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1 .TH PCRECPP 3
2 .SH NAME
3 PCRE - Perl-compatible regular expressions.
4 .SH "SYNOPSIS OF C++ WRAPPER"
5 .rs
6 .sp
7 .B #include <pcrecpp.h>
8 .
9 .SH DESCRIPTION
10 .rs
11 .sp
12 The C++ wrapper for PCRE was provided by Google Inc. Some additional
13 functionality was added by Giuseppe Maxia. This brief man page was constructed
14 from the notes in the \fIpcrecpp.h\fP file, which should be consulted for
15 further details.
16 .
17 .
18 .SH "MATCHING INTERFACE"
19 .rs
20 .sp
21 The "FullMatch" operation checks that supplied text matches a supplied pattern
22 exactly. If pointer arguments are supplied, it copies matched sub-strings that
23 match sub-patterns into them.
24 .sp
25 Example: successful match
26 pcrecpp::RE re("h.*o");
27 re.FullMatch("hello");
28 .sp
29 Example: unsuccessful match (requires full match):
30 pcrecpp::RE re("e");
31 !re.FullMatch("hello");
32 .sp
33 Example: creating a temporary RE object:
34 pcrecpp::RE("h.*o").FullMatch("hello");
35 .sp
36 You can pass in a "const char*" or a "string" for "text". The examples below
37 tend to use a const char*. You can, as in the different examples above, store
38 the RE object explicitly in a variable or use a temporary RE object. The
39 examples below use one mode or the other arbitrarily. Either could correctly be
40 used for any of these examples.
41 .P
42 You must supply extra pointer arguments to extract matched subpieces.
43 .sp
44 Example: extracts "ruby" into "s" and 1234 into "i"
45 int i;
46 string s;
47 pcrecpp::RE re("(\e\ew+):(\e\ed+)");
48 re.FullMatch("ruby:1234", &s, &i);
49 .sp
50 Example: does not try to extract any extra sub-patterns
51 re.FullMatch("ruby:1234", &s);
52 .sp
53 Example: does not try to extract into NULL
54 re.FullMatch("ruby:1234", NULL, &i);
55 .sp
56 Example: integer overflow causes failure
57 !re.FullMatch("ruby:1234567891234", NULL, &i);
58 .sp
59 Example: fails because there aren't enough sub-patterns:
60 !pcrecpp::RE("\e\ew+:\e\ed+").FullMatch("ruby:1234", &s);
61 .sp
62 Example: fails because string cannot be stored in integer
63 !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
64 .sp
65 The provided pointer arguments can be pointers to any scalar numeric
66 type, or one of:
67 .sp
68 string (matched piece is copied to string)
69 StringPiece (StringPiece is mutated to point to matched piece)
70 T (where "bool T::ParseFrom(const char*, int)" exists)
71 NULL (the corresponding matched sub-pattern is not copied)
72 .sp
73 The function returns true iff all of the following conditions are satisfied:
74 .sp
75 a. "text" matches "pattern" exactly;
76 .sp
77 b. The number of matched sub-patterns is >= number of supplied
78 pointers;
79 .sp
80 c. The "i"th argument has a suitable type for holding the
81 string captured as the "i"th sub-pattern. If you pass in
82 void * NULL for the "i"th argument, or a non-void * NULL
83 of the correct type, or pass fewer arguments than the
84 number of sub-patterns, "i"th captured sub-pattern is
85 ignored.
86 .sp
87 CAVEAT: An optional sub-pattern that does not exist in the matched
88 string is assigned the empty string. Therefore, the following will
89 return false (because the empty string is not a valid number):
90 .sp
91 int number;
92 pcrecpp::RE::FullMatch("abc", "[a-z]+(\e\ed+)?", &number);
93 .sp
94 The matching interface supports at most 16 arguments per call.
95 If you need more, consider using the more general interface
96 \fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
97 \fBDoMatch\fP.
98 .
99 .SH "QUOTING METACHARACTERS"
100 .rs
101 .sp
102 You can use the "QuoteMeta" operation to insert backslashes before all
103 potentially meaningful characters in a string. The returned string, used as a
104 regular expression, will exactly match the original string.
105 .sp
106 Example:
107 string quoted = RE::QuoteMeta(unquoted);
108 .sp
109 Note that it's legal to escape a character even if it has no special meaning in
110 a regular expression -- so this function does that. (This also makes it
111 identical to the perl function of the same name; see "perldoc -f quotemeta".)
112 For example, "1.5-2.0?" becomes "1\e.5\e-2\e.0\e?".
113 .
114 .SH "PARTIAL MATCHES"
115 .rs
116 .sp
117 You can use the "PartialMatch" operation when you want the pattern
118 to match any substring of the text.
119 .sp
120 Example: simple search for a string:
121 pcrecpp::RE("ell").PartialMatch("hello");
122 .sp
123 Example: find first number in a string:
124 int number;
125 pcrecpp::RE re("(\e\ed+)");
126 re.PartialMatch("x*100 + 20", &number);
127 assert(number == 100);
128 .
129 .
130 .SH "UTF-8 AND THE MATCHING INTERFACE"
131 .rs
132 .sp
133 By default, pattern and text are plain text, one byte per character. The UTF8
134 flag, passed to the constructor, causes both pattern and string to be treated
135 as UTF-8 text, still a byte stream but potentially multiple bytes per
136 character. In practice, the text is likelier to be UTF-8 than the pattern, but
137 the match returned may depend on the UTF8 flag, so always use it when matching
138 UTF8 text. For example, "." will match one byte normally but with UTF8 set may
139 match up to three bytes of a multi-byte character.
140 .sp
141 Example:
142 pcrecpp::RE_Options options;
143 options.set_utf8();
144 pcrecpp::RE re(utf8_pattern, options);
145 re.FullMatch(utf8_string);
146 .sp
147 Example: using the convenience function UTF8():
148 pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
149 re.FullMatch(utf8_string);
150 .sp
151 NOTE: The UTF8 flag is ignored if pcre was not configured with the
152 --enable-utf8 flag.
153 .
154 .
155 .SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE"
156 .rs
157 .sp
158 PCRE defines some modifiers to change the behavior of the regular expression
159 engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
160 pass such modifiers to a RE class. Currently, the following modifiers are
161 supported:
162 .sp
163 modifier description Perl corresponding
164 .sp
165 PCRE_CASELESS case insensitive match /i
166 PCRE_MULTILINE multiple lines match /m
167 PCRE_DOTALL dot matches newlines /s
168 PCRE_DOLLAR_ENDONLY $ matches only at end N/A
169 PCRE_EXTRA strict escape parsing N/A
170 PCRE_EXTENDED ignore whitespaces /x
171 PCRE_UTF8 handles UTF8 chars built-in
172 PCRE_UNGREEDY reverses * and *? N/A
173 PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
174 .sp
175 (*) Both Perl and PCRE allow non capturing parentheses by means of the
176 "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
177 capture, while (ab|cd) does.
178 .P
179 For a full account on how each modifier works, please check the
180 PCRE API reference page.
181 .P
182 For each modifier, there are two member functions whose name is made
183 out of the modifier in lowercase, without the "PCRE_" prefix. For
184 instance, PCRE_CASELESS is handled by
185 .sp
186 bool caseless()
187 .sp
188 which returns true if the modifier is set, and
189 .sp
190 RE_Options & set_caseless(bool)
191 .sp
192 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
193 accessed through the \fBset_match_limit()\fR and \fBmatch_limit()\fR member
194 functions. Setting \fImatch_limit\fR to a non-zero value will limit the
195 execution of pcre to keep it from doing bad things like blowing the stack or
196 taking an eternity to return a result. A value of 5000 is good enough to stop
197 stack blowup in a 2MB thread stack. Setting \fImatch_limit\fR to zero disables
198 match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP
199 which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
200 recurses. \fBmatch_limit()\fP limits the number of matches PCRE does;
201 \fBmatch_limit_recursion()\fP limits the depth of internal recursion, and
202 therefore the amount of stack that is used.
203 .P
204 Normally, to pass one or more modifiers to a RE class, you declare
205 a \fIRE_Options\fR object, set the appropriate options, and pass this
206 object to a RE constructor. Example:
207 .sp
208 RE_options opt;
209 opt.set_caseless(true);
210 if (RE("HELLO", opt).PartialMatch("hello world")) ...
211 .sp
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 \fIoption_flags\fR is to facilitate transfer of legacy code from C programs.
215 This lets you do
216 .sp
217 RE(pattern,
218 RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
219 .sp
220 However, new code is better off doing
221 .sp
222 RE(pattern,
223 RE_Options().set_caseless(true).set_multiline(true))
224 .PartialMatch(str);
225 .sp
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: \fBCASELESS()\fR, \fBUTF8()\fR,
229 \fBMULTILINE()\fR, \fBDOTALL\fR(), and \fBEXTENDED()\fR.
230 .P
231 If you need to set several options at once, and you don't want to go through
232 the pains of declaring a RE_Options object and setting several options, there
233 is a parallel method that give you such ability on the fly. You can concatenate
234 several \fBset_xxxxx()\fR member functions, since each of them returns a
235 reference to its class object. For example, to pass PCRE_CASELESS,
236 PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
237 .sp
238 RE(" ^ xyz \e\es+ .* blah$",
239 RE_Options()
240 .set_caseless(true)
241 .set_extended(true)
242 .set_multiline(true)).PartialMatch(sometext);
243 .sp
244 .
245 .
246 .SH "SCANNING TEXT INCREMENTALLY"
247 .rs
248 .sp
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 .sp
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
259 string var;
260 int value;
261 pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en");
262 while (re.Consume(&input, &var, &value)) {
263 ...;
264 }
265 .sp
266 Each successful call to "Consume" will set "var/value", and also
267 advance "input" so it points past the matched text.
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 .sp
273 pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word)
274 .
275 .
276 .SH "PARSING HEX/OCTAL/C-RADIX NUMBERS"
277 .rs
278 .sp
279 By default, if you pass a pointer to a numeric value, the
280 corresponding text is interpreted as a base-10 number. You can
281 instead wrap the pointer with a call to one of the operators Hex(),
282 Octal(), or CRadix() to interpret the text in another base. The
283 CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
284 prefixes, but defaults to base-10.
285 .sp
286 Example:
287 int a, b, c, d;
288 pcrecpp::RE re("(.*) (.*) (.*) (.*)");
289 re.FullMatch("100 40 0100 0x40",
290 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
291 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
292 .sp
293 will leave 64 in a, b, c, and d.
294 .
295 .
296 .SH "REPLACING PARTS OF STRINGS"
297 .rs
298 .sp
299 You can replace the first match of "pattern" in "str" with "rewrite".
300 Within "rewrite", backslash-escaped digits (\e1 to \e9) can be
301 used to insert text matching corresponding parenthesized group
302 from the pattern. \e0 in "rewrite" refers to the entire matching
303 text. For example:
304 .sp
305 string s = "yabba dabba doo";
306 pcrecpp::RE("b+").Replace("d", &s);
307 .sp
308 will leave "s" containing "yada dabba doo". The result is true if the pattern
309 matches and a replacement occurs, false otherwise.
310 .P
311 \fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all
312 occurrences of the pattern in the string with the rewrite. Replacements are
313 not subject to re-matching. For example:
314 .sp
315 string s = "yabba dabba doo";
316 pcrecpp::RE("b+").GlobalReplace("d", &s);
317 .sp
318 will leave "s" containing "yada dada doo". It returns the number of
319 replacements made.
320 .P
321 \fBExtract\fP is like \fBReplace\fP, except that if the pattern matches,
322 "rewrite" is copied into "out" (an additional argument) with substitutions.
323 The non-matching portions of "text" are ignored. Returns true iff a match
324 occurred and the extraction happened successfully; if no match occurs, the
325 string is left unaffected.
326 .
327 .
328 .SH AUTHOR
329 .rs
330 .sp
331 .nf
332 The C++ wrapper was contributed by Google Inc.
333 Copyright (c) 2007 Google Inc.
334 .fi
335 .
336 .
337 .SH REVISION
338 .rs
339 .sp
340 .nf
341 Last updated: 12 November 2007
342 .fi

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