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 results 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 sequence
   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 previous 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.prefix().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 retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
                       basic_string rvalues were accepted, which rejected via a deleted
   LWG 2329 C++11 was likely to result in dangling overload
                       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)