cppreference.com > C++ Strings > find find Syntax:
      #include <string>
      size_type find( const string& str, size_type index );
      size_type find( const char* str, size_type index );
      size_type find( const char* str, size_type index, size_type length );
      size_type find( char ch, size_type index );
The function find() either: returns the first occurrence of str within the current string, starting at index, string::npos if nothing is found, returns the first occurrence of str within the current string and within length characters, starting at index, string::npos if nothing is found, or returns the index of the first occurrence ch within the current string, starting at index, string::npos if nothing is found. For example:
       string str1( "Alpha Beta Gamma Delta" );
       string::size_type loc = str1.find( "Omega", 0 );
       if( loc != string::npos )
         cout << "Found Omega at " << loc << endl;
       else
         cout << "Didn't find Omega" << endl;
Related topics: find_first_not_of find_first_of find_last_not_of find_last_of rfind