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1 nigel 79 .TH PCRECPP 3
2 nigel 77 .SH NAME
3     PCRE - Perl-compatible regular expressions.
4     .SH "SYNOPSIS OF C++ WRAPPER"
5     .rs
6     .sp
7     .B #include <pcrecpp.h>
8 ph10 99 .
9 nigel 77 .SH DESCRIPTION
10     .rs
11     .sp
12 nigel 81 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 nigel 77 .
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     NULL for the "i"th argument, or pass fewer arguments than
83     number of sub-patterns, "i"th captured sub-pattern is
84     ignored.
85     .sp
86 nigel 93 CAVEAT: An optional sub-pattern that does not exist in the matched
87     string is assigned the empty string. Therefore, the following will
88     return false (because the empty string is not a valid number):
89     .sp
90     int number;
91     pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
92     .sp
93 nigel 77 The matching interface supports at most 16 arguments per call.
94     If you need more, consider using the more general interface
95     \fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
96     \fBDoMatch\fP.
97     .
98 nigel 93 .SH "QUOTING METACHARACTERS"
99     .rs
100     .sp
101     You can use the "QuoteMeta" operation to insert backslashes before all
102     potentially meaningful characters in a string. The returned string, used as a
103     regular expression, will exactly match the original string.
104     .sp
105     Example:
106     string quoted = RE::QuoteMeta(unquoted);
107     .sp
108     Note that it's legal to escape a character even if it has no special meaning in
109     a regular expression -- so this function does that. (This also makes it
110     identical to the perl function of the same name; see "perldoc -f quotemeta".)
111     For example, "1.5-2.0?" becomes "1\e.5\e-2\e.0\e?".
112     .
113 nigel 77 .SH "PARTIAL MATCHES"
114     .rs
115     .sp
116     You can use the "PartialMatch" operation when you want the pattern
117     to match any substring of the text.
118     .sp
119     Example: simple search for a string:
120     pcrecpp::RE("ell").PartialMatch("hello");
121     .sp
122     Example: find first number in a string:
123     int number;
124     pcrecpp::RE re("(\e\ed+)");
125     re.PartialMatch("x*100 + 20", &number);
126     assert(number == 100);
127     .
128     .
129     .SH "UTF-8 AND THE MATCHING INTERFACE"
130     .rs
131     .sp
132     By default, pattern and text are plain text, one byte per character. The UTF8
133     flag, passed to the constructor, causes both pattern and string to be treated
134     as UTF-8 text, still a byte stream but potentially multiple bytes per
135     character. In practice, the text is likelier to be UTF-8 than the pattern, but
136     the match returned may depend on the UTF8 flag, so always use it when matching
137     UTF8 text. For example, "." will match one byte normally but with UTF8 set may
138     match up to three bytes of a multi-byte character.
139     .sp
140     Example:
141     pcrecpp::RE_Options options;
142     options.set_utf8();
143     pcrecpp::RE re(utf8_pattern, options);
144     re.FullMatch(utf8_string);
145     .sp
146     Example: using the convenience function UTF8():
147     pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
148     re.FullMatch(utf8_string);
149     .sp
150     NOTE: The UTF8 flag is ignored if pcre was not configured with the
151     --enable-utf8 flag.
152     .
153     .
154 nigel 81 .SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE"
155     .rs
156     .sp
157     PCRE defines some modifiers to change the behavior of the regular expression
158     engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
159     pass such modifiers to a RE class. Currently, the following modifiers are
160     supported:
161     .sp
162     modifier description Perl corresponding
163     .sp
164     PCRE_CASELESS case insensitive match /i
165     PCRE_MULTILINE multiple lines match /m
166     PCRE_DOTALL dot matches newlines /s
167     PCRE_DOLLAR_ENDONLY $ matches only at end N/A
168     PCRE_EXTRA strict escape parsing N/A
169     PCRE_EXTENDED ignore whitespaces /x
170     PCRE_UTF8 handles UTF8 chars built-in
171     PCRE_UNGREEDY reverses * and *? N/A
172     PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
173     .sp
174     (*) Both Perl and PCRE allow non capturing parentheses by means of the
175     "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
176     capture, while (ab|cd) does.
177     .P
178     For a full account on how each modifier works, please check the
179     PCRE API reference page.
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     .sp
185     bool caseless()
186     .sp
187     which returns true if the modifier is set, and
188     .sp
189     RE_Options & set_caseless(bool)
190     .sp
191 nigel 87 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
192 nigel 81 accessed through the \fBset_match_limit()\fR and \fBmatch_limit()\fR member
193     functions. Setting \fImatch_limit\fR 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 \fImatch_limit\fR to zero disables
197 nigel 87 match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP
198     which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
199     recurses. \fBmatch_limit()\fP limits the number of matches PCRE does;
200     \fBmatch_limit_recursion()\fP limits the depth of internal recursion, and
201     therefore the amount of stack that is used.
202 nigel 81 .P
203     Normally, to pass one or more modifiers to a RE class, you declare
204     a \fIRE_Options\fR object, set the appropriate options, and pass this
205     object to a RE constructor. Example:
206     .sp
207     RE_options opt;
208     opt.set_caseless(true);
209     if (RE("HELLO", opt).PartialMatch("hello world")) ...
210     .sp
211     RE_options has two constructors. The default constructor takes no arguments and
212     creates a set of flags that are off by default. The optional parameter
213     \fIoption_flags\fR is to facilitate transfer of legacy code from C programs.
214     This lets you do
215     .sp
216     RE(pattern,
217     RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
218     .sp
219     However, new code is better off doing
220     .sp
221     RE(pattern,
222     RE_Options().set_caseless(true).set_multiline(true))
223     .PartialMatch(str);
224     .sp
225     If you are going to pass one of the most used modifiers, there are some
226     convenience functions that return a RE_Options class with the
227     appropriate modifier already set: \fBCASELESS()\fR, \fBUTF8()\fR,
228     \fBMULTILINE()\fR, \fBDOTALL\fR(), and \fBEXTENDED()\fR.
229     .P
230     If you need to set several options at once, and you don't want to go through
231     the pains of declaring a RE_Options object and setting several options, there
232     is a parallel method that give you such ability on the fly. You can concatenate
233     several \fBset_xxxxx()\fR member functions, since each of them returns a
234     reference to its class object. For example, to pass PCRE_CASELESS,
235     PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
236     .sp
237     RE(" ^ xyz \e\es+ .* blah$",
238     RE_Options()
239     .set_caseless(true)
240     .set_extended(true)
241     .set_multiline(true)).PartialMatch(sometext);
242     .sp
243     .
244     .
245 nigel 77 .SH "SCANNING TEXT INCREMENTALLY"
246     .rs
247     .sp
248     The "Consume" operation may be useful if you want to repeatedly
249     match regular expressions at the front of a string and skip over
250     them as they match. This requires use of the "StringPiece" type,
251     which represents a sub-range of a real string. Like RE, StringPiece
252     is defined in the pcrecpp namespace.
253     .sp
254     Example: read lines of the form "var = value" from a string.
255     string contents = ...; // Fill string somehow
256     pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
257    
258     string var;
259     int value;
260     pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en");
261     while (re.Consume(&input, &var, &value)) {
262     ...;
263     }
264     .sp
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     The "FindAndConsume" operation is similar to "Consume" but does not
269     anchor your match at the beginning of the string. For example, you
270     could extract all words from a string by repeatedly calling
271     .sp
272     pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word)
273     .
274     .
275     .SH "PARSING HEX/OCTAL/C-RADIX NUMBERS"
276     .rs
277     .sp
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     .sp
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     .sp
292     will leave 64 in a, b, c, and d.
293     .
294     .
295     .SH "REPLACING PARTS OF STRINGS"
296     .rs
297     .sp
298     You can replace the first match of "pattern" in "str" with "rewrite".
299     Within "rewrite", backslash-escaped digits (\e1 to \e9) can be
300     used to insert text matching corresponding parenthesized group
301     from the pattern. \e0 in "rewrite" refers to the entire matching
302     text. For example:
303     .sp
304     string s = "yabba dabba doo";
305     pcrecpp::RE("b+").Replace("d", &s);
306     .sp
307     will leave "s" containing "yada dabba doo". The result is true if the pattern
308     matches and a replacement occurs, false otherwise.
309     .P
310     \fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all
311     occurrences of the pattern in the string with the rewrite. Replacements are
312     not subject to re-matching. For example:
313     .sp
314     string s = "yabba dabba doo";
315     pcrecpp::RE("b+").GlobalReplace("d", &s);
316     .sp
317     will leave "s" containing "yada dada doo". It returns the number of
318     replacements made.
319     .P
320     \fBExtract\fP is like \fBReplace\fP, 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     .
326     .
327     .SH AUTHOR
328     .rs
329     .sp
330 ph10 99 .nf
331 nigel 77 The C++ wrapper was contributed by Google Inc.
332 ph10 117 Copyright (c) 2007 Google Inc.
333 ph10 99 .fi
334     .
335     .
336     .SH REVISION
337     .rs
338     .sp
339     .nf
340     Last updated: 06 March 2007
341     .fi

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