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OpenSolaris 2009.06 - man page for pcrecpp (opensolaris section 3)

PCRECPP(3)			     Library Functions Manual			       PCRECPP(3)

       PCRE - Perl-compatible regular expressions.


       #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

	 Example: successful match
	    pcrecpp::RE re("h.*o");

	 Example: unsuccessful match (requires full match):
	    pcrecpp::RE re("e");

	 Example: creating a temporary RE object:

       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

	 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

       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


       You can use the "QuoteMeta" operation to insert backslashes before all  potentially  mean-
       ingful  characters  in  a  string. The returned string, used as a regular expression, will
       exactly match the original string.

	    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 func-
       tion of the same name; see "perldoc  -f	quotemeta".)   For  example,  "1.5-2.0?"  becomes


       You  can use the "PartialMatch" operation when you want the pattern to match any substring
       of the text.

	 Example: simple search for a string:

	 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  like-
       lier  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.

	    pcrecpp::RE_Options options;
	    pcrecpp::RE re(utf8_pattern, options);

	 Example: using the convenience function UTF8():
	    pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());

       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  recur-
       sion, 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;
	  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


       However, new code is better off doing


       If you are going to pass one of the most used modifiers, there are some convenience  func-
       tions  that  return  a  RE_Options  class with the appropriate modifier already set: CASE-
       LESS(), 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  func-
       tions,  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

	  RE(" ^ xyz \\s+ .* blah$",


       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 inter-
       preted 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

	   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 (c) 2007 Google Inc.


       Last updated: 12 November 2007

       See attributes(5) for descriptions of the following attributes:

       |Availability	    | SUNWpcre	      |
       |Interface Stability | Uncommitted     |
       Source for PCRE is available on http://opensolaris.org.


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