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1 <html>
2 <head>
3 <title>pcrecpp specification</title>
4 </head>
5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 <h1>pcrecpp man page</h1>
7 <p>
8 Return to the <a href="index.html">PCRE index page</a>.
9 </p>
10 <p>
11 This page is part of the PCRE HTML documentation. It was generated automatically
12 from the original man page. If there is any nonsense in it, please consult the
13 man page, in case the conversion went wrong.
14 <br>
15 <ul>
16 <li><a name="TOC1" href="#SEC1">SYNOPSIS OF C++ WRAPPER</a>
17 <li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
18 <li><a name="TOC3" href="#SEC3">MATCHING INTERFACE</a>
19 <li><a name="TOC4" href="#SEC4">QUOTING METACHARACTERS</a>
20 <li><a name="TOC5" href="#SEC5">PARTIAL MATCHES</a>
21 <li><a name="TOC6" href="#SEC6">UTF-8 AND THE MATCHING INTERFACE</a>
23 <li><a name="TOC8" href="#SEC8">SCANNING TEXT INCREMENTALLY</a>
24 <li><a name="TOC9" href="#SEC9">PARSING HEX/OCTAL/C-RADIX NUMBERS</a>
25 <li><a name="TOC10" href="#SEC10">REPLACING PARTS OF STRINGS</a>
26 <li><a name="TOC11" href="#SEC11">AUTHOR</a>
27 <li><a name="TOC12" href="#SEC12">REVISION</a>
28 </ul>
29 <br><a name="SEC1" href="#TOC1">SYNOPSIS OF C++ WRAPPER</a><br>
30 <P>
31 <b>#include &#60;pcrecpp.h&#62;</b>
32 </P>
33 <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
34 <P>
35 The C++ wrapper for PCRE was provided by Google Inc. Some additional
36 functionality was added by Giuseppe Maxia. This brief man page was constructed
37 from the notes in the <i>pcrecpp.h</i> file, which should be consulted for
38 further details. Note that the C++ wrapper supports only the original 8-bit
39 PCRE library. There is no 16-bit or 32-bit support at present.
40 </P>
41 <br><a name="SEC3" href="#TOC1">MATCHING INTERFACE</a><br>
42 <P>
43 The "FullMatch" operation checks that supplied text matches a supplied pattern
44 exactly. If pointer arguments are supplied, it copies matched sub-strings that
45 match sub-patterns into them.
46 <pre>
47 Example: successful match
48 pcrecpp::RE re("h.*o");
49 re.FullMatch("hello");
51 Example: unsuccessful match (requires full match):
52 pcrecpp::RE re("e");
53 !re.FullMatch("hello");
55 Example: creating a temporary RE object:
56 pcrecpp::RE("h.*o").FullMatch("hello");
57 </pre>
58 You can pass in a "const char*" or a "string" for "text". The examples below
59 tend to use a const char*. You can, as in the different examples above, store
60 the RE object explicitly in a variable or use a temporary RE object. The
61 examples below use one mode or the other arbitrarily. Either could correctly be
62 used for any of these examples.
63 </P>
64 <P>
65 You must supply extra pointer arguments to extract matched subpieces.
66 <pre>
67 Example: extracts "ruby" into "s" and 1234 into "i"
68 int i;
69 string s;
70 pcrecpp::RE re("(\\w+):(\\d+)");
71 re.FullMatch("ruby:1234", &s, &i);
73 Example: does not try to extract any extra sub-patterns
74 re.FullMatch("ruby:1234", &s);
76 Example: does not try to extract into NULL
77 re.FullMatch("ruby:1234", NULL, &i);
79 Example: integer overflow causes failure
80 !re.FullMatch("ruby:1234567891234", NULL, &i);
82 Example: fails because there aren't enough sub-patterns:
83 !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
85 Example: fails because string cannot be stored in integer
86 !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
87 </pre>
88 The provided pointer arguments can be pointers to any scalar numeric
89 type, or one of:
90 <pre>
91 string (matched piece is copied to string)
92 StringPiece (StringPiece is mutated to point to matched piece)
93 T (where "bool T::ParseFrom(const char*, int)" exists)
94 NULL (the corresponding matched sub-pattern is not copied)
95 </pre>
96 The function returns true iff all of the following conditions are satisfied:
97 <pre>
98 a. "text" matches "pattern" exactly;
100 b. The number of matched sub-patterns is &#62;= number of supplied
101 pointers;
103 c. The "i"th argument has a suitable type for holding the
104 string captured as the "i"th sub-pattern. If you pass in
105 void * NULL for the "i"th argument, or a non-void * NULL
106 of the correct type, or pass fewer arguments than the
107 number of sub-patterns, "i"th captured sub-pattern is
108 ignored.
109 </pre>
110 CAVEAT: An optional sub-pattern that does not exist in the matched
111 string is assigned the empty string. Therefore, the following will
112 return false (because the empty string is not a valid number):
113 <pre>
114 int number;
115 pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
116 </pre>
117 The matching interface supports at most 16 arguments per call.
118 If you need more, consider using the more general interface
119 <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
120 <b>DoMatch</b>.
121 </P>
122 <P>
123 NOTE: Do not use <b>no_arg</b>, which is used internally to mark the end of a
124 list of optional arguments, as a placeholder for missing arguments, as this can
125 lead to segfaults.
126 </P>
127 <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
128 <P>
129 You can use the "QuoteMeta" operation to insert backslashes before all
130 potentially meaningful characters in a string. The returned string, used as a
131 regular expression, will exactly match the original string.
132 <pre>
133 Example:
134 string quoted = RE::QuoteMeta(unquoted);
135 </pre>
136 Note that it's legal to escape a character even if it has no special meaning in
137 a regular expression -- so this function does that. (This also makes it
138 identical to the perl function of the same name; see "perldoc -f quotemeta".)
139 For example, "1.5-2.0?" becomes "1\.5\-2\.0\?".
140 </P>
141 <br><a name="SEC5" href="#TOC1">PARTIAL MATCHES</a><br>
142 <P>
143 You can use the "PartialMatch" operation when you want the pattern
144 to match any substring of the text.
145 <pre>
146 Example: simple search for a string:
147 pcrecpp::RE("ell").PartialMatch("hello");
149 Example: find first number in a string:
150 int number;
151 pcrecpp::RE re("(\\d+)");
152 re.PartialMatch("x*100 + 20", &number);
153 assert(number == 100);
154 </PRE>
155 </P>
156 <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
157 <P>
158 By default, pattern and text are plain text, one byte per character. The UTF8
159 flag, passed to the constructor, causes both pattern and string to be treated
160 as UTF-8 text, still a byte stream but potentially multiple bytes per
161 character. In practice, the text is likelier to be UTF-8 than the pattern, but
162 the match returned may depend on the UTF8 flag, so always use it when matching
163 UTF8 text. For example, "." will match one byte normally but with UTF8 set may
164 match up to three bytes of a multi-byte character.
165 <pre>
166 Example:
167 pcrecpp::RE_Options options;
168 options.set_utf8();
169 pcrecpp::RE re(utf8_pattern, options);
170 re.FullMatch(utf8_string);
172 Example: using the convenience function UTF8():
173 pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
174 re.FullMatch(utf8_string);
175 </pre>
176 NOTE: The UTF8 flag is ignored if pcre was not configured with the
177 <pre>
178 --enable-utf8 flag.
179 </PRE>
180 </P>
182 <P>
183 PCRE defines some modifiers to change the behavior of the regular expression
184 engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
185 pass such modifiers to a RE class. Currently, the following modifiers are
186 supported:
187 <pre>
188 modifier description Perl corresponding
190 PCRE_CASELESS case insensitive match /i
191 PCRE_MULTILINE multiple lines match /m
192 PCRE_DOTALL dot matches newlines /s
193 PCRE_DOLLAR_ENDONLY $ matches only at end N/A
194 PCRE_EXTRA strict escape parsing N/A
195 PCRE_EXTENDED ignore white spaces /x
196 PCRE_UTF8 handles UTF8 chars built-in
197 PCRE_UNGREEDY reverses * and *? N/A
198 PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
199 </pre>
200 (*) Both Perl and PCRE allow non capturing parentheses by means of the
201 "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
202 capture, while (ab|cd) does.
203 </P>
204 <P>
205 For a full account on how each modifier works, please check the
206 PCRE API reference page.
207 </P>
208 <P>
209 For each modifier, there are two member functions whose name is made
210 out of the modifier in lowercase, without the "PCRE_" prefix. For
211 instance, PCRE_CASELESS is handled by
212 <pre>
213 bool caseless()
214 </pre>
215 which returns true if the modifier is set, and
216 <pre>
217 RE_Options & set_caseless(bool)
218 </pre>
219 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
220 accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
221 functions. Setting <i>match_limit</i> to a non-zero value will limit the
222 execution of pcre to keep it from doing bad things like blowing the stack or
223 taking an eternity to return a result. A value of 5000 is good enough to stop
224 stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
225 match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
226 which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
227 recurses. <b>match_limit()</b> limits the number of matches PCRE does;
228 <b>match_limit_recursion()</b> limits the depth of internal recursion, and
229 therefore the amount of stack that is used.
230 </P>
231 <P>
232 Normally, to pass one or more modifiers to a RE class, you declare
233 a <i>RE_Options</i> object, set the appropriate options, and pass this
234 object to a RE constructor. Example:
235 <pre>
236 RE_Options opt;
237 opt.set_caseless(true);
238 if (RE("HELLO", opt).PartialMatch("hello world")) ...
239 </pre>
240 RE_options has two constructors. The default constructor takes no arguments and
241 creates a set of flags that are off by default. The optional parameter
242 <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
243 This lets you do
244 <pre>
245 RE(pattern,
246 RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
247 </pre>
248 However, new code is better off doing
249 <pre>
250 RE(pattern,
251 RE_Options().set_caseless(true).set_multiline(true))
252 .PartialMatch(str);
253 </pre>
254 If you are going to pass one of the most used modifiers, there are some
255 convenience functions that return a RE_Options class with the
256 appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
257 <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
258 </P>
259 <P>
260 If you need to set several options at once, and you don't want to go through
261 the pains of declaring a RE_Options object and setting several options, there
262 is a parallel method that give you such ability on the fly. You can concatenate
263 several <b>set_xxxxx()</b> member functions, since each of them returns a
264 reference to its class object. For example, to pass PCRE_CASELESS,
265 PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
266 <pre>
267 RE(" ^ xyz \\s+ .* blah$",
268 RE_Options()
269 .set_caseless(true)
270 .set_extended(true)
271 .set_multiline(true)).PartialMatch(sometext);
273 </PRE>
274 </P>
275 <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
276 <P>
277 The "Consume" operation may be useful if you want to repeatedly
278 match regular expressions at the front of a string and skip over
279 them as they match. This requires use of the "StringPiece" type,
280 which represents a sub-range of a real string. Like RE, StringPiece
281 is defined in the pcrecpp namespace.
282 <pre>
283 Example: read lines of the form "var = value" from a string.
284 string contents = ...; // Fill string somehow
285 pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
287 string var;
288 int value;
289 pcrecpp::RE re("(\\w+) = (\\d+)\n");
290 while (re.Consume(&input, &var, &value)) {
291 ...;
292 }
293 </pre>
294 Each successful call to "Consume" will set "var/value", and also
295 advance "input" so it points past the matched text.
296 </P>
297 <P>
298 The "FindAndConsume" operation is similar to "Consume" but does not
299 anchor your match at the beginning of the string. For example, you
300 could extract all words from a string by repeatedly calling
301 <pre>
302 pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
303 </PRE>
304 </P>
305 <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
306 <P>
307 By default, if you pass a pointer to a numeric value, the
308 corresponding text is interpreted as a base-10 number. You can
309 instead wrap the pointer with a call to one of the operators Hex(),
310 Octal(), or CRadix() to interpret the text in another base. The
311 CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
312 prefixes, but defaults to base-10.
313 <pre>
314 Example:
315 int a, b, c, d;
316 pcrecpp::RE re("(.*) (.*) (.*) (.*)");
317 re.FullMatch("100 40 0100 0x40",
318 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
319 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
320 </pre>
321 will leave 64 in a, b, c, and d.
322 </P>
323 <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
324 <P>
325 You can replace the first match of "pattern" in "str" with "rewrite".
326 Within "rewrite", backslash-escaped digits (\1 to \9) can be
327 used to insert text matching corresponding parenthesized group
328 from the pattern. \0 in "rewrite" refers to the entire matching
329 text. For example:
330 <pre>
331 string s = "yabba dabba doo";
332 pcrecpp::RE("b+").Replace("d", &s);
333 </pre>
334 will leave "s" containing "yada dabba doo". The result is true if the pattern
335 matches and a replacement occurs, false otherwise.
336 </P>
337 <P>
338 <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
339 occurrences of the pattern in the string with the rewrite. Replacements are
340 not subject to re-matching. For example:
341 <pre>
342 string s = "yabba dabba doo";
343 pcrecpp::RE("b+").GlobalReplace("d", &s);
344 </pre>
345 will leave "s" containing "yada dada doo". It returns the number of
346 replacements made.
347 </P>
348 <P>
349 <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
350 "rewrite" is copied into "out" (an additional argument) with substitutions.
351 The non-matching portions of "text" are ignored. Returns true iff a match
352 occurred and the extraction happened successfully; if no match occurs, the
353 string is left unaffected.
354 </P>
355 <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
356 <P>
357 The C++ wrapper was contributed by Google Inc.
358 <br>
359 Copyright &copy; 2007 Google Inc.
360 <br>
361 </P>
362 <br><a name="SEC12" href="#TOC1">REVISION</a><br>
363 <P>
364 Last updated: 08 January 2012
365 <br>
366 <p>
367 Return to the <a href="index.html">PCRE index page</a>.
368 </p>


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