. If the
502 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
503 the the rest of the subject string, identified by "0+" like this:
504 .sp
505 re> /cat/+
506 data> cataract
507 0: cat
508 0+ aract
509 .sp
510 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
511 matching attempts are output in sequence, like this:
512 .sp
513 re> /\eBi(\ew\ew)/g
514 data> Mississippi
515 0: iss
516 1: ss
517 0: iss
518 1: ss
519 0: ipp
520 1: pp
521 .sp
522 "No match" is output only if the first match attempt fails.
523 .P
524 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
525 data line that is successfully matched, the substrings extracted by the
526 convenience functions are output with C, G, or L after the string number
527 instead of a colon. This is in addition to the normal full list. The string
528 length (that is, the return from the extraction function) is given in
529 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
530 .P
531 Note that whereas patterns can be continued over several lines (a plain ">"
532 prompt is used for continuations), data lines may not. However newlines can be
533 included in data by means of the \en escape (or \er, \er\en, etc., depending on
534 the newline sequence setting).
535 .
536 .
537 .
539 .rs
540 .sp
541 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
542 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
543 output consists of a list of all the matches that start at the first point in
544 the subject where there is at least one match. For example:
545 .sp
546 re> /(tang|tangerine|tan)/
547 data> yellow tangerine\eD
548 0: tangerine
549 1: tang
550 2: tan
551 .sp
552 (Using the normal matching function on this data finds only "tang".) The
553 longest matching string is always given first (and numbered zero). After a
554 PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the
555 partially matching substring.
556 .P
557 If \fB/g\fP is present on the pattern, the search for further matches resumes
558 at the end of the longest match. For example:
559 .sp
560 re> /(tang|tangerine|tan)/g
561 data> yellow tangerine and tangy sultana\eD
562 0: tangerine
563 1: tang
564 2: tan
565 0: tang
566 1: tan
567 0: tan
568 .sp
569 Since the matching function does not support substring capture, the escape
570 sequences that are concerned with captured substrings are not relevant.
571 .
572 .
574 .rs
575 .sp
576 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
577 indicating that the subject partially matched the pattern, you can restart the
578 match with additional subject data by means of the \eR escape sequence. For
579 example:
580 .sp
581 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
582 data> 23ja\eP\eD
583 Partial match: 23ja
584 data> n05\eR\eD
585 0: n05
586 .sp
587 For further information about partial matching, see the
588 .\" HREF
589 \fBpcrepartial\fP
590 .\"
591 documentation.
592 .
593 .
595 .rs
596 .sp
597 If the pattern contains any callout requests, \fBpcretest\fP's callout function
598 is called during matching. This works with both matching functions. By default,
599 the called function displays the callout number, the start and current
600 positions in the text at the callout time, and the next pattern item to be
601 tested. For example, the output
602 .sp
603 --->pqrabcdef
604 0 ^ ^ \ed
605 .sp
606 indicates that callout number 0 occurred for a match attempt starting at the
607 fourth character of the subject string, when the pointer was at the seventh
608 character of the data, and when the next pattern item was \ed. Just one
609 circumflex is output if the start and current positions are the same.
610 .P
611 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
612 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
613 callout number, the offset in the pattern, preceded by a plus, is output. For
614 example:
615 .sp
616 re> /\ed?[A-E]\e*/C
617 data> E*
618 --->E*
619 +0 ^ \ed?
620 +3 ^ [A-E]
621 +8 ^^ \e*
622 +10 ^ ^
623 0: E*
624 .sp
625 The callout function in \fBpcretest\fP returns zero (carry on matching) by
626 default, but you can use a \eC item in a data line (as described above) to
627 change this.
628 .P
629 Inserting callouts can be helpful when using \fBpcretest\fP to check
630 complicated regular expressions. For further information about callouts, see
631 the
632 .\" HREF
633 \fBpcrecallout\fP
634 .\"
635 documentation.
636 .
637 .
638 .
640 .rs
641 .sp
642 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
643 bytes other than 32-126 are always treated as non-printing characters are are
644 therefore shown as hex escapes.
645 .P
646 When \fBpcretest\fP is outputting text that is a matched part of a subject
647 string, it behaves in the same way, unless a different locale has been set for
648 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
649 function to distinguish printing and non-printing characters.
650 .
651 .
652 .
654 .rs
655 .sp
656 The facilities described in this section are not available when the POSIX
657 inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
658 specified.
659 .P
660 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
661 compiled pattern to a file, by following the modifiers with > and a file name.
662 For example:
663 .sp
664 /pattern/im >/some/file
665 .sp
666 See the
667 .\" HREF
668 \fBpcreprecompile\fP
669 .\"
670 documentation for a discussion about saving and re-using compiled patterns.
671 .P
672 The data that is written is binary. The first eight bytes are the length of the
673 compiled pattern data followed by the length of the optional study data, each
674 written as four bytes in big-endian order (most significant byte first). If
675 there is no study data (either the pattern was not studied, or studying did not
676 return any data), the second length is zero. The lengths are followed by an
677 exact copy of the compiled pattern. If there is additional study data, this
678 follows immediately after the compiled pattern. After writing the file,
679 \fBpcretest\fP expects to read a new pattern.
680 .P
681 A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
682 name instead of a pattern. The name of the file must not contain a < character,
683 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
684 characters.
685 For example:
686 .sp
687 re> </some/file
688 Compiled regex loaded from /some/file
689 No study data
690 .sp
691 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
692 the usual way.
693 .P
694 You can copy a file written by \fBpcretest\fP to a different host and reload it
695 there, even if the new host has opposite endianness to the one on which the
696 pattern was compiled. For example, you can compile on an i86 machine and run on
697 a SPARC machine.
698 .P
699 File names for saving and reloading can be absolute or relative, but note that
700 the shell facility of expanding a file name that starts with a tilde (~) is not
701 available.
702 .P
703 The ability to save and reload files in \fBpcretest\fP is intended for testing
704 and experimentation. It is not intended for production use because only a
705 single pattern can be written to a file. Furthermore, there is no facility for
706 supplying custom character tables for use with a reloaded pattern. If the
707 original pattern was compiled with custom tables, an attempt to match a subject
708 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
709 Finally, if you attempt to load a file that is not in the correct format, the
710 result is undefined.
711 .
712 .
713 .SH "SEE ALSO"
714 .rs
715 .sp
716 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
717 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
718 .
719 .
721 .rs
722 .sp
723 .nf
724 Philip Hazel
725 University Computing Service
726 Cambridge CB2 3QH, England.
727 .fi
728 .
729 .
731 .rs
732 .sp
733 .nf
734 Last updated: 26 September 2009
735 Copyright (c) 1997-2009 University of Cambridge.
736 .fi


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