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1 .TH PCRETEST 1
2 .SH NAME
3 pcretest - a program for testing Perl-compatible regular expressions.
4 .SH SYNOPSIS
5 .rs
6 .sp
7 .B pcretest "[options] [input file [output file]]"
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. The input for \fBpcretest\fP is a sequence of regular expression
22 patterns and strings to be matched, as described below. The output shows the
23 result of each match. Options on the command line and the patterns control PCRE
24 options and exactly what is output.
25 .
26 .
27 .SH COMMAND LINE OPTIONS
28 .rs
29 .TP 10
30 \fB-b\fP
31 Behave as if each pattern has the \fB/B\fP (show byte code) modifier; the
32 internal form is output after compilation.
33 .TP 10
34 \fB-C\fP
35 Output the version number of the PCRE library, and all available information
36 about the optional features that are included, and then exit.
37 .TP 10
38 \fB-d\fP
39 Behave as if each pattern has the \fB/D\fP (debug) modifier; the internal
40 form and information about the compiled pattern is output after compilation;
41 \fB-d\fP is equivalent to \fB-b -i\fP.
42 .TP 10
43 \fB-dfa\fP
44 Behave as if each data line contains the \eD escape sequence; this causes the
45 alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
46 standard \fBpcre_exec()\fP function (more detail is given below).
47 .TP 10
48 \fB-help\fP
49 Output a brief summary these options and then exit.
50 .TP 10
51 \fB-i\fP
52 Behave as if each pattern has the \fB/I\fP modifier; information about the
53 compiled pattern is given after compilation.
54 .TP 10
55 \fB-M\fP
56 Behave as if each data line contains the \eM escape sequence; this causes
57 PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by
58 calling \fBpcre_exec()\fP repeatedly with different limits.
59 .TP 10
60 \fB-m\fP
61 Output the size of each compiled pattern after it has been compiled. This is
62 equivalent to adding \fB/M\fP to each regular expression.
63 .TP 10
64 \fB-o\fP \fIosize\fP
65 Set the number of elements in the output vector that is used when calling
66 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
67 is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
68 22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
69 changed for individual matching calls by including \eO in the data line (see
70 below).
71 .TP 10
72 \fB-p\fP
73 Behave as if each pattern has the \fB/P\fP modifier; the POSIX wrapper API is
74 used to call PCRE. None of the other options has any effect when \fB-p\fP is
75 set.
76 .TP 10
77 \fB-q\fP
78 Do not output the version number of \fBpcretest\fP at the start of execution.
79 .TP 10
80 \fB-S\fP \fIsize\fP
81 On Unix-like systems, set the size of the run-time stack to \fIsize\fP
82 megabytes.
83 .TP 10
84 \fB-s\fP
85 Behave as if each pattern has the \fB/S\fP modifier; in other words, force each
86 pattern to be studied. If the \fB/I\fP or \fB/D\fP option is present on a
87 pattern (requesting output about the compiled pattern), information about the
88 result of studying is not included when studying is caused only by \fB-s\fP and
89 neither \fB-i\fP nor \fB-d\fP is present on the command line. This behaviour
90 means that the output from tests that are run with and without \fB-s\fP should
91 be identical, except when options that output information about the actual
92 running of a match are set. The \fB-M\fP, \fB-t\fP, and \fB-tm\fP options,
93 which give information about resources used, are likely to produce different
94 output with and without \fB-s\fP. Output may also differ if the \fB/C\fP option
95 is present on an individual pattern. This uses callouts to trace the the
96 matching process, and this may be different between studied and non-studied
97 patterns. If the pattern contains (*MARK) items there may also be differences,
98 for the same reason. The \fB-s\fP command line option can be overridden for
99 specific patterns that should never be studied (see the /S option below).
100 .TP 10
101 \fB-t\fP
102 Run each compile, study, and match many times with a timer, and output
103 resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
104 \fB-t\fP, because you will then get the size output a zillion times, and the
105 timing will be distorted. You can control the number of iterations that are
106 used for timing by following \fB-t\fP with a number (as a separate item on the
107 command line). For example, "-t 1000" would iterate 1000 times. The default is
108 to iterate 500000 times.
109 .TP 10
110 \fB-tm\fP
111 This is like \fB-t\fP except that it times only the matching phase, not the
112 compile or study phases.
113 .
114 .
115 .SH DESCRIPTION
116 .rs
117 .sp
118 If \fBpcretest\fP is given two filename arguments, it reads from the first and
119 writes to the second. If it is given only one filename argument, it reads from
120 that file and writes to stdout. Otherwise, it reads from stdin and writes to
121 stdout, and prompts for each line of input, using "re>" to prompt for regular
122 expressions, and "data>" to prompt for data lines.
123 .P
124 When \fBpcretest\fP is built, a configuration option can specify that it should
125 be linked with the \fBlibreadline\fP library. When this is done, if the input
126 is from a terminal, it is read using the \fBreadline()\fP function. This
127 provides line-editing and history facilities. The output from the \fB-help\fP
128 option states whether or not \fBreadline()\fP will be used.
129 .P
130 The program handles any number of sets of input on a single input file. Each
131 set starts with a regular expression, and continues with any number of data
132 lines to be matched against the pattern.
133 .P
134 Each data line is matched separately and independently. If you want to do
135 multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
136 etc., depending on the newline setting) in a single line of input to encode the
137 newline sequences. There is no limit on the length of data lines; the input
138 buffer is automatically extended if it is too small.
139 .P
140 An empty line signals the end of the data lines, at which point a new regular
141 expression is read. The regular expressions are given enclosed in any
142 non-alphanumeric delimiters other than backslash, for example:
143 .sp
144 /(a|bc)x+yz/
145 .sp
146 White space before the initial delimiter is ignored. A regular expression may
147 be continued over several input lines, in which case the newline characters are
148 included within it. It is possible to include the delimiter within the pattern
149 by escaping it, for example
150 .sp
151 /abc\e/def/
152 .sp
153 If you do so, the escape and the delimiter form part of the pattern, but since
154 delimiters are always non-alphanumeric, this does not affect its interpretation.
155 If the terminating delimiter is immediately followed by a backslash, for
156 example,
157 .sp
158 /abc/\e
159 .sp
160 then a backslash is added to the end of the pattern. This is done to provide a
161 way of testing the error condition that arises if a pattern finishes with a
162 backslash, because
163 .sp
164 /abc\e/
165 .sp
166 is interpreted as the first line of a pattern that starts with "abc/", causing
167 pcretest to read the next line as a continuation of the regular expression.
168 .
169 .
170 .SH "PATTERN MODIFIERS"
171 .rs
172 .sp
173 A pattern may be followed by any number of modifiers, which are mostly single
174 characters. Following Perl usage, these are referred to below as, for example,
175 "the \fB/i\fP modifier", even though the delimiter of the pattern need not
176 always be a slash, and no slash is used when writing modifiers. White space may
177 appear between the final pattern delimiter and the first modifier, and between
178 the modifiers themselves.
179 .P
180 The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
181 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
182 \fBpcre_compile()\fP is called. These four modifier letters have the same
183 effect as they do in Perl. For example:
184 .sp
185 /caseless/i
186 .sp
187 The following table shows additional modifiers for setting PCRE compile-time
188 options that do not correspond to anything in Perl:
189 .sp
190 \fB/8\fP PCRE_UTF8
191 \fB/?\fP PCRE_NO_UTF8_CHECK
192 \fB/A\fP PCRE_ANCHORED
193 \fB/C\fP PCRE_AUTO_CALLOUT
194 \fB/E\fP PCRE_DOLLAR_ENDONLY
195 \fB/f\fP PCRE_FIRSTLINE
196 \fB/J\fP PCRE_DUPNAMES
197 \fB/N\fP PCRE_NO_AUTO_CAPTURE
198 \fB/U\fP PCRE_UNGREEDY
199 \fB/W\fP PCRE_UCP
200 \fB/X\fP PCRE_EXTRA
201 \fB/Y\fP PCRE_NO_START_OPTIMIZE
202 \fB/<JS>\fP PCRE_JAVASCRIPT_COMPAT
203 \fB/<cr>\fP PCRE_NEWLINE_CR
204 \fB/<lf>\fP PCRE_NEWLINE_LF
205 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
206 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
207 \fB/<any>\fP PCRE_NEWLINE_ANY
208 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
209 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
210 .sp
211 The modifiers that are enclosed in angle brackets are literal strings as shown,
212 including the angle brackets, but the letters within can be in either case.
213 This example sets multiline matching with CRLF as the line ending sequence:
214 .sp
215 /^abc/m<CRLF>
216 .sp
217 As well as turning on the PCRE_UTF8 option, the \fB/8\fP modifier also causes
218 any non-printing characters in output strings to be printed using the
219 \ex{hh...} notation if they are valid UTF-8 sequences. Full details of the PCRE
220 options are given in the
221 .\" HREF
222 \fBpcreapi\fP
223 .\"
224 documentation.
225 .
226 .
227 .SS "Finding all matches in a string"
228 .rs
229 .sp
230 Searching for all possible matches within each subject string can be requested
231 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
232 again to search the remainder of the subject string. The difference between
233 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
234 \fBpcre_exec()\fP to start searching at a new point within the entire string
235 (which is in effect what Perl does), whereas the latter passes over a shortened
236 substring. This makes a difference to the matching process if the pattern
237 begins with a lookbehind assertion (including \eb or \eB).
238 .P
239 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
240 empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and
241 PCRE_ANCHORED flags set in order to search for another, non-empty, match at the
242 same point. If this second match fails, the start offset is advanced, and the
243 normal match is retried. This imitates the way Perl handles such cases when
244 using the \fB/g\fP modifier or the \fBsplit()\fP function. Normally, the start
245 offset is advanced by one character, but if the newline convention recognizes
246 CRLF as a newline, and the current character is CR followed by LF, an advance
247 of two is used.
248 .
249 .
250 .SS "Other modifiers"
251 .rs
252 .sp
253 There are yet more modifiers for controlling the way \fBpcretest\fP
254 operates.
255 .P
256 The \fB/+\fP modifier requests that as well as outputting the substring that
257 matched the entire pattern, \fBpcretest\fP should in addition output the
258 remainder of the subject string. This is useful for tests where the subject
259 contains multiple copies of the same substring. If the \fB+\fP modifier appears
260 twice, the same action is taken for captured substrings. In each case the
261 remainder is output on the following line with a plus character following the
262 capture number.
263 .P
264 The \fB/=\fP modifier requests that the values of all potential captured
265 parentheses be output after a match by \fBpcre_exec()\fP. By default, only
266 those up to the highest one actually used in the match are output
267 (corresponding to the return code from \fBpcre_exec()\fP). Values in the
268 offsets vector corresponding to higher numbers should be set to -1, and these
269 are output as "<unset>". This modifier gives a way of checking that this is
270 happening.
271 .P
272 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
273 output a representation of the compiled byte code after compilation. Normally
274 this information contains length and offset values; however, if \fB/Z\fP is
275 also present, this data is replaced by spaces. This is a special feature for
276 use in the automatic test scripts; it ensures that the same output is generated
277 for different internal link sizes.
278 .P
279 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
280 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
281 .P
282 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
283 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
284 facility is for testing the feature in PCRE that allows it to execute patterns
285 that were compiled on a host with a different endianness. This feature is not
286 available when the POSIX interface to PCRE is being used, that is, when the
287 \fB/P\fP pattern modifier is specified. See also the section about saving and
288 reloading compiled patterns below.
289 .P
290 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
291 compiled pattern (whether it is anchored, has a fixed first character, and
292 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
293 pattern. If the pattern is studied, the results of that are also output.
294 .P
295 The \fB/K\fP modifier requests \fBpcretest\fP to show names from backtracking
296 control verbs that are returned from calls to \fBpcre_exec()\fP. It causes
297 \fBpcretest\fP to create a \fBpcre_extra\fP block if one has not already been
298 created by a call to \fBpcre_study()\fP, and to set the PCRE_EXTRA_MARK flag
299 and the \fBmark\fP field within it, every time that \fBpcre_exec()\fP is
300 called. If the variable that the \fBmark\fP field points to is non-NULL for a
301 match, non-match, or partial match, \fBpcretest\fP prints the string to which
302 it points. For a match, this is shown on a line by itself, tagged with "MK:".
303 For a non-match it is added to the message.
304 .P
305 The \fB/L\fP modifier must be followed directly by the name of a locale, for
306 example,
307 .sp
308 /pattern/Lfr_FR
309 .sp
310 For this reason, it must be the last modifier. The given locale is set,
311 \fBpcre_maketables()\fP is called to build a set of character tables for the
312 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
313 regular expression. Without an \fB/L\fP (or \fB/T\fP) modifier, NULL is passed
314 as the tables pointer; that is, \fB/L\fP applies only to the expression on
315 which it appears.
316 .P
317 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
318 pattern to be output.
319 .P
320 If the \fB/S\fP modifier appears once, it causes \fBpcre_study()\fP to be
321 called after the expression has been compiled, and the results used when the
322 expression is matched. If \fB/S\fP appears twice, it suppresses studying, even
323 if it was requested externally by the \fB-s\fP command line option. This makes
324 it possible to specify that certain patterns are always studied, and others are
325 never studied, independently of \fB-s\fP. This feature is used in the test
326 files in a few cases where the output is different when the pattern is studied.
327 .P
328 The \fB/T\fP modifier must be followed by a single digit. It causes a specific
329 set of built-in character tables to be passed to \fBpcre_compile()\fP. It is
330 used in the standard PCRE tests to check behaviour with different character
331 tables. The digit specifies the tables as follows:
332 .sp
333 0 the default ASCII tables, as distributed in
334 pcre_chartables.c.dist
335 1 a set of tables defining ISO 8859 characters
336 .sp
337 In table 1, some characters whose codes are greater than 128 are identified as
338 letters, digits, spaces, etc.
339 .
340 .
341 .SS "Using the POSIX wrapper API"
342 .rs
343 .sp
344 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
345 API rather than its native API. When \fB/P\fP is set, the following modifiers
346 set options for the \fBregcomp()\fP function:
347 .sp
348 /i REG_ICASE
349 /m REG_NEWLINE
350 /N REG_NOSUB
351 /s REG_DOTALL )
352 /U REG_UNGREEDY ) These options are not part of
353 /W REG_UCP ) the POSIX standard
354 /8 REG_UTF8 )
355 .sp
356 The \fB/+\fP modifier works as described above. All other modifiers are
357 ignored.
358 .
359 .
360 .SH "DATA LINES"
361 .rs
362 .sp
363 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
364 white space is removed, and it is then scanned for \e escapes. Some of these
365 are pretty esoteric features, intended for checking out some of the more
366 complicated features of PCRE. If you are just testing "ordinary" regular
367 expressions, you probably don't need any of these. The following escapes are
368 recognized:
369 .sp
370 \ea alarm (BEL, \ex07)
371 \eb backspace (\ex08)
372 \ee escape (\ex27)
373 \ef form feed (\ex0c)
374 \en newline (\ex0a)
375 .\" JOIN
376 \eqdd set the PCRE_MATCH_LIMIT limit to dd
377 (any number of digits)
378 \er carriage return (\ex0d)
379 \et tab (\ex09)
380 \ev vertical tab (\ex0b)
381 \ennn octal character (up to 3 octal digits)
382 always a byte unless > 255 in UTF-8 mode
383 \exhh hexadecimal byte (up to 2 hex digits)
384 .\" JOIN
385 \ex{hh...} hexadecimal character, any number of digits
386 in UTF-8 mode
387 .\" JOIN
388 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
389 or \fBpcre_dfa_exec()\fP
390 .\" JOIN
391 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
392 or \fBpcre_dfa_exec()\fP
393 .\" JOIN
394 \eCdd call pcre_copy_substring() for substring dd
395 after a successful match (number less than 32)
396 .\" JOIN
397 \eCname call pcre_copy_named_substring() for substring
398 "name" after a successful match (name termin-
399 ated by next non alphanumeric character)
400 .\" JOIN
401 \eC+ show the current captured substrings at callout
402 time
403 \eC- do not supply a callout function
404 .\" JOIN
405 \eC!n return 1 instead of 0 when callout number n is
406 reached
407 .\" JOIN
408 \eC!n!m return 1 instead of 0 when callout number n is
409 reached for the nth time
410 .\" JOIN
411 \eC*n pass the number n (may be negative) as callout
412 data; this is used as the callout return value
413 \eD use the \fBpcre_dfa_exec()\fP match function
414 \eF only shortest match for \fBpcre_dfa_exec()\fP
415 .\" JOIN
416 \eGdd call pcre_get_substring() for substring dd
417 after a successful match (number less than 32)
418 .\" JOIN
419 \eGname call pcre_get_named_substring() for substring
420 "name" after a successful match (name termin-
421 ated by next non-alphanumeric character)
422 .\" JOIN
423 \eL call pcre_get_substringlist() after a
424 successful match
425 .\" JOIN
426 \eM discover the minimum MATCH_LIMIT and
427 MATCH_LIMIT_RECURSION settings
428 .\" JOIN
429 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
430 or \fBpcre_dfa_exec()\fP; if used twice, pass the
431 PCRE_NOTEMPTY_ATSTART option
432 .\" JOIN
433 \eOdd set the size of the output vector passed to
434 \fBpcre_exec()\fP to dd (any number of digits)
435 .\" JOIN
436 \eP pass the PCRE_PARTIAL_SOFT option to \fBpcre_exec()\fP
437 or \fBpcre_dfa_exec()\fP; if used twice, pass the
438 PCRE_PARTIAL_HARD option
439 .\" JOIN
440 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
441 (any number of digits)
442 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
443 \eS output details of memory get/free calls during matching
444 .\" JOIN
445 \eY pass the PCRE_NO_START_OPTIMIZE option to \fBpcre_exec()\fP
446 or \fBpcre_dfa_exec()\fP
447 .\" JOIN
448 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
449 or \fBpcre_dfa_exec()\fP
450 .\" JOIN
451 \e? pass the PCRE_NO_UTF8_CHECK option to
452 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
453 .\" JOIN
454 \e>dd start the match at offset dd (optional "-"; then
455 any number of digits); this sets the \fIstartoffset\fP
456 argument for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
457 .\" JOIN
458 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
459 or \fBpcre_dfa_exec()\fP
460 .\" JOIN
461 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
462 or \fBpcre_dfa_exec()\fP
463 .\" JOIN
464 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
465 or \fBpcre_dfa_exec()\fP
466 .\" JOIN
467 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
468 or \fBpcre_dfa_exec()\fP
469 .\" JOIN
470 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
471 or \fBpcre_dfa_exec()\fP
472 .sp
473 Note that \exhh always specifies one byte, even in UTF-8 mode; this makes it
474 possible to construct invalid UTF-8 sequences for testing purposes. On the
475 other hand, \ex{hh} is interpreted as a UTF-8 character in UTF-8 mode,
476 generating more than one byte if the value is greater than 127. When not in
477 UTF-8 mode, it generates one byte for values less than 256, and causes an error
478 for greater values.
479 .P
480 The escapes that specify line ending sequences are literal strings, exactly as
481 shown. No more than one newline setting should be present in any data line.
482 .P
483 A backslash followed by anything else just escapes the anything else. If
484 the very last character is a backslash, it is ignored. This gives a way of
485 passing an empty line as data, since a real empty line terminates the data
486 input.
487 .P
488 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
489 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
490 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
491 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
492 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
493 place, and checking it out can be instructive. For most simple matches, the
494 number is quite small, but for patterns with very large numbers of matching
495 possibilities, it can become large very quickly with increasing length of
496 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
497 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
498 to complete the match attempt.
499 .P
500 When \eO is used, the value specified may be higher or lower than the size set
501 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
502 the call of \fBpcre_exec()\fP for the line in which it appears.
503 .P
504 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
505 API to be used, the only option-setting sequences that have any effect are \eB,
506 \eN, and \eZ, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively,
507 to be passed to \fBregexec()\fP.
508 .P
509 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
510 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
511 any number of hexadecimal digits inside the braces. The result is from one to
512 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
513 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
514 valid Unicode code points, or indeed valid UTF-8 characters according to the
515 later rules in RFC 3629.
516 .
517 .
518 .SH "THE ALTERNATIVE MATCHING FUNCTION"
519 .rs
520 .sp
521 By default, \fBpcretest\fP uses the standard PCRE matching function,
522 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
523 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
524 different way, and has some restrictions. The differences between the two
525 functions are described in the
526 .\" HREF
527 \fBpcrematching\fP
528 .\"
529 documentation.
530 .P
531 If a data line contains the \eD escape sequence, or if the command line
532 contains the \fB-dfa\fP option, the alternative matching function is called.
533 This function finds all possible matches at a given point. If, however, the \eF
534 escape sequence is present in the data line, it stops after the first match is
535 found. This is always the shortest possible match.
536 .
537 .
538 .SH "DEFAULT OUTPUT FROM PCRETEST"
539 .rs
540 .sp
541 This section describes the output when the normal matching function,
542 \fBpcre_exec()\fP, is being used.
543 .P
544 When a match succeeds, \fBpcretest\fP outputs the list of captured substrings
545 that \fBpcre_exec()\fP returns, starting with number 0 for the string that
546 matched the whole pattern. Otherwise, it outputs "No match" when the return is
547 PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching
548 substring when \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL. (Note that this is
549 the entire substring that was inspected during the partial match; it may
550 include characters before the actual match start if a lookbehind assertion,
551 \eK, \eb, or \eB was involved.) For any other return, \fBpcretest\fP outputs
552 the PCRE negative error number and a short descriptive phrase. If the error is
553 a failed UTF-8 string check, the byte offset of the start of the failing
554 character and the reason code are also output, provided that the size of the
555 output vector is at least two. Here is an example of an interactive
556 \fBpcretest\fP run.
557 .sp
558 $ pcretest
559 PCRE version 8.13 2011-04-30
560 .sp
561 re> /^abc(\ed+)/
562 data> abc123
563 0: abc123
564 1: 123
565 data> xyz
566 No match
567 .sp
568 Unset capturing substrings that are not followed by one that is set are not
569 returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In the
570 following example, there are two capturing substrings, but when the first data
571 line is matched, the second, unset substring is not shown. An "internal" unset
572 substring is shown as "<unset>", as for the second data line.
573 .sp
574 re> /(a)|(b)/
575 data> a
576 0: a
577 1: a
578 data> b
579 0: b
580 1: <unset>
581 2: b
582 .sp
583 If the strings contain any non-printing characters, they are output as \e0x
584 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
585 pattern. See below for the definition of non-printing characters. If the
586 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
587 the the rest of the subject string, identified by "0+" like this:
588 .sp
589 re> /cat/+
590 data> cataract
591 0: cat
592 0+ aract
593 .sp
594 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
595 matching attempts are output in sequence, like this:
596 .sp
597 re> /\eBi(\ew\ew)/g
598 data> Mississippi
599 0: iss
600 1: ss
601 0: iss
602 1: ss
603 0: ipp
604 1: pp
605 .sp
606 "No match" is output only if the first match attempt fails. Here is an example
607 of a failure message (the offset 4 that is specified by \e>4 is past the end of
608 the subject string):
609 .sp
610 re> /xyz/
611 data> xyz\e>4
612 Error -24 (bad offset value)
613 .P
614 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
615 data line that is successfully matched, the substrings extracted by the
616 convenience functions are output with C, G, or L after the string number
617 instead of a colon. This is in addition to the normal full list. The string
618 length (that is, the return from the extraction function) is given in
619 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
620 .P
621 Note that whereas patterns can be continued over several lines (a plain ">"
622 prompt is used for continuations), data lines may not. However newlines can be
623 included in data by means of the \en escape (or \er, \er\en, etc., depending on
624 the newline sequence setting).
625 .
626 .
627 .
628 .SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
629 .rs
630 .sp
631 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
632 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
633 output consists of a list of all the matches that start at the first point in
634 the subject where there is at least one match. For example:
635 .sp
636 re> /(tang|tangerine|tan)/
637 data> yellow tangerine\eD
638 0: tangerine
639 1: tang
640 2: tan
641 .sp
642 (Using the normal matching function on this data finds only "tang".) The
643 longest matching string is always given first (and numbered zero). After a
644 PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the
645 partially matching substring. (Note that this is the entire substring that was
646 inspected during the partial match; it may include characters before the actual
647 match start if a lookbehind assertion, \eK, \eb, or \eB was involved.)
648 .P
649 If \fB/g\fP is present on the pattern, the search for further matches resumes
650 at the end of the longest match. For example:
651 .sp
652 re> /(tang|tangerine|tan)/g
653 data> yellow tangerine and tangy sultana\eD
654 0: tangerine
655 1: tang
656 2: tan
657 0: tang
658 1: tan
659 0: tan
660 .sp
661 Since the matching function does not support substring capture, the escape
662 sequences that are concerned with captured substrings are not relevant.
663 .
664 .
665 .SH "RESTARTING AFTER A PARTIAL MATCH"
666 .rs
667 .sp
668 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
669 indicating that the subject partially matched the pattern, you can restart the
670 match with additional subject data by means of the \eR escape sequence. For
671 example:
672 .sp
673 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
674 data> 23ja\eP\eD
675 Partial match: 23ja
676 data> n05\eR\eD
677 0: n05
678 .sp
679 For further information about partial matching, see the
680 .\" HREF
681 \fBpcrepartial\fP
682 .\"
683 documentation.
684 .
685 .
686 .SH CALLOUTS
687 .rs
688 .sp
689 If the pattern contains any callout requests, \fBpcretest\fP's callout function
690 is called during matching. This works with both matching functions. By default,
691 the called function displays the callout number, the start and current
692 positions in the text at the callout time, and the next pattern item to be
693 tested. For example, the output
694 .sp
695 --->pqrabcdef
696 0 ^ ^ \ed
697 .sp
698 indicates that callout number 0 occurred for a match attempt starting at the
699 fourth character of the subject string, when the pointer was at the seventh
700 character of the data, and when the next pattern item was \ed. Just one
701 circumflex is output if the start and current positions are the same.
702 .P
703 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
704 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
705 callout number, the offset in the pattern, preceded by a plus, is output. For
706 example:
707 .sp
708 re> /\ed?[A-E]\e*/C
709 data> E*
710 --->E*
711 +0 ^ \ed?
712 +3 ^ [A-E]
713 +8 ^^ \e*
714 +10 ^ ^
715 0: E*
716 .sp
717 If a pattern contains (*MARK) items, an additional line is output whenever
718 a change of latest mark is passed to the callout function. For example:
719 .sp
720 re> /a(*MARK:X)bc/C
721 data> abc
722 --->abc
723 +0 ^ a
724 +1 ^^ (*MARK:X)
725 +10 ^^ b
726 Latest Mark: X
727 +11 ^ ^ c
728 +12 ^ ^
729 0: abc
730 .sp
731 The mark changes between matching "a" and "b", but stays the same for the rest
732 of the match, so nothing more is output. If, as a result of backtracking, the
733 mark reverts to being unset, the text "<unset>" is output.
734 .P
735 The callout function in \fBpcretest\fP returns zero (carry on matching) by
736 default, but you can use a \eC item in a data line (as described above) to
737 change this and other parameters of the callout.
738 .P
739 Inserting callouts can be helpful when using \fBpcretest\fP to check
740 complicated regular expressions. For further information about callouts, see
741 the
742 .\" HREF
743 \fBpcrecallout\fP
744 .\"
745 documentation.
746 .
747 .
748 .
749 .SH "NON-PRINTING CHARACTERS"
750 .rs
751 .sp
752 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
753 bytes other than 32-126 are always treated as non-printing characters are are
754 therefore shown as hex escapes.
755 .P
756 When \fBpcretest\fP is outputting text that is a matched part of a subject
757 string, it behaves in the same way, unless a different locale has been set for
758 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
759 function to distinguish printing and non-printing characters.
760 .
761 .
762 .
763 .SH "SAVING AND RELOADING COMPILED PATTERNS"
764 .rs
765 .sp
766 The facilities described in this section are not available when the POSIX
767 interface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
768 specified.
769 .P
770 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
771 compiled pattern to a file, by following the modifiers with > and a file name.
772 For example:
773 .sp
774 /pattern/im >/some/file
775 .sp
776 See the
777 .\" HREF
778 \fBpcreprecompile\fP
779 .\"
780 documentation for a discussion about saving and re-using compiled patterns.
781 .P
782 The data that is written is binary. The first eight bytes are the length of the
783 compiled pattern data followed by the length of the optional study data, each
784 written as four bytes in big-endian order (most significant byte first). If
785 there is no study data (either the pattern was not studied, or studying did not
786 return any data), the second length is zero. The lengths are followed by an
787 exact copy of the compiled pattern. If there is additional study data, this
788 follows immediately after the compiled pattern. After writing the file,
789 \fBpcretest\fP expects to read a new pattern.
790 .P
791 A saved pattern can be reloaded into \fBpcretest\fP by specifying < and a file
792 name instead of a pattern. The name of the file must not contain a < character,
793 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
794 characters.
795 For example:
796 .sp
797 re> </some/file
798 Compiled pattern loaded from /some/file
799 No study data
800 .sp
801 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
802 the usual way.
803 .P
804 You can copy a file written by \fBpcretest\fP to a different host and reload it
805 there, even if the new host has opposite endianness to the one on which the
806 pattern was compiled. For example, you can compile on an i86 machine and run on
807 a SPARC machine.
808 .P
809 File names for saving and reloading can be absolute or relative, but note that
810 the shell facility of expanding a file name that starts with a tilde (~) is not
811 available.
812 .P
813 The ability to save and reload files in \fBpcretest\fP is intended for testing
814 and experimentation. It is not intended for production use because only a
815 single pattern can be written to a file. Furthermore, there is no facility for
816 supplying custom character tables for use with a reloaded pattern. If the
817 original pattern was compiled with custom tables, an attempt to match a subject
818 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
819 Finally, if you attempt to load a file that is not in the correct format, the
820 result is undefined.
821 .
822 .
823 .SH "SEE ALSO"
824 .rs
825 .sp
826 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
827 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
828 .
829 .
830 .SH AUTHOR
831 .rs
832 .sp
833 .nf
834 Philip Hazel
835 University Computing Service
836 Cambridge CB2 3QH, England.
837 .fi
838 .
839 .
840 .SH REVISION
841 .rs
842 .sp
843 .nf
844 Last updated: 01 August 2011
845 Copyright (c) 1997-2011 University of Cambridge.
846 .fi

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