+Return to the PCRE index page. +
+
+This page is part of the PCRE HTML documentation. It was generated automatically
+from the original man page. If there is any nonsense in it, please consult the
+man page, in case the conversion went wrong.
+
+
+#include <pcrecpp.h> +
++The C++ wrapper for PCRE was provided by Google Inc. Some additional +functionality was added by Giuseppe Maxia. This brief man page was constructed +from the notes in the pcrecpp.h file, which should be consulted for +further details. +
++The "FullMatch" operation checks that supplied text matches a supplied pattern +exactly. If pointer arguments are supplied, it copies matched sub-strings that +match sub-patterns into them. +
+ Example: successful match
+ pcrecpp::RE re("h.*o");
+ re.FullMatch("hello");
+
+ Example: unsuccessful match (requires full match):
+ pcrecpp::RE re("e");
+ !re.FullMatch("hello");
+
+ Example: creating a temporary RE object:
+ pcrecpp::RE("h.*o").FullMatch("hello");
+
+You can pass in a "const char*" or a "string" for "text". The examples below
+tend to use a const char*. You can, as in the different examples above, store
+the RE object explicitly in a variable or use a temporary RE object. The
+examples below use one mode or the other arbitrarily. Either could correctly be
+used for any of these examples.
+
++You must supply extra pointer arguments to extract matched subpieces. +
+ Example: extracts "ruby" into "s" and 1234 into "i"
+ int i;
+ string s;
+ pcrecpp::RE re("(\\w+):(\\d+)");
+ re.FullMatch("ruby:1234", &s, &i);
+
+ Example: does not try to extract any extra sub-patterns
+ re.FullMatch("ruby:1234", &s);
+
+ Example: does not try to extract into NULL
+ re.FullMatch("ruby:1234", NULL, &i);
+
+ Example: integer overflow causes failure
+ !re.FullMatch("ruby:1234567891234", NULL, &i);
+
+ Example: fails because there aren't enough sub-patterns:
+ !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
+
+ Example: fails because string cannot be stored in integer
+ !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
+
+The provided pointer arguments can be pointers to any scalar numeric
+type, or one of:
++ string (matched piece is copied to string) + StringPiece (StringPiece is mutated to point to matched piece) + T (where "bool T::ParseFrom(const char*, int)" exists) + NULL (the corresponding matched sub-pattern is not copied) ++The function returns true iff all of the following conditions are satisfied: +
+ a. "text" matches "pattern" exactly; + + b. The number of matched sub-patterns is >= number of supplied + pointers; + + c. The "i"th argument has a suitable type for holding the + string captured as the "i"th sub-pattern. If you pass in + void * NULL for the "i"th argument, or a non-void * NULL + of the correct type, or pass fewer arguments than the + number of sub-patterns, "i"th captured sub-pattern is + ignored. ++CAVEAT: An optional sub-pattern that does not exist in the matched +string is assigned the empty string. Therefore, the following will +return false (because the empty string is not a valid number): +
+ int number;
+ pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
+
+The matching interface supports at most 16 arguments per call.
+If you need more, consider using the more general interface
+pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for
+DoMatch.
+
++You can use the "QuoteMeta" operation to insert backslashes before all +potentially meaningful characters in a string. The returned string, used as a +regular expression, will exactly match the original string. +
+ Example: + string quoted = RE::QuoteMeta(unquoted); ++Note that it's legal to escape a character even if it has no special meaning in +a regular expression -- so this function does that. (This also makes it +identical to the perl function of the same name; see "perldoc -f quotemeta".) +For example, "1.5-2.0?" becomes "1\.5\-2\.0\?". + +
+You can use the "PartialMatch" operation when you want the pattern +to match any substring of the text. +
+ Example: simple search for a string:
+ pcrecpp::RE("ell").PartialMatch("hello");
+
+ Example: find first number in a string:
+ int number;
+ pcrecpp::RE re("(\\d+)");
+ re.PartialMatch("x*100 + 20", &number);
+ assert(number == 100);
+
+
++By default, pattern and text are plain text, one byte per character. The UTF8 +flag, passed to the constructor, causes both pattern and string to be treated +as UTF-8 text, still a byte stream but potentially multiple bytes per +character. In practice, the text is likelier to be UTF-8 than the pattern, but +the match returned may depend on the UTF8 flag, so always use it when matching +UTF8 text. For example, "." will match one byte normally but with UTF8 set may +match up to three bytes of a multi-byte character. +
+ Example: + pcrecpp::RE_Options options; + options.set_utf8(); + pcrecpp::RE re(utf8_pattern, options); + re.FullMatch(utf8_string); + + Example: using the convenience function UTF8(): + pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8()); + re.FullMatch(utf8_string); ++NOTE: The UTF8 flag is ignored if pcre was not configured with the +
+ --enable-utf8 flag. ++ +
+PCRE defines some modifiers to change the behavior of the regular expression +engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to +pass such modifiers to a RE class. Currently, the following modifiers are +supported: +
+ modifier description Perl corresponding + + PCRE_CASELESS case insensitive match /i + PCRE_MULTILINE multiple lines match /m + PCRE_DOTALL dot matches newlines /s + PCRE_DOLLAR_ENDONLY $ matches only at end N/A + PCRE_EXTRA strict escape parsing N/A + PCRE_EXTENDED ignore whitespaces /x + PCRE_UTF8 handles UTF8 chars built-in + PCRE_UNGREEDY reverses * and *? N/A + PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*) ++(*) Both Perl and PCRE allow non capturing parentheses by means of the +"?:" modifier within the pattern itself. e.g. (?:ab|cd) does not +capture, while (ab|cd) does. + +
+For a full account on how each modifier works, please check the +PCRE API reference page. +
++For each modifier, there are two member functions whose name is made +out of the modifier in lowercase, without the "PCRE_" prefix. For +instance, PCRE_CASELESS is handled by +
+ bool caseless() ++which returns true if the modifier is set, and +
+ RE_Options & set_caseless(bool) ++which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be +accessed through the set_match_limit() and match_limit() member +functions. Setting match_limit to a non-zero value will limit the +execution of pcre to keep it from doing bad things like blowing the stack or +taking an eternity to return a result. A value of 5000 is good enough to stop +stack blowup in a 2MB thread stack. Setting match_limit to zero disables +match limiting. Alternatively, you can call match_limit_recursion() +which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE +recurses. match_limit() limits the number of matches PCRE does; +match_limit_recursion() limits the depth of internal recursion, and +therefore the amount of stack that is used. + +
+Normally, to pass one or more modifiers to a RE class, you declare +a RE_Options object, set the appropriate options, and pass this +object to a RE constructor. Example: +
+ RE_options opt;
+ opt.set_caseless(true);
+ if (RE("HELLO", opt).PartialMatch("hello world")) ...
+
+RE_options has two constructors. The default constructor takes no arguments and
+creates a set of flags that are off by default. The optional parameter
+option_flags is to facilitate transfer of legacy code from C programs.
+This lets you do
++ RE(pattern, + RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str); ++However, new code is better off doing +
+ RE(pattern, + RE_Options().set_caseless(true).set_multiline(true)) + .PartialMatch(str); ++If you are going to pass one of the most used modifiers, there are some +convenience functions that return a RE_Options class with the +appropriate modifier already set: CASELESS(), UTF8(), +MULTILINE(), DOTALL(), and EXTENDED(). + +
+If you need to set several options at once, and you don't want to go through +the pains of declaring a RE_Options object and setting several options, there +is a parallel method that give you such ability on the fly. You can concatenate +several set_xxxxx() member functions, since each of them returns a +reference to its class object. For example, to pass PCRE_CASELESS, +PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write: +
+ RE(" ^ xyz \\s+ .* blah$",
+ RE_Options()
+ .set_caseless(true)
+ .set_extended(true)
+ .set_multiline(true)).PartialMatch(sometext);
+
+
+
++The "Consume" operation may be useful if you want to repeatedly +match regular expressions at the front of a string and skip over +them as they match. This requires use of the "StringPiece" type, +which represents a sub-range of a real string. Like RE, StringPiece +is defined in the pcrecpp namespace. +
+ Example: read lines of the form "var = value" from a string. + string contents = ...; // Fill string somehow + pcrecpp::StringPiece input(contents); // Wrap in a StringPiece ++ +
+
+ string var;
+ int value;
+ pcrecpp::RE re("(\\w+) = (\\d+)\n");
+ while (re.Consume(&input, &var, &value)) {
+ ...;
+ }
+
+Each successful call to "Consume" will set "var/value", and also
+advance "input" so it points past the matched text.
+
++The "FindAndConsume" operation is similar to "Consume" but does not +anchor your match at the beginning of the string. For example, you +could extract all words from a string by repeatedly calling +
+ pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
+
+
++By default, if you pass a pointer to a numeric value, the +corresponding text is interpreted as a base-10 number. You can +instead wrap the pointer with a call to one of the operators Hex(), +Octal(), or CRadix() to interpret the text in another base. The +CRadix operator interprets C-style "0" (base-8) and "0x" (base-16) +prefixes, but defaults to base-10. +
+ Example:
+ int a, b, c, d;
+ pcrecpp::RE re("(.*) (.*) (.*) (.*)");
+ re.FullMatch("100 40 0100 0x40",
+ pcrecpp::Octal(&a), pcrecpp::Hex(&b),
+ pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
+
+will leave 64 in a, b, c, and d.
+
++You can replace the first match of "pattern" in "str" with "rewrite". +Within "rewrite", backslash-escaped digits (\1 to \9) can be +used to insert text matching corresponding parenthesized group +from the pattern. \0 in "rewrite" refers to the entire matching +text. For example: +
+ string s = "yabba dabba doo";
+ pcrecpp::RE("b+").Replace("d", &s);
+
+will leave "s" containing "yada dabba doo". The result is true if the pattern
+matches and a replacement occurs, false otherwise.
+
++GlobalReplace is like Replace except that it replaces all +occurrences of the pattern in the string with the rewrite. Replacements are +not subject to re-matching. For example: +
+ string s = "yabba dabba doo";
+ pcrecpp::RE("b+").GlobalReplace("d", &s);
+
+will leave "s" containing "yada dada doo". It returns the number of
+replacements made.
+
++Extract is like Replace, except that if the pattern matches, +"rewrite" is copied into "out" (an additional argument) with substitutions. +The non-matching portions of "text" are ignored. Returns true iff a match +occurred and the extraction happened successfully; if no match occurs, the +string is left unaffected. +
+
+The C++ wrapper was contributed by Google Inc.
+
+Copyright © 2007 Google Inc.
+
+
+Last updated: 12 November 2007
+
+
+Return to the PCRE index page. +