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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.
39 </P>
40 <br><a name="SEC3" href="#TOC1">MATCHING INTERFACE</a><br>
41 <P>
42 The "FullMatch" operation checks that supplied text matches a supplied pattern
43 exactly. If pointer arguments are supplied, it copies matched sub-strings that
44 match sub-patterns into them.
45 <pre>
46 Example: successful match
47 pcrecpp::RE re("h.*o");
48 re.FullMatch("hello");
50 Example: unsuccessful match (requires full match):
51 pcrecpp::RE re("e");
52 !re.FullMatch("hello");
54 Example: creating a temporary RE object:
55 pcrecpp::RE("h.*o").FullMatch("hello");
56 </pre>
57 You can pass in a "const char*" or a "string" for "text". The examples below
58 tend to use a const char*. You can, as in the different examples above, store
59 the RE object explicitly in a variable or use a temporary RE object. The
60 examples below use one mode or the other arbitrarily. Either could correctly be
61 used for any of these examples.
62 </P>
63 <P>
64 You must supply extra pointer arguments to extract matched subpieces.
65 <pre>
66 Example: extracts "ruby" into "s" and 1234 into "i"
67 int i;
68 string s;
69 pcrecpp::RE re("(\\w+):(\\d+)");
70 re.FullMatch("ruby:1234", &s, &i);
72 Example: does not try to extract any extra sub-patterns
73 re.FullMatch("ruby:1234", &s);
75 Example: does not try to extract into NULL
76 re.FullMatch("ruby:1234", NULL, &i);
78 Example: integer overflow causes failure
79 !re.FullMatch("ruby:1234567891234", NULL, &i);
81 Example: fails because there aren't enough sub-patterns:
82 !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
84 Example: fails because string cannot be stored in integer
85 !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
86 </pre>
87 The provided pointer arguments can be pointers to any scalar numeric
88 type, or one of:
89 <pre>
90 string (matched piece is copied to string)
91 StringPiece (StringPiece is mutated to point to matched piece)
92 T (where "bool T::ParseFrom(const char*, int)" exists)
93 NULL (the corresponding matched sub-pattern is not copied)
94 </pre>
95 The function returns true iff all of the following conditions are satisfied:
96 <pre>
97 a. "text" matches "pattern" exactly;
99 b. The number of matched sub-patterns is &#62;= number of supplied
100 pointers;
102 c. The "i"th argument has a suitable type for holding the
103 string captured as the "i"th sub-pattern. If you pass in
104 NULL for the "i"th argument, or pass fewer arguments than
105 number of sub-patterns, "i"th captured sub-pattern is
106 ignored.
107 </pre>
108 CAVEAT: An optional sub-pattern that does not exist in the matched
109 string is assigned the empty string. Therefore, the following will
110 return false (because the empty string is not a valid number):
111 <pre>
112 int number;
113 pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
114 </pre>
115 The matching interface supports at most 16 arguments per call.
116 If you need more, consider using the more general interface
117 <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
118 <b>DoMatch</b>.
119 </P>
120 <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
121 <P>
122 You can use the "QuoteMeta" operation to insert backslashes before all
123 potentially meaningful characters in a string. The returned string, used as a
124 regular expression, will exactly match the original string.
125 <pre>
126 Example:
127 string quoted = RE::QuoteMeta(unquoted);
128 </pre>
129 Note that it's legal to escape a character even if it has no special meaning in
130 a regular expression -- so this function does that. (This also makes it
131 identical to the perl function of the same name; see "perldoc -f quotemeta".)
132 For example, "1.5-2.0?" becomes "1\.5\-2\.0\?".
133 </P>
134 <br><a name="SEC5" href="#TOC1">PARTIAL MATCHES</a><br>
135 <P>
136 You can use the "PartialMatch" operation when you want the pattern
137 to match any substring of the text.
138 <pre>
139 Example: simple search for a string:
140 pcrecpp::RE("ell").PartialMatch("hello");
142 Example: find first number in a string:
143 int number;
144 pcrecpp::RE re("(\\d+)");
145 re.PartialMatch("x*100 + 20", &number);
146 assert(number == 100);
147 </PRE>
148 </P>
149 <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
150 <P>
151 By default, pattern and text are plain text, one byte per character. The UTF8
152 flag, passed to the constructor, causes both pattern and string to be treated
153 as UTF-8 text, still a byte stream but potentially multiple bytes per
154 character. In practice, the text is likelier to be UTF-8 than the pattern, but
155 the match returned may depend on the UTF8 flag, so always use it when matching
156 UTF8 text. For example, "." will match one byte normally but with UTF8 set may
157 match up to three bytes of a multi-byte character.
158 <pre>
159 Example:
160 pcrecpp::RE_Options options;
161 options.set_utf8();
162 pcrecpp::RE re(utf8_pattern, options);
163 re.FullMatch(utf8_string);
165 Example: using the convenience function UTF8():
166 pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
167 re.FullMatch(utf8_string);
168 </pre>
169 NOTE: The UTF8 flag is ignored if pcre was not configured with the
170 <pre>
171 --enable-utf8 flag.
172 </PRE>
173 </P>
175 <P>
176 PCRE defines some modifiers to change the behavior of the regular expression
177 engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
178 pass such modifiers to a RE class. Currently, the following modifiers are
179 supported:
180 <pre>
181 modifier description Perl corresponding
183 PCRE_CASELESS case insensitive match /i
184 PCRE_MULTILINE multiple lines match /m
185 PCRE_DOTALL dot matches newlines /s
186 PCRE_DOLLAR_ENDONLY $ matches only at end N/A
187 PCRE_EXTRA strict escape parsing N/A
188 PCRE_EXTENDED ignore whitespaces /x
189 PCRE_UTF8 handles UTF8 chars built-in
190 PCRE_UNGREEDY reverses * and *? N/A
191 PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
192 </pre>
193 (*) Both Perl and PCRE allow non capturing parentheses by means of the
194 "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
195 capture, while (ab|cd) does.
196 </P>
197 <P>
198 For a full account on how each modifier works, please check the
199 PCRE API reference page.
200 </P>
201 <P>
202 For each modifier, there are two member functions whose name is made
203 out of the modifier in lowercase, without the "PCRE_" prefix. For
204 instance, PCRE_CASELESS is handled by
205 <pre>
206 bool caseless()
207 </pre>
208 which returns true if the modifier is set, and
209 <pre>
210 RE_Options & set_caseless(bool)
211 </pre>
212 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
213 accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
214 functions. Setting <i>match_limit</i> to a non-zero value will limit the
215 execution of pcre to keep it from doing bad things like blowing the stack or
216 taking an eternity to return a result. A value of 5000 is good enough to stop
217 stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
218 match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
219 which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
220 recurses. <b>match_limit()</b> limits the number of matches PCRE does;
221 <b>match_limit_recursion()</b> limits the depth of internal recursion, and
222 therefore the amount of stack that is used.
223 </P>
224 <P>
225 Normally, to pass one or more modifiers to a RE class, you declare
226 a <i>RE_Options</i> object, set the appropriate options, and pass this
227 object to a RE constructor. Example:
228 <pre>
229 RE_options opt;
230 opt.set_caseless(true);
231 if (RE("HELLO", opt).PartialMatch("hello world")) ...
232 </pre>
233 RE_options has two constructors. The default constructor takes no arguments and
234 creates a set of flags that are off by default. The optional parameter
235 <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
236 This lets you do
237 <pre>
238 RE(pattern,
239 RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
240 </pre>
241 However, new code is better off doing
242 <pre>
243 RE(pattern,
244 RE_Options().set_caseless(true).set_multiline(true))
245 .PartialMatch(str);
246 </pre>
247 If you are going to pass one of the most used modifiers, there are some
248 convenience functions that return a RE_Options class with the
249 appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
250 <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
251 </P>
252 <P>
253 If you need to set several options at once, and you don't want to go through
254 the pains of declaring a RE_Options object and setting several options, there
255 is a parallel method that give you such ability on the fly. You can concatenate
256 several <b>set_xxxxx()</b> member functions, since each of them returns a
257 reference to its class object. For example, to pass PCRE_CASELESS,
258 PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
259 <pre>
260 RE(" ^ xyz \\s+ .* blah$",
261 RE_Options()
262 .set_caseless(true)
263 .set_extended(true)
264 .set_multiline(true)).PartialMatch(sometext);
266 </PRE>
267 </P>
268 <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
269 <P>
270 The "Consume" operation may be useful if you want to repeatedly
271 match regular expressions at the front of a string and skip over
272 them as they match. This requires use of the "StringPiece" type,
273 which represents a sub-range of a real string. Like RE, StringPiece
274 is defined in the pcrecpp namespace.
275 <pre>
276 Example: read lines of the form "var = value" from a string.
277 string contents = ...; // Fill string somehow
278 pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
279 </PRE>
280 </P>
281 <P>
282 <pre>
283 string var;
284 int value;
285 pcrecpp::RE re("(\\w+) = (\\d+)\n");
286 while (re.Consume(&input, &var, &value)) {
287 ...;
288 }
289 </pre>
290 Each successful call to "Consume" will set "var/value", and also
291 advance "input" so it points past the matched text.
292 </P>
293 <P>
294 The "FindAndConsume" operation is similar to "Consume" but does not
295 anchor your match at the beginning of the string. For example, you
296 could extract all words from a string by repeatedly calling
297 <pre>
298 pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
299 </PRE>
300 </P>
301 <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
302 <P>
303 By default, if you pass a pointer to a numeric value, the
304 corresponding text is interpreted as a base-10 number. You can
305 instead wrap the pointer with a call to one of the operators Hex(),
306 Octal(), or CRadix() to interpret the text in another base. The
307 CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
308 prefixes, but defaults to base-10.
309 <pre>
310 Example:
311 int a, b, c, d;
312 pcrecpp::RE re("(.*) (.*) (.*) (.*)");
313 re.FullMatch("100 40 0100 0x40",
314 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
315 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
316 </pre>
317 will leave 64 in a, b, c, and d.
318 </P>
319 <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
320 <P>
321 You can replace the first match of "pattern" in "str" with "rewrite".
322 Within "rewrite", backslash-escaped digits (\1 to \9) can be
323 used to insert text matching corresponding parenthesized group
324 from the pattern. \0 in "rewrite" refers to the entire matching
325 text. For example:
326 <pre>
327 string s = "yabba dabba doo";
328 pcrecpp::RE("b+").Replace("d", &s);
329 </pre>
330 will leave "s" containing "yada dabba doo". The result is true if the pattern
331 matches and a replacement occurs, false otherwise.
332 </P>
333 <P>
334 <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
335 occurrences of the pattern in the string with the rewrite. Replacements are
336 not subject to re-matching. For example:
337 <pre>
338 string s = "yabba dabba doo";
339 pcrecpp::RE("b+").GlobalReplace("d", &s);
340 </pre>
341 will leave "s" containing "yada dada doo". It returns the number of
342 replacements made.
343 </P>
344 <P>
345 <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
346 "rewrite" is copied into "out" (an additional argument) with substitutions.
347 The non-matching portions of "text" are ignored. Returns true iff a match
348 occurred and the extraction happened successfully; if no match occurs, the
349 string is left unaffected.
350 </P>
351 <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
352 <P>
353 The C++ wrapper was contributed by Google Inc.
354 <br>
355 Copyright &copy; 2006 Google Inc.
356 <br>
357 </P>
358 <br><a name="SEC12" href="#TOC1">REVISION</a><br>
359 <P>
360 Last updated: 06 March 2007
361 <br>
362 <p>
363 Return to the <a href="index.html">PCRE index page</a>.
364 </p>


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