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Mon Nov 19 10:09:04 2007 UTC (13 years, 10 months ago) by ph10
File size: 27959 byte(s)
Update pcretest doc to clarify the output for unset substrings.
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 Output the size of each compiled pattern after it has been compiled. This is
54 equivalent to adding \fB/M\fP to each regular expression. For compatibility
55 with earlier versions of pcretest, \fB-s\fP is a synonym for \fB-m\fP.
56 .TP 10
57 \fB-o\fP \fIosize\fP
58 Set the number of elements in the output vector that is used when calling
59 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
60 is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
61 22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
62 changed for individual matching calls by including \eO in the data line (see
63 below).
64 .TP 10
65 \fB-p\fP
66 Behave as if each regex has the \fB/P\fP modifier; the POSIX wrapper API is
67 used to call PCRE. None of the other options has any effect when \fB-p\fP is
68 set.
69 .TP 10
70 \fB-q\fP
71 Do not output the version number of \fBpcretest\fP at the start of execution.
72 .TP 10
73 \fB-S\fP \fIsize\fP
74 On Unix-like systems, set the size of the runtime stack to \fIsize\fP
75 megabytes.
76 .TP 10
77 \fB-t\fP
78 Run each compile, study, and match many times with a timer, and output
79 resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
80 \fB-t\fP, because you will then get the size output a zillion times, and the
81 timing will be distorted. You can control the number of iterations that are
82 used for timing by following \fB-t\fP with a number (as a separate item on the
83 command line). For example, "-t 1000" would iterate 1000 times. The default is
84 to iterate 500000 times.
85 .TP 10
86 \fB-tm\fP
87 This is like \fB-t\fP except that it times only the matching phase, not the
88 compile or study phases.
89 .
90 .
92 .rs
93 .sp
94 If \fBpcretest\fP is given two filename arguments, it reads from the first and
95 writes to the second. If it is given only one filename argument, it reads from
96 that file and writes to stdout. Otherwise, it reads from stdin and writes to
97 stdout, and prompts for each line of input, using "re>" to prompt for regular
98 expressions, and "data>" to prompt for data lines.
99 .P
100 The program handles any number of sets of input on a single input file. Each
101 set starts with a regular expression, and continues with any number of data
102 lines to be matched against the pattern.
103 .P
104 Each data line is matched separately and independently. If you want to do
105 multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
106 etc., depending on the newline setting) in a single line of input to encode the
107 newline sequences. There is no limit on the length of data lines; the input
108 buffer is automatically extended if it is too small.
109 .P
110 An empty line signals the end of the data lines, at which point a new regular
111 expression is read. The regular expressions are given enclosed in any
112 non-alphanumeric delimiters other than backslash, for example:
113 .sp
114 /(a|bc)x+yz/
115 .sp
116 White space before the initial delimiter is ignored. A regular expression may
117 be continued over several input lines, in which case the newline characters are
118 included within it. It is possible to include the delimiter within the pattern
119 by escaping it, for example
120 .sp
121 /abc\e/def/
122 .sp
123 If you do so, the escape and the delimiter form part of the pattern, but since
124 delimiters are always non-alphanumeric, this does not affect its interpretation.
125 If the terminating delimiter is immediately followed by a backslash, for
126 example,
127 .sp
128 /abc/\e
129 .sp
130 then a backslash is added to the end of the pattern. This is done to provide a
131 way of testing the error condition that arises if a pattern finishes with a
132 backslash, because
133 .sp
134 /abc\e/
135 .sp
136 is interpreted as the first line of a pattern that starts with "abc/", causing
137 pcretest to read the next line as a continuation of the regular expression.
138 .
139 .
141 .rs
142 .sp
143 A pattern may be followed by any number of modifiers, which are mostly single
144 characters. Following Perl usage, these are referred to below as, for example,
145 "the \fB/i\fP modifier", even though the delimiter of the pattern need not
146 always be a slash, and no slash is used when writing modifiers. Whitespace may
147 appear between the final pattern delimiter and the first modifier, and between
148 the modifiers themselves.
149 .P
150 The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
151 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
152 \fBpcre_compile()\fP is called. These four modifier letters have the same
153 effect as they do in Perl. For example:
154 .sp
155 /caseless/i
156 .sp
157 The following table shows additional modifiers for setting PCRE options that do
158 not correspond to anything in Perl:
159 .sp
168 \fB/<cr>\fP PCRE_NEWLINE_CR
169 \fB/<lf>\fP PCRE_NEWLINE_LF
170 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
171 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
172 \fB/<any>\fP PCRE_NEWLINE_ANY
173 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
174 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
175 .sp
176 Those specifying line ending sequences are literal strings as shown, but the
177 letters can be in either case. This example sets multiline matching with CRLF
178 as the line ending sequence:
179 .sp
180 /^abc/m<crlf>
181 .sp
182 Details of the meanings of these PCRE options are given in the
183 .\" HREF
184 \fBpcreapi\fP
185 .\"
186 documentation.
187 .
188 .
189 .SS "Finding all matches in a string"
190 .rs
191 .sp
192 Searching for all possible matches within each subject string can be requested
193 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
194 again to search the remainder of the subject string. The difference between
195 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
196 \fBpcre_exec()\fP to start searching at a new point within the entire string
197 (which is in effect what Perl does), whereas the latter passes over a shortened
198 substring. This makes a difference to the matching process if the pattern
199 begins with a lookbehind assertion (including \eb or \eB).
200 .P
201 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
202 empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
203 flags set in order to search for another, non-empty, match at the same point.
204 If this second match fails, the start offset is advanced by one, and the normal
205 match is retried. This imitates the way Perl handles such cases when using the
206 \fB/g\fP modifier or the \fBsplit()\fP function.
207 .
208 .
209 .SS "Other modifiers"
210 .rs
211 .sp
212 There are yet more modifiers for controlling the way \fBpcretest\fP
213 operates.
214 .P
215 The \fB/+\fP modifier requests that as well as outputting the substring that
216 matched the entire pattern, pcretest should in addition output the remainder of
217 the subject string. This is useful for tests where the subject contains
218 multiple copies of the same substring.
219 .P
220 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
221 output a representation of the compiled byte code after compilation. Normally
222 this information contains length and offset values; however, if \fB/Z\fP is
223 also present, this data is replaced by spaces. This is a special feature for
224 use in the automatic test scripts; it ensures that the same output is generated
225 for different internal link sizes.
226 .P
227 The \fB/L\fP modifier must be followed directly by the name of a locale, for
228 example,
229 .sp
230 /pattern/Lfr_FR
231 .sp
232 For this reason, it must be the last modifier. The given locale is set,
233 \fBpcre_maketables()\fP is called to build a set of character tables for the
234 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
235 regular expression. Without an \fB/L\fP modifier, NULL is passed as the tables
236 pointer; that is, \fB/L\fP applies only to the expression on which it appears.
237 .P
238 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
239 compiled pattern (whether it is anchored, has a fixed first character, and
240 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
241 pattern. If the pattern is studied, the results of that are also output.
242 .P
243 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
244 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
245 .P
246 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
247 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
248 facility is for testing the feature in PCRE that allows it to execute patterns
249 that were compiled on a host with a different endianness. This feature is not
250 available when the POSIX interface to PCRE is being used, that is, when the
251 \fB/P\fP pattern modifier is specified. See also the section about saving and
252 reloading compiled patterns below.
253 .P
254 The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
255 expression has been compiled, and the results used when the expression is
256 matched.
257 .P
258 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
259 pattern to be output.
260 .P
261 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
262 API rather than its native API. When this is done, all other modifiers except
263 \fB/i\fP, \fB/m\fP, and \fB/+\fP are ignored. REG_ICASE is set if \fB/i\fP is
264 present, and REG_NEWLINE is set if \fB/m\fP is present. The wrapper functions
265 force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
266 .P
267 The \fB/8\fP modifier causes \fBpcretest\fP to call PCRE with the PCRE_UTF8
268 option set. This turns on support for UTF-8 character handling in PCRE,
269 provided that it was compiled with this support enabled. This modifier also
270 causes any non-printing characters in output strings to be printed using the
271 \ex{hh...} notation if they are valid UTF-8 sequences.
272 .P
273 If the \fB/?\fP modifier is used with \fB/8\fP, it causes \fBpcretest\fP to
274 call \fBpcre_compile()\fP with the PCRE_NO_UTF8_CHECK option, to suppress the
275 checking of the string for UTF-8 validity.
276 .
277 .
279 .rs
280 .sp
281 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
282 whitespace is removed, and it is then scanned for \e escapes. Some of these are
283 pretty esoteric features, intended for checking out some of the more
284 complicated features of PCRE. If you are just testing "ordinary" regular
285 expressions, you probably don't need any of these. The following escapes are
286 recognized:
287 .sp
288 \ea alarm (BEL, \ex07)
289 \eb backspace (\ex08)
290 \ee escape (\ex27)
291 \ef formfeed (\ex0c)
292 \en newline (\ex0a)
293 .\" JOIN
294 \eqdd set the PCRE_MATCH_LIMIT limit to dd
295 (any number of digits)
296 \er carriage return (\ex0d)
297 \et tab (\ex09)
298 \ev vertical tab (\ex0b)
299 \ennn octal character (up to 3 octal digits)
300 \exhh hexadecimal character (up to 2 hex digits)
301 .\" JOIN
302 \ex{hh...} hexadecimal character, any number of digits
303 in UTF-8 mode
304 .\" JOIN
305 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
306 or \fBpcre_dfa_exec()\fP
307 .\" JOIN
308 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
309 or \fBpcre_dfa_exec()\fP
310 .\" JOIN
311 \eCdd call pcre_copy_substring() for substring dd
312 after a successful match (number less than 32)
313 .\" JOIN
314 \eCname call pcre_copy_named_substring() for substring
315 "name" after a successful match (name termin-
316 ated by next non alphanumeric character)
317 .\" JOIN
318 \eC+ show the current captured substrings at callout
319 time
320 \eC- do not supply a callout function
321 .\" JOIN
322 \eC!n return 1 instead of 0 when callout number n is
323 reached
324 .\" JOIN
325 \eC!n!m return 1 instead of 0 when callout number n is
326 reached for the nth time
327 .\" JOIN
328 \eC*n pass the number n (may be negative) as callout
329 data; this is used as the callout return value
330 \eD use the \fBpcre_dfa_exec()\fP match function
331 \eF only shortest match for \fBpcre_dfa_exec()\fP
332 .\" JOIN
333 \eGdd call pcre_get_substring() for substring dd
334 after a successful match (number less than 32)
335 .\" JOIN
336 \eGname call pcre_get_named_substring() for substring
337 "name" after a successful match (name termin-
338 ated by next non-alphanumeric character)
339 .\" JOIN
340 \eL call pcre_get_substringlist() after a
341 successful match
342 .\" JOIN
343 \eM discover the minimum MATCH_LIMIT and
345 .\" JOIN
346 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
347 or \fBpcre_dfa_exec()\fP
348 .\" JOIN
349 \eOdd set the size of the output vector passed to
350 \fBpcre_exec()\fP to dd (any number of digits)
351 .\" JOIN
352 \eP pass the PCRE_PARTIAL option to \fBpcre_exec()\fP
353 or \fBpcre_dfa_exec()\fP
354 .\" JOIN
355 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
356 (any number of digits)
357 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
358 \eS output details of memory get/free calls during matching
359 .\" JOIN
360 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
361 or \fBpcre_dfa_exec()\fP
362 .\" JOIN
363 \e? pass the PCRE_NO_UTF8_CHECK option to
364 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
365 \e>dd start the match at offset dd (any number of digits);
366 .\" JOIN
367 this sets the \fIstartoffset\fP argument for \fBpcre_exec()\fP
368 or \fBpcre_dfa_exec()\fP
369 .\" JOIN
370 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
371 or \fBpcre_dfa_exec()\fP
372 .\" JOIN
373 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
374 or \fBpcre_dfa_exec()\fP
375 .\" JOIN
376 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
377 or \fBpcre_dfa_exec()\fP
378 .\" JOIN
379 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
380 or \fBpcre_dfa_exec()\fP
381 .\" JOIN
382 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
383 or \fBpcre_dfa_exec()\fP
384 .sp
385 The escapes that specify line ending sequences are literal strings, exactly as
386 shown. No more than one newline setting should be present in any data line.
387 .P
388 A backslash followed by anything else just escapes the anything else. If
389 the very last character is a backslash, it is ignored. This gives a way of
390 passing an empty line as data, since a real empty line terminates the data
391 input.
392 .P
393 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
394 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
395 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
396 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
397 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
398 place, and checking it out can be instructive. For most simple matches, the
399 number is quite small, but for patterns with very large numbers of matching
400 possibilities, it can become large very quickly with increasing length of
401 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
402 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
403 to complete the match attempt.
404 .P
405 When \eO is used, the value specified may be higher or lower than the size set
406 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
407 the call of \fBpcre_exec()\fP for the line in which it appears.
408 .P
409 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
410 API to be used, the only option-setting sequences that have any effect are \eB
411 and \eZ, causing REG_NOTBOL and REG_NOTEOL, respectively, to be passed to
412 \fBregexec()\fP.
413 .P
414 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
415 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
416 any number of hexadecimal digits inside the braces. The result is from one to
417 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
418 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
419 valid Unicode code points, or indeed valid UTF-8 characters according to the
420 later rules in RFC 3629.
421 .
422 .
424 .rs
425 .sp
426 By default, \fBpcretest\fP uses the standard PCRE matching function,
427 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
428 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
429 different way, and has some restrictions. The differences between the two
430 functions are described in the
431 .\" HREF
432 \fBpcrematching\fP
433 .\"
434 documentation.
435 .P
436 If a data line contains the \eD escape sequence, or if the command line
437 contains the \fB-dfa\fP option, the alternative matching function is called.
438 This function finds all possible matches at a given point. If, however, the \eF
439 escape sequence is present in the data line, it stops after the first match is
440 found. This is always the shortest possible match.
441 .
442 .
444 .rs
445 .sp
446 This section describes the output when the normal matching function,
447 \fBpcre_exec()\fP, is being used.
448 .P
449 When a match succeeds, pcretest outputs the list of captured substrings that
450 \fBpcre_exec()\fP returns, starting with number 0 for the string that matched
451 the whole pattern. Otherwise, it outputs "No match" or "Partial match"
452 when \fBpcre_exec()\fP returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PARTIAL,
453 respectively, and otherwise the PCRE negative error number. Here is an example
454 of an interactive \fBpcretest\fP run.
455 .sp
456 $ pcretest
457 PCRE version 7.0 30-Nov-2006
458 .sp
459 re> /^abc(\ed+)/
460 data> abc123
461 0: abc123
462 1: 123
463 data> xyz
464 No match
465 .sp
466 Note that unset capturing substrings that are not followed by one that is set
467 are not returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In
468 the following example, there are two capturing substrings, but when the first
469 data line is matched, the second, unset substring is not shown. An "internal"
470 unset substring is shown as "<unset>", as for the second data line.
471 .sp
472 re> /(a)|(b)/
473 data> a
474 0: a
475 1: a
476 data> b
477 0: b
478 1: <unset>
479 2: b
480 .sp
481 If the strings contain any non-printing characters, they are output as \e0x
482 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
483 pattern. See below for the definition of non-printing characters. If the
484 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
485 the the rest of the subject string, identified by "0+" like this:
486 .sp
487 re> /cat/+
488 data> cataract
489 0: cat
490 0+ aract
491 .sp
492 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
493 matching attempts are output in sequence, like this:
494 .sp
495 re> /\eBi(\ew\ew)/g
496 data> Mississippi
497 0: iss
498 1: ss
499 0: iss
500 1: ss
501 0: ipp
502 1: pp
503 .sp
504 "No match" is output only if the first match attempt fails.
505 .P
506 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
507 data line that is successfully matched, the substrings extracted by the
508 convenience functions are output with C, G, or L after the string number
509 instead of a colon. This is in addition to the normal full list. The string
510 length (that is, the return from the extraction function) is given in
511 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
512 .P
513 Note that whereas patterns can be continued over several lines (a plain ">"
514 prompt is used for continuations), data lines may not. However newlines can be
515 included in data by means of the \en escape (or \er, \er\en, etc., depending on
516 the newline sequence setting).
517 .
518 .
519 .
521 .rs
522 .sp
523 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
524 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
525 output consists of a list of all the matches that start at the first point in
526 the subject where there is at least one match. For example:
527 .sp
528 re> /(tang|tangerine|tan)/
529 data> yellow tangerine\eD
530 0: tangerine
531 1: tang
532 2: tan
533 .sp
534 (Using the normal matching function on this data finds only "tang".) The
535 longest matching string is always given first (and numbered zero).
536 .P
537 If \fB/g\fP is present on the pattern, the search for further matches resumes
538 at the end of the longest match. For example:
539 .sp
540 re> /(tang|tangerine|tan)/g
541 data> yellow tangerine and tangy sultana\eD
542 0: tangerine
543 1: tang
544 2: tan
545 0: tang
546 1: tan
547 0: tan
548 .sp
549 Since the matching function does not support substring capture, the escape
550 sequences that are concerned with captured substrings are not relevant.
551 .
552 .
554 .rs
555 .sp
556 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
557 indicating that the subject partially matched the pattern, you can restart the
558 match with additional subject data by means of the \eR escape sequence. For
559 example:
560 .sp
561 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
562 data> 23ja\eP\eD
563 Partial match: 23ja
564 data> n05\eR\eD
565 0: n05
566 .sp
567 For further information about partial matching, see the
568 .\" HREF
569 \fBpcrepartial\fP
570 .\"
571 documentation.
572 .
573 .
575 .rs
576 .sp
577 If the pattern contains any callout requests, \fBpcretest\fP's callout function
578 is called during matching. This works with both matching functions. By default,
579 the called function displays the callout number, the start and current
580 positions in the text at the callout time, and the next pattern item to be
581 tested. For example, the output
582 .sp
583 --->pqrabcdef
584 0 ^ ^ \ed
585 .sp
586 indicates that callout number 0 occurred for a match attempt starting at the
587 fourth character of the subject string, when the pointer was at the seventh
588 character of the data, and when the next pattern item was \ed. Just one
589 circumflex is output if the start and current positions are the same.
590 .P
591 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
592 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
593 callout number, the offset in the pattern, preceded by a plus, is output. For
594 example:
595 .sp
596 re> /\ed?[A-E]\e*/C
597 data> E*
598 --->E*
599 +0 ^ \ed?
600 +3 ^ [A-E]
601 +8 ^^ \e*
602 +10 ^ ^
603 0: E*
604 .sp
605 The callout function in \fBpcretest\fP returns zero (carry on matching) by
606 default, but you can use a \eC item in a data line (as described above) to
607 change this.
608 .P
609 Inserting callouts can be helpful when using \fBpcretest\fP to check
610 complicated regular expressions. For further information about callouts, see
611 the
612 .\" HREF
613 \fBpcrecallout\fP
614 .\"
615 documentation.
616 .
617 .
618 .
620 .rs
621 .sp
622 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
623 bytes other than 32-126 are always treated as non-printing characters are are
624 therefore shown as hex escapes.
625 .P
626 When \fBpcretest\fP is outputting text that is a matched part of a subject
627 string, it behaves in the same way, unless a different locale has been set for
628 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
629 function to distinguish printing and non-printing characters.
630 .
631 .
632 .
634 .rs
635 .sp
636 The facilities described in this section are not available when the POSIX
637 inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
638 specified.
639 .P
640 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
641 compiled pattern to a file, by following the modifiers with > and a file name.
642 For example:
643 .sp
644 /pattern/im >/some/file
645 .sp
646 See the
647 .\" HREF
648 \fBpcreprecompile\fP
649 .\"
650 documentation for a discussion about saving and re-using compiled patterns.
651 .P
652 The data that is written is binary. The first eight bytes are the length of the
653 compiled pattern data followed by the length of the optional study data, each
654 written as four bytes in big-endian order (most significant byte first). If
655 there is no study data (either the pattern was not studied, or studying did not
656 return any data), the second length is zero. The lengths are followed by an
657 exact copy of the compiled pattern. If there is additional study data, this
658 follows immediately after the compiled pattern. After writing the file,
659 \fBpcretest\fP expects to read a new pattern.
660 .P
661 A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
662 name instead of a pattern. The name of the file must not contain a < character,
663 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
664 characters.
665 For example:
666 .sp
667 re> </some/file
668 Compiled regex loaded from /some/file
669 No study data
670 .sp
671 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
672 the usual way.
673 .P
674 You can copy a file written by \fBpcretest\fP to a different host and reload it
675 there, even if the new host has opposite endianness to the one on which the
676 pattern was compiled. For example, you can compile on an i86 machine and run on
677 a SPARC machine.
678 .P
679 File names for saving and reloading can be absolute or relative, but note that
680 the shell facility of expanding a file name that starts with a tilde (~) is not
681 available.
682 .P
683 The ability to save and reload files in \fBpcretest\fP is intended for testing
684 and experimentation. It is not intended for production use because only a
685 single pattern can be written to a file. Furthermore, there is no facility for
686 supplying custom character tables for use with a reloaded pattern. If the
687 original pattern was compiled with custom tables, an attempt to match a subject
688 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
689 Finally, if you attempt to load a file that is not in the correct format, the
690 result is undefined.
691 .
692 .
693 .SH "SEE ALSO"
694 .rs
695 .sp
696 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
697 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
698 .
699 .
701 .rs
702 .sp
703 .nf
704 Philip Hazel
705 University Computing Service
706 Cambridge CB2 3QH, England.
707 .fi
708 .
709 .
711 .rs
712 .sp
713 .nf
714 Last updated: 19 November 2007
715 Copyright (c) 1997-2007 University of Cambridge.
716 .fi


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