std::basic_string<CharT,Traits,Allocator>::substr (3) - Linux Man Pages

std::basic_string<CharT,Traits,Allocator>::substr: std::basic_string<CharT,Traits,Allocator>::substr

NAME

std::basic_string<CharT,Traits,Allocator>::substr - std::basic_string<CharT,Traits,Allocator>::substr

Synopsis


basic_string substr( size_type pos = 0,
size_type count = npos ) const;


Returns a substring [pos, pos+count). If the requested substring extends past the end of the string, or if count == npos, the returned substring is [pos,size()).

Parameters


pos - position of the first character to include
count - length of the substring

Return value


String containing the substring [pos, pos+count).

Exceptions


std::out_of_range if pos >size()

Complexity


Linear in count

Notes


The returned string is constructed as if by basic_string(data()+pos, count), which implies that the returned string's allocator will be default-constructed — the new allocator will not be a copy of this->get_allocator().

Example


// Run this code


  #include <string>
  #include <iostream>


  int main()
  {
      std::string a = "0123456789abcdefghij";


      // count is npos, returns [pos, size())
      std::string sub1 = a.substr(10);
      std::cout << sub1 << '\n';


      // both pos and pos+count are within bounds, returns [pos, pos+count)
      std::string sub2 = a.substr(5, 3);
      std::cout << sub2 << '\n';


      // pos is within bounds, pos+count is not, returns [pos, size())
      std::string sub4 = a.substr(a.size()-3, 50);
      std::cout << sub4 << '\n';


      try {
          // pos is out of bounds, throws
          std::string sub5 = a.substr(a.size()+3, 50);
          std::cout << sub5 << '\n';
      } catch(const std::out_of_range& e) {
          std::cout << "pos exceeds string size\n";
      }
  }

Output:


  abcdefghij
  567
  hij
  pos exceeds string size

See also


       copies characters
copy (public member function)
       returns the number of characters
size (public member function)
length
       find characters in the string
find (public member function)