C++ Regex Library - regex_search

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Description

It returns whether some sub-sequence in the target sequence (the subject) matches the regular expression rgx (the pattern). The target sequence is either s or the character sequence between first and last, depending on the version used.

Declaration

Following is the declaration for std::regex_search.

template <class charT, class traits>
   bool regex_search (const charT* s, const basic_regex<charT,traits>& rgx,
   regex_constants::match_flag_type flags = regex_constants::match_default);

C++11

template <class charT, class traits>
   bool regex_search (const charT* s, const basic_regex<charT,traits>& rgx,
   regex_constants::match_flag_type flags = regex_constants::match_default);

C++14

template <class charT, class traits>
  bool regex_search (const charT* s, const basic_regex<charT,traits>& rgx,
          regex_constants::match_flag_type flags = regex_constants::match_default);

Parameters

• s − It is a string with the target sequence.

• rgx − It is a basic_regex object to match.

• flags − It is used to control how rgx is matched.

• m − It is an object of a match_results type.

Return Value

It returns true if rgx matches against a sub-sequence in the target sequence. false otherwise.

Exceptions

No-noexcept − this member function never throws exceptions.

Example

In below example for std::regex_search.

#include <iostream>
#include <string>
#include <regex>

int main () {
   std::string s ("this subject has a submarine as a subsequence");
   std::smatch m;
   std::regex e ("\\b(sub)([^ ]*)");

   std::cout << "Target sequence: " << s << std::endl;
   std::cout << "Regular expression: /\\b(sub)([^ ]*)/" << std::endl;
   std::cout << "The following matches and submatches were found:" << std::endl;

   while (std::regex_search (s,m,e)) {
      for (auto x:m) std::cout << x << " ";
      std::cout << std::endl;
      s = m.suffix().str();
   }

   return 0;
}

The output should be like this −

Target sequence: this subject has a submarine as a subsequence
Regular expression: /\b(sub)([^ ]*)/
The following matches and submatches were found:
subject sub ject 
submarine sub marine 
subsequence sub sequence