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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>
22: <li><a name="TOC7" href="#SEC7">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</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 <pcrecpp.h></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");
49:
50: Example: unsuccessful match (requires full match):
51: pcrecpp::RE re("e");
52: !re.FullMatch("hello");
53:
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);
71:
72: Example: does not try to extract any extra sub-patterns
73: re.FullMatch("ruby:1234", &s);
74:
75: Example: does not try to extract into NULL
76: re.FullMatch("ruby:1234", NULL, &i);
77:
78: Example: integer overflow causes failure
79: !re.FullMatch("ruby:1234567891234", NULL, &i);
80:
81: Example: fails because there aren't enough sub-patterns:
82: !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
83:
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;
98:
99: b. The number of matched sub-patterns is >= number of supplied
100: pointers;
101:
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: void * NULL for the "i"th argument, or a non-void * NULL
105: of the correct type, or pass fewer arguments than the
106: number of sub-patterns, "i"th captured sub-pattern is
107: ignored.
108: </pre>
109: CAVEAT: An optional sub-pattern that does not exist in the matched
110: string is assigned the empty string. Therefore, the following will
111: return false (because the empty string is not a valid number):
112: <pre>
113: int number;
114: pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
115: </pre>
116: The matching interface supports at most 16 arguments per call.
117: If you need more, consider using the more general interface
118: <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
119: <b>DoMatch</b>.
120: </P>
121: <P>
122: NOTE: Do not use <b>no_arg</b>, which is used internally to mark the end of a
123: list of optional arguments, as a placeholder for missing arguments, as this can
124: lead to segfaults.
125: </P>
126: <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
127: <P>
128: You can use the "QuoteMeta" operation to insert backslashes before all
129: potentially meaningful characters in a string. The returned string, used as a
130: regular expression, will exactly match the original string.
131: <pre>
132: Example:
133: string quoted = RE::QuoteMeta(unquoted);
134: </pre>
135: Note that it's legal to escape a character even if it has no special meaning in
136: a regular expression -- so this function does that. (This also makes it
137: identical to the perl function of the same name; see "perldoc -f quotemeta".)
138: For example, "1.5-2.0?" becomes "1\.5\-2\.0\?".
139: </P>
140: <br><a name="SEC5" href="#TOC1">PARTIAL MATCHES</a><br>
141: <P>
142: You can use the "PartialMatch" operation when you want the pattern
143: to match any substring of the text.
144: <pre>
145: Example: simple search for a string:
146: pcrecpp::RE("ell").PartialMatch("hello");
147:
148: Example: find first number in a string:
149: int number;
150: pcrecpp::RE re("(\\d+)");
151: re.PartialMatch("x*100 + 20", &number);
152: assert(number == 100);
153: </PRE>
154: </P>
155: <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
156: <P>
157: By default, pattern and text are plain text, one byte per character. The UTF8
158: flag, passed to the constructor, causes both pattern and string to be treated
159: as UTF-8 text, still a byte stream but potentially multiple bytes per
160: character. In practice, the text is likelier to be UTF-8 than the pattern, but
161: the match returned may depend on the UTF8 flag, so always use it when matching
162: UTF8 text. For example, "." will match one byte normally but with UTF8 set may
163: match up to three bytes of a multi-byte character.
164: <pre>
165: Example:
166: pcrecpp::RE_Options options;
167: options.set_utf8();
168: pcrecpp::RE re(utf8_pattern, options);
169: re.FullMatch(utf8_string);
170:
171: Example: using the convenience function UTF8():
172: pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
173: re.FullMatch(utf8_string);
174: </pre>
175: NOTE: The UTF8 flag is ignored if pcre was not configured with the
176: <pre>
177: --enable-utf8 flag.
178: </PRE>
179: </P>
180: <br><a name="SEC7" href="#TOC1">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a><br>
181: <P>
182: PCRE defines some modifiers to change the behavior of the regular expression
183: engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
184: pass such modifiers to a RE class. Currently, the following modifiers are
185: supported:
186: <pre>
187: modifier description Perl corresponding
188:
189: PCRE_CASELESS case insensitive match /i
190: PCRE_MULTILINE multiple lines match /m
191: PCRE_DOTALL dot matches newlines /s
192: PCRE_DOLLAR_ENDONLY $ matches only at end N/A
193: PCRE_EXTRA strict escape parsing N/A
194: PCRE_EXTENDED ignore whitespaces /x
195: PCRE_UTF8 handles UTF8 chars built-in
196: PCRE_UNGREEDY reverses * and *? N/A
197: PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
198: </pre>
199: (*) Both Perl and PCRE allow non capturing parentheses by means of the
200: "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
201: capture, while (ab|cd) does.
202: </P>
203: <P>
204: For a full account on how each modifier works, please check the
205: PCRE API reference page.
206: </P>
207: <P>
208: For each modifier, there are two member functions whose name is made
209: out of the modifier in lowercase, without the "PCRE_" prefix. For
210: instance, PCRE_CASELESS is handled by
211: <pre>
212: bool caseless()
213: </pre>
214: which returns true if the modifier is set, and
215: <pre>
216: RE_Options & set_caseless(bool)
217: </pre>
218: which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
219: accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
220: functions. Setting <i>match_limit</i> to a non-zero value will limit the
221: execution of pcre to keep it from doing bad things like blowing the stack or
222: taking an eternity to return a result. A value of 5000 is good enough to stop
223: stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
224: match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
225: which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
226: recurses. <b>match_limit()</b> limits the number of matches PCRE does;
227: <b>match_limit_recursion()</b> limits the depth of internal recursion, and
228: therefore the amount of stack that is used.
229: </P>
230: <P>
231: Normally, to pass one or more modifiers to a RE class, you declare
232: a <i>RE_Options</i> object, set the appropriate options, and pass this
233: object to a RE constructor. Example:
234: <pre>
235: RE_Options opt;
236: opt.set_caseless(true);
237: if (RE("HELLO", opt).PartialMatch("hello world")) ...
238: </pre>
239: RE_options has two constructors. The default constructor takes no arguments and
240: creates a set of flags that are off by default. The optional parameter
241: <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
242: This lets you do
243: <pre>
244: RE(pattern,
245: RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
246: </pre>
247: However, new code is better off doing
248: <pre>
249: RE(pattern,
250: RE_Options().set_caseless(true).set_multiline(true))
251: .PartialMatch(str);
252: </pre>
253: If you are going to pass one of the most used modifiers, there are some
254: convenience functions that return a RE_Options class with the
255: appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
256: <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
257: </P>
258: <P>
259: If you need to set several options at once, and you don't want to go through
260: the pains of declaring a RE_Options object and setting several options, there
261: is a parallel method that give you such ability on the fly. You can concatenate
262: several <b>set_xxxxx()</b> member functions, since each of them returns a
263: reference to its class object. For example, to pass PCRE_CASELESS,
264: PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
265: <pre>
266: RE(" ^ xyz \\s+ .* blah$",
267: RE_Options()
268: .set_caseless(true)
269: .set_extended(true)
270: .set_multiline(true)).PartialMatch(sometext);
271:
272: </PRE>
273: </P>
274: <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
275: <P>
276: The "Consume" operation may be useful if you want to repeatedly
277: match regular expressions at the front of a string and skip over
278: them as they match. This requires use of the "StringPiece" type,
279: which represents a sub-range of a real string. Like RE, StringPiece
280: is defined in the pcrecpp namespace.
281: <pre>
282: Example: read lines of the form "var = value" from a string.
283: string contents = ...; // Fill string somehow
284: pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
285:
286: string var;
287: int value;
288: pcrecpp::RE re("(\\w+) = (\\d+)\n");
289: while (re.Consume(&input, &var, &value)) {
290: ...;
291: }
292: </pre>
293: Each successful call to "Consume" will set "var/value", and also
294: advance "input" so it points past the matched text.
295: </P>
296: <P>
297: The "FindAndConsume" operation is similar to "Consume" but does not
298: anchor your match at the beginning of the string. For example, you
299: could extract all words from a string by repeatedly calling
300: <pre>
301: pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
302: </PRE>
303: </P>
304: <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
305: <P>
306: By default, if you pass a pointer to a numeric value, the
307: corresponding text is interpreted as a base-10 number. You can
308: instead wrap the pointer with a call to one of the operators Hex(),
309: Octal(), or CRadix() to interpret the text in another base. The
310: CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
311: prefixes, but defaults to base-10.
312: <pre>
313: Example:
314: int a, b, c, d;
315: pcrecpp::RE re("(.*) (.*) (.*) (.*)");
316: re.FullMatch("100 40 0100 0x40",
317: pcrecpp::Octal(&a), pcrecpp::Hex(&b),
318: pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
319: </pre>
320: will leave 64 in a, b, c, and d.
321: </P>
322: <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
323: <P>
324: You can replace the first match of "pattern" in "str" with "rewrite".
325: Within "rewrite", backslash-escaped digits (\1 to \9) can be
326: used to insert text matching corresponding parenthesized group
327: from the pattern. \0 in "rewrite" refers to the entire matching
328: text. For example:
329: <pre>
330: string s = "yabba dabba doo";
331: pcrecpp::RE("b+").Replace("d", &s);
332: </pre>
333: will leave "s" containing "yada dabba doo". The result is true if the pattern
334: matches and a replacement occurs, false otherwise.
335: </P>
336: <P>
337: <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
338: occurrences of the pattern in the string with the rewrite. Replacements are
339: not subject to re-matching. For example:
340: <pre>
341: string s = "yabba dabba doo";
342: pcrecpp::RE("b+").GlobalReplace("d", &s);
343: </pre>
344: will leave "s" containing "yada dada doo". It returns the number of
345: replacements made.
346: </P>
347: <P>
348: <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
349: "rewrite" is copied into "out" (an additional argument) with substitutions.
350: The non-matching portions of "text" are ignored. Returns true iff a match
351: occurred and the extraction happened successfully; if no match occurs, the
352: string is left unaffected.
353: </P>
354: <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
355: <P>
356: The C++ wrapper was contributed by Google Inc.
357: <br>
358: Copyright © 2007 Google Inc.
359: <br>
360: </P>
361: <br><a name="SEC12" href="#TOC1">REVISION</a><br>
362: <P>
363: Last updated: 17 March 2009
364: <br>
365: Minor typo fixed: 25 July 2011
366: <br>
367: <p>
368: Return to the <a href="index.html">PCRE index page</a>.
369: </p>
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