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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_CONFIG_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.
198 </P>
199 <P>
200 Normally, to pass one or more modifiers to a RE class, you declare
201 a <i>RE_Options</i> object, set the appropriate options, and pass this
202 object to a RE constructor. Example:
203 <pre>
204 RE_options opt;
205 opt.set_caseless(true);
206 if (RE("HELLO", opt).PartialMatch("hello world")) ...
207 </pre>
208 RE_options has two constructors. The default constructor takes no arguments and
209 creates a set of flags that are off by default. The optional parameter
210 <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
211 This lets you do
212 <pre>
213 RE(pattern,
214 RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
215 </pre>
216 However, new code is better off doing
217 <pre>
218 RE(pattern,
219 RE_Options().set_caseless(true).set_multiline(true))
220 .PartialMatch(str);
221 </pre>
222 If you are going to pass one of the most used modifiers, there are some
223 convenience functions that return a RE_Options class with the
224 appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
225 <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
226 </P>
227 <P>
228 If you need to set several options at once, and you don't want to go through
229 the pains of declaring a RE_Options object and setting several options, there
230 is a parallel method that give you such ability on the fly. You can concatenate
231 several <b>set_xxxxx()</b> member functions, since each of them returns a
232 reference to its class object. For example, to pass PCRE_CASELESS,
233 PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
234 <pre>
235 RE(" ^ xyz \\s+ .* blah$",
236 RE_Options()
237 .set_caseless(true)
238 .set_extended(true)
239 .set_multiline(true)).PartialMatch(sometext);
241 </PRE>
242 </P>
243 <br><a name="SEC7" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
244 <P>
245 The "Consume" operation may be useful if you want to repeatedly
246 match regular expressions at the front of a string and skip over
247 them as they match. This requires use of the "StringPiece" type,
248 which represents a sub-range of a real string. Like RE, StringPiece
249 is defined in the pcrecpp namespace.
250 <pre>
251 Example: read lines of the form "var = value" from a string.
252 string contents = ...; // Fill string somehow
253 pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
254 </PRE>
255 </P>
256 <P>
257 <pre>
258 string var;
259 int value;
260 pcrecpp::RE re("(\\w+) = (\\d+)\n");
261 while (re.Consume(&input, &var, &value)) {
262 ...;
263 }
264 </pre>
265 Each successful call to "Consume" will set "var/value", and also
266 advance "input" so it points past the matched text.
267 </P>
268 <P>
269 The "FindAndConsume" operation is similar to "Consume" but does not
270 anchor your match at the beginning of the string. For example, you
271 could extract all words from a string by repeatedly calling
272 <pre>
273 pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
274 </PRE>
275 </P>
276 <br><a name="SEC8" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
277 <P>
278 By default, if you pass a pointer to a numeric value, the
279 corresponding text is interpreted as a base-10 number. You can
280 instead wrap the pointer with a call to one of the operators Hex(),
281 Octal(), or CRadix() to interpret the text in another base. The
282 CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
283 prefixes, but defaults to base-10.
284 <pre>
285 Example:
286 int a, b, c, d;
287 pcrecpp::RE re("(.*) (.*) (.*) (.*)");
288 re.FullMatch("100 40 0100 0x40",
289 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
290 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
291 </pre>
292 will leave 64 in a, b, c, and d.
293 </P>
294 <br><a name="SEC9" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
295 <P>
296 You can replace the first match of "pattern" in "str" with "rewrite".
297 Within "rewrite", backslash-escaped digits (\1 to \9) can be
298 used to insert text matching corresponding parenthesized group
299 from the pattern. \0 in "rewrite" refers to the entire matching
300 text. For example:
301 <pre>
302 string s = "yabba dabba doo";
303 pcrecpp::RE("b+").Replace("d", &s);
304 </pre>
305 will leave "s" containing "yada dabba doo". The result is true if the pattern
306 matches and a replacement occurs, false otherwise.
307 </P>
308 <P>
309 <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
310 occurrences of the pattern in the string with the rewrite. Replacements are
311 not subject to re-matching. For example:
312 <pre>
313 string s = "yabba dabba doo";
314 pcrecpp::RE("b+").GlobalReplace("d", &s);
315 </pre>
316 will leave "s" containing "yada dada doo". It returns the number of
317 replacements made.
318 </P>
319 <P>
320 <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
321 "rewrite" is copied into "out" (an additional argument) with substitutions.
322 The non-matching portions of "text" are ignored. Returns true iff a match
323 occurred and the extraction happened successfully; if no match occurs, the
324 string is left unaffected.
325 </P>
326 <br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
327 <P>
328 The C++ wrapper was contributed by Google Inc.
329 <br>
330 Copyright &copy; 2005 Google Inc.
331 <p>
332 Return to the <a href="index.html">PCRE index page</a>.
333 </p>

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