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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">PARTIAL MATCHES</a>
20 <li><a name="TOC5" href="#SEC5">UTF-8 AND THE MATCHING INTERFACE</a>
22 <li><a name="TOC7" href="#SEC7">SCANNING TEXT INCREMENTALLY</a>
23 <li><a name="TOC8" href="#SEC8">PARSING HEX/OCTAL/C-RADIX NUMBERS</a>
24 <li><a name="TOC9" href="#SEC9">REPLACING PARTS OF STRINGS</a>
25 <li><a name="TOC10" href="#SEC10">AUTHOR</a>
26 </ul>
27 <br><a name="SEC1" href="#TOC1">SYNOPSIS OF C++ WRAPPER</a><br>
28 <P>
29 <b>#include &#60;pcrecpp.h&#62;</b>
30 </P>
31 <P>
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 The matching interface supports at most 16 arguments per call.
109 If you need more, consider using the more general interface
110 <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
111 <b>DoMatch</b>.
112 </P>
113 <br><a name="SEC4" href="#TOC1">PARTIAL MATCHES</a><br>
114 <P>
115 You can use the "PartialMatch" operation when you want the pattern
116 to match any substring of the text.
117 <pre>
118 Example: simple search for a string:
119 pcrecpp::RE("ell").PartialMatch("hello");
121 Example: find first number in a string:
122 int number;
123 pcrecpp::RE re("(\\d+)");
124 re.PartialMatch("x*100 + 20", &number);
125 assert(number == 100);
126 </PRE>
127 </P>
128 <br><a name="SEC5" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
129 <P>
130 By default, pattern and text are plain text, one byte per character. The UTF8
131 flag, passed to the constructor, causes both pattern and string to be treated
132 as UTF-8 text, still a byte stream but potentially multiple bytes per
133 character. In practice, the text is likelier to be UTF-8 than the pattern, but
134 the match returned may depend on the UTF8 flag, so always use it when matching
135 UTF8 text. For example, "." will match one byte normally but with UTF8 set may
136 match up to three bytes of a multi-byte character.
137 <pre>
138 Example:
139 pcrecpp::RE_Options options;
140 options.set_utf8();
141 pcrecpp::RE re(utf8_pattern, options);
142 re.FullMatch(utf8_string);
144 Example: using the convenience function UTF8():
145 pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
146 re.FullMatch(utf8_string);
147 </pre>
148 NOTE: The UTF8 flag is ignored if pcre was not configured with the
149 <pre>
150 --enable-utf8 flag.
151 </PRE>
152 </P>
154 <P>
155 PCRE defines some modifiers to change the behavior of the regular expression
156 engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
157 pass such modifiers to a RE class. Currently, the following modifiers are
158 supported:
159 <pre>
160 modifier description Perl corresponding
162 PCRE_CASELESS case insensitive match /i
163 PCRE_MULTILINE multiple lines match /m
164 PCRE_DOTALL dot matches newlines /s
165 PCRE_DOLLAR_ENDONLY $ matches only at end N/A
166 PCRE_EXTRA strict escape parsing N/A
167 PCRE_EXTENDED ignore whitespaces /x
168 PCRE_UTF8 handles UTF8 chars built-in
169 PCRE_UNGREEDY reverses * and *? N/A
170 PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
171 </pre>
172 (*) Both Perl and PCRE allow non capturing parentheses by means of the
173 "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
174 capture, while (ab|cd) does.
175 </P>
176 <P>
177 For a full account on how each modifier works, please check the
178 PCRE API reference page.
179 </P>
180 <P>
181 For each modifier, there are two member functions whose name is made
182 out of the modifier in lowercase, without the "PCRE_" prefix. For
183 instance, PCRE_CASELESS is handled by
184 <pre>
185 bool caseless()
186 </pre>
187 which returns true if the modifier is set, and
188 <pre>
189 RE_Options & set_caseless(bool)
190 </pre>
191 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
192 accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
193 functions. Setting <i>match_limit</i> to a non-zero value will limit the
194 execution of pcre to keep it from doing bad things like blowing the stack or
195 taking an eternity to return a result. A value of 5000 is good enough to stop
196 stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
197 match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
198 which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
199 recurses. <b>match_limit()</b> limits the number of matches PCRE does;
200 <b>match_limit_recursion()</b> limits the depth of internal recursion, and
201 therefore the amount of stack that is used.
202 </P>
203 <P>
204 Normally, to pass one or more modifiers to a RE class, you declare
205 a <i>RE_Options</i> object, set the appropriate options, and pass this
206 object to a RE constructor. Example:
207 <pre>
208 RE_options opt;
209 opt.set_caseless(true);
210 if (RE("HELLO", opt).PartialMatch("hello world")) ...
211 </pre>
212 RE_options has two constructors. The default constructor takes no arguments and
213 creates a set of flags that are off by default. The optional parameter
214 <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
215 This lets you do
216 <pre>
217 RE(pattern,
218 RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
219 </pre>
220 However, new code is better off doing
221 <pre>
222 RE(pattern,
223 RE_Options().set_caseless(true).set_multiline(true))
224 .PartialMatch(str);
225 </pre>
226 If you are going to pass one of the most used modifiers, there are some
227 convenience functions that return a RE_Options class with the
228 appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
229 <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
230 </P>
231 <P>
232 If you need to set several options at once, and you don't want to go through
233 the pains of declaring a RE_Options object and setting several options, there
234 is a parallel method that give you such ability on the fly. You can concatenate
235 several <b>set_xxxxx()</b> member functions, since each of them returns a
236 reference to its class object. For example, to pass PCRE_CASELESS,
237 PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
238 <pre>
239 RE(" ^ xyz \\s+ .* blah$",
240 RE_Options()
241 .set_caseless(true)
242 .set_extended(true)
243 .set_multiline(true)).PartialMatch(sometext);
245 </PRE>
246 </P>
247 <br><a name="SEC7" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
248 <P>
249 The "Consume" operation may be useful if you want to repeatedly
250 match regular expressions at the front of a string and skip over
251 them as they match. This requires use of the "StringPiece" type,
252 which represents a sub-range of a real string. Like RE, StringPiece
253 is defined in the pcrecpp namespace.
254 <pre>
255 Example: read lines of the form "var = value" from a string.
256 string contents = ...; // Fill string somehow
257 pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
258 </PRE>
259 </P>
260 <P>
261 <pre>
262 string var;
263 int value;
264 pcrecpp::RE re("(\\w+) = (\\d+)\n");
265 while (re.Consume(&input, &var, &value)) {
266 ...;
267 }
268 </pre>
269 Each successful call to "Consume" will set "var/value", and also
270 advance "input" so it points past the matched text.
271 </P>
272 <P>
273 The "FindAndConsume" operation is similar to "Consume" but does not
274 anchor your match at the beginning of the string. For example, you
275 could extract all words from a string by repeatedly calling
276 <pre>
277 pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
278 </PRE>
279 </P>
280 <br><a name="SEC8" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
281 <P>
282 By default, if you pass a pointer to a numeric value, the
283 corresponding text is interpreted as a base-10 number. You can
284 instead wrap the pointer with a call to one of the operators Hex(),
285 Octal(), or CRadix() to interpret the text in another base. The
286 CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
287 prefixes, but defaults to base-10.
288 <pre>
289 Example:
290 int a, b, c, d;
291 pcrecpp::RE re("(.*) (.*) (.*) (.*)");
292 re.FullMatch("100 40 0100 0x40",
293 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
294 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
295 </pre>
296 will leave 64 in a, b, c, and d.
297 </P>
298 <br><a name="SEC9" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
299 <P>
300 You can replace the first match of "pattern" in "str" with "rewrite".
301 Within "rewrite", backslash-escaped digits (\1 to \9) can be
302 used to insert text matching corresponding parenthesized group
303 from the pattern. \0 in "rewrite" refers to the entire matching
304 text. For example:
305 <pre>
306 string s = "yabba dabba doo";
307 pcrecpp::RE("b+").Replace("d", &s);
308 </pre>
309 will leave "s" containing "yada dabba doo". The result is true if the pattern
310 matches and a replacement occurs, false otherwise.
311 </P>
312 <P>
313 <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
314 occurrences of the pattern in the string with the rewrite. Replacements are
315 not subject to re-matching. For example:
316 <pre>
317 string s = "yabba dabba doo";
318 pcrecpp::RE("b+").GlobalReplace("d", &s);
319 </pre>
320 will leave "s" containing "yada dada doo". It returns the number of
321 replacements made.
322 </P>
323 <P>
324 <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
325 "rewrite" is copied into "out" (an additional argument) with substitutions.
326 The non-matching portions of "text" are ignored. Returns true iff a match
327 occurred and the extraction happened successfully; if no match occurs, the
328 string is left unaffected.
329 </P>
330 <br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
331 <P>
332 The C++ wrapper was contributed by Google Inc.
333 <br>
334 Copyright &copy; 2005 Google Inc.
335 <p>
336 Return to the <a href="index.html">PCRE index page</a>.
337 </p>

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