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std::regex_search(3) C++ Standard Libary std::regex_search(3) NAME std::regex_search - std::regex_search Synopsis Defined in header <regex> template< class BidirIt, class Alloc, class CharT, class Traits > bool regex_search( 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 CharT, class Alloc, class Traits > bool regex_search( const CharT* str, std::match_results<const CharT*,Alloc>& m, (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 STraits, class SAlloc, class Alloc, class CharT, class Traits > bool regex_search( const std::basic_string<CharT,STraits,SAlloc>& s, std::match_results< typename std::basic_string<CharT,STraits,SAlloc>::const_iterator, (3) (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 BidirIt, class CharT, class Traits > bool regex_search( BidirIt first, BidirIt last, (4) (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 Traits > bool regex_search( 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_search( 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_search( 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 there is a match between the regular expression e and some subsequence in the target character sequence. 1) Analyzes generic range [first,last). Match results are returned in m. 2) Analyzes a null-terminated string pointed to by str. Match re- sults are returned in m. 3) Analyzes a string s. Match results are returned in m. 4-6) Equivalent to (1-3), just omits the match results. 7) The overload (3) is prohibited from accepting temporary strings, otherwise this function populates match_results m with string iterators that become invalid immediately. regex_search will successfully match any subsequence of the given sequence, whereas std::regex_match will only return true if the regular expression matches the entire sequence. Parameters first, last - a range identifying the target character sequence str - a pointer to a null-terminated target character se- quence s - a string identifying target character sequence e - the std::regex that should be applied to the target character sequence m - the match results flags - std::regex_constants::match_flag_type governing search behavior Type requirements - BidirIt must meet the requirements of LegacyBidirectionalIterator. - Alloc must meet the requirements of Allocator. 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 m[0].first m.prefix().matched m.prefix().first != m.prefix().second m.suffix().first m[0].second m.suffix().second last m.suffix().matched m.suffix().first != m.suffix().second m[0].first the start of the matching sequence m[0].second the end of the matching sequence m[0].matched true 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 In order to examine all matches within the target sequence, std::regex_search may be called in a loop, restarting each time from m[0].second of the pre- vious call. std::regex_iterator offers an easy interface to this iteration. Example // Run this code #include <iostream> #include <string> #include <regex> int main() { std::string lines[] = {"Roses are #ff0000", "violets are #0000ff", "all of my base are belong to you"}; std::regex color_regex("#([a-f0-9]{2})" "([a-f0-9]{2})" "([a-f0-9]{2})"); // simple match for (const auto &line : lines) { std::cout << line << ": " << std::boolalpha << std::regex_search(line, color_regex) << '\n'; } std::cout << '\n'; // show contents of marked subexpressions within each match std::smatch color_match; for (const auto& line : lines) { if(std::regex_search(line, color_match, color_regex)) { std::cout << "matches for '" << line << "'\n"; std::cout << "Prefix: '" << color_match.prefix() << "'\n"; for (size_t i = 0; i < color_match.size(); ++i) std::cout << i << ": " << color_match[i] << '\n'; std::cout << "Suffix: '" << color_match.suffix() << "\'\n\n"; } } // repeated search (see also std::regex_iterator) std::string log(R"( Speed: 366 Mass: 35 Speed: 378 Mass: 32 Speed: 400 Mass: 30)"); std::regex r(R"(Speed:\t\d*)"); std::smatch sm; while(regex_search(log, sm, r)) { std::cout << sm.str() << '\n'; log = sm.suffix(); } // C-style string demo std::cmatch cm; if(std::regex_search("this is a test", cm, std::regex("test"))) std::cout << "\nFound " << cm[0] << " at position " << cm.pre- fix().length(); } Output: Roses are #ff0000: true violets are #0000ff: true all of my base are belong to you: false matches for 'Roses are #ff0000' Prefix: 'Roses are ' 0: #ff0000 1: ff 2: 00 3: 00 Suffix: '' matches for 'violets are #0000ff' Prefix: 'violets are ' 0: #0000ff 1: 00 2: 00 3: ff Suffix: '' Speed: 366 Speed: 378 Speed: 400 Found test at position 10 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_match attempts to match a regular expression to an entire character sequence (C++11) (function template) http://cppreference.com 2022.07.31 std::regex_search(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Notes | Example | Output: | See also
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