判断文件是否包含某种后缀名

#include <string>
#include <iostream>

bool has_suffix( const std::string& filename, const std::string& suffix ) 
{
  std::size_t index = filename.find( suffix, filename.size( ) - suffix.size( ) );
  return ( index != std::string::npos );
}
int main( )
{
    std::cout << has_suffix( "file.txt", ".txt" );
}