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std::regex_match(3) C++ Standard Libary std::regex_match(3) NAME std::regex_match - std::regex_match Synopsis Defined in header <regex> template< class BidirIt, class Alloc, class CharT, class Traits > bool regex_match( BidirIt first, BidirIt last, (since std::match_results<BidirIt,Alloc>& m, (1) C++11) const std::basic_regex<CharT,Traits>& e, std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class BidirIt, class CharT, class Traits > bool regex_match( BidirIt first, BidirIt last, (2) (since const std::basic_regex<CharT,Traits>& e, C++11) std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class CharT, class Alloc, class Traits > bool regex_match( const CharT* str, std::match_results<const CharT*,Alloc>& m, (3) (since const std::basic_regex<CharT,Traits>& e, C++11) std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class STraits, class SAlloc, class Alloc, class CharT, class Traits > bool regex_match( const std::basic_string<CharT,STraits,SAlloc>& s, std::match_results< typename std::basic_string<CharT,STraits,SAlloc>::const_iterator, (4) (since Alloc C++11) >& m, const std::basic_regex<CharT,Traits>& e, std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class CharT, class Traits > bool regex_match( const CharT* str, (since const std::basic_regex<CharT,Traits>& e, (5) C++11) std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class STraits, class SAlloc, class CharT, class Traits > bool regex_match( const std::basic_string<CharT, STraits, SAlloc>& s, (6) (since const std::basic_regex<CharT,Traits>& e, C++11) std::regex_constants::match_flag_type flags = std::regex_constants::match_default ); template< class STraits, class SAlloc, class Alloc, class CharT, class Traits > bool regex_match( const std::basic_string<CharT,STraits,SAlloc>&&, std::match_results< typename std::basic_string<CharT,STraits,SAlloc>::const_iterator, (7) (since Alloc C++11) >&, const std::basic_regex<CharT,Traits>&, std::regex_constants::match_flag_type flags = std::regex_constants::match_default ) = delete; Determines if the regular expression e matches the entire target character sequence, which may be specified as std::string, a C-string, or an iterator pair. 1) Determines if there is a match between the regular expression e and the entire target character sequence [first,last), taking into account the ef- fect of flags. When determining if there is a match, only potential matches that match the entire character sequence are considered. Match results are returned in m. 2) Behaves as (1) above, omitting the match results. 3) Returns std::regex_match(str, str + std::char_traits<charT>::length(str), m, e, flags). 4) Returns std::regex_match(s.begin(), s.end(), m, e, flags). 5) Returns std::regex_match(str, str + std::char_traits<charT>::length(str), e, flags). 6) Returns std::regex_match(s.begin(), s.end(), e, flags). 7) The overload (4) is prohibited from accepting temporary strings, otherwise this function populates match_results m with string iterators that become invalid immediately. Note that regex_match will only successfully match a regular expres- sion to an entire character sequence, whereas std::regex_search will successfully match subsequences. Parameters first, last - the target character range to apply the regex to, given as iterators m - the match results str - the target string, given as a null-terminated C-style string s - the target string, given as a std::basic_string e - the regular expression flags - flags used to determine how the match will be per- formed Type requirements - BidirIt must meet the requirements of LegacyBidirectionalIterator. Return value Returns true if a match exists, false otherwise. In either case, the object m is updated, as follows: If the match does not exist: m.ready() == true m.empty() == true m.size() == 0 If the match exists: m.ready() true m.empty() false m.size() number of marked subexpressions plus 1, that is, 1+e.mark_count() m.prefix().first first m.prefix().second first m.prefix().matched false (the match prefix is empty) m.suffix().first last m.suffix().second last m.suffix().matched false (the match suffix is empty) m[0].first first m[0].second last m[0].matched true (the entire sequence is matched) m[n].first the start of the sequence that matched marked sub-expression n, or last if the subexpression did not participate in the match m[n].second the end of the sequence that matched marked sub- expression n, or last if the subexpression did not participate in the match m[n].matched true if sub-expression n participated in the match, false otherwise Notes Because regex_match only considers full matches, the same regex may give different matches between regex_match and std::regex_search: std::regex re("Get|GetValue"); std::cmatch m; std::regex_search("GetValue", m, re); // returns true, and m[0] con- tains "Get" std::regex_match ("GetValue", m, re); // returns true, and m[0] con- tains "GetValue" std::regex_search("GetValues", m, re); // returns true, and m[0] con- tains "Get" std::regex_match ("GetValues", m, re); // returns false Example // Run this code #include <iostream> #include <string> #include <regex> int main() { // Simple regular expression matching const std::string fnames[] = {"foo.txt", "bar.txt", "baz.dat", "zoidberg"}; const std::regex txt_regex("[a-z]+\\.txt"); for (const auto &fname : fnames) { std::cout << fname << ": " << std::regex_match(fname, txt_regex) << '\n'; } // Extraction of a sub-match const std::regex base_regex("([a-z]+)\\.txt"); std::smatch base_match; for (const auto &fname : fnames) { if (std::regex_match(fname, base_match, base_regex)) { // The first sub_match is the whole string; the next // sub_match is the first parenthesized expression. if (base_match.size() == 2) { std::ssub_match base_sub_match = base_match[1]; std::string base = base_sub_match.str(); std::cout << fname << " has a base of " << base << '\n'; } } } // Extraction of several sub-matches const std::regex pieces_regex("([a-z]+)\\.([a-z]+)"); std::smatch pieces_match; for (const auto &fname : fnames) { if (std::regex_match(fname, pieces_match, pieces_regex)) { std::cout << fname << '\n'; for (size_t i = 0; i < pieces_match.size(); ++i) { std::ssub_match sub_match = pieces_match[i]; std::string piece = sub_match.str(); std::cout << " submatch " << i << ": " << piece << '\n'; } } } } Output: foo.txt: 1 bar.txt: 1 baz.dat: 0 zoidberg: 0 foo.txt has a base of foo bar.txt has a base of bar foo.txt submatch 0: foo.txt submatch 1: foo submatch 2: txt bar.txt submatch 0: bar.txt submatch 1: bar submatch 2: txt baz.dat submatch 0: baz.dat submatch 1: baz submatch 2: dat Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior basic_string rvalues were accepted, which re- jected via a deleted LWG 2329 C++11 was likely to result in dangling over- load iterators See also basic_regex regular expression object (C++11) (class template) match_results identifies one regular expression match, including all sub-expression (C++11) matches (class template) regex_search attempts to match a regular expression to any part of a character (C++11) sequence (function template) http://cppreference.com 2022.07.31 std::regex_match(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Notes | Example | Output: | See also
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