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1 nigel 77 <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 ph10 111 <p>
11 nigel 77 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 ph10 111 <br>
15 nigel 77 <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 nigel 93 <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 ph10 99 <li><a name="TOC12" href="#SEC12">REVISION</a>
28 nigel 77 </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 nigel 81 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 ph10 903 further details. Note that the C++ wrapper supports only the original 8-bit
39 ph10 869 PCRE library. There is no 16-bit support at present.
40 nigel 77 </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 ph10 286 void * NULL for the "i"th argument, or a non-void * NULL
106     of the correct type, or pass fewer arguments than the
107 nigel 77 number of sub-patterns, "i"th captured sub-pattern is
108     ignored.
109     </pre>
110 nigel 93 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 nigel 77 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 ph10 392 <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 nigel 93 <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
128 nigel 77 <P>
129 nigel 93 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 nigel 77 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 nigel 93 <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
157 nigel 77 <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>
181 nigel 93 <br><a name="SEC7" href="#TOC1">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a><br>
182 nigel 77 <P>
183 nigel 81 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 whitespaces /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 nigel 87 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
220 nigel 81 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 nigel 87 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 nigel 81 </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 ph10 654 RE_Options opt;
237 nigel 81 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 nigel 93 <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
276 nigel 81 <P>
277 nigel 77 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
286 ph10 583
287 nigel 77 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 nigel 93 <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
306 nigel 77 <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 nigel 93 <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
324 nigel 77 <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 nigel 93 <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
356 nigel 77 <P>
357     The C++ wrapper was contributed by Google Inc.
358     <br>
359 ph10 123 Copyright &copy; 2007 Google Inc.
360 ph10 99 <br>
361     </P>
362     <br><a name="SEC12" href="#TOC1">REVISION</a><br>
363     <P>
364 ph10 869 Last updated: 08 January 2012
365 ph10 99 <br>
366 nigel 77 <p>
367     Return to the <a href="index.html">PCRE index page</a>.
368     </p>


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