C++: how to get the actual time with time and localtime?

Question

I\'m looking for a way to save the time in a HH::MM::SS fashion in C++. I saw here that they are many solutions and after a little research I opted for time and

Answer 1

localtime has what is best considered a legacy interface. It can't be used in multithreaded code, for example. In a multithreaded environment, you can use localtime_r under Posix or localtime_s under Windows. Otherwise, all you have to do is save the results:

tm then = *localtime( &t1 );
//  ...
tm now = *localtime( &t2 );

It would probably be more idiomatic, however, to only call localtime
immediately before formatting the output, e.g.:

std::string
timestampToString( time_t timeAndDate )
{
    char results[100];
    if ( strftime( results, sizeof( results ), "%Y-%m-%d, %H:%M:%S", 
                localtime( &timeAndDate) ) == 0 ) {
        assert( 0 );
    }
    return results;
}

and then writing:

std::cout << formatTime( t1 ) << std::endl;

(You could also create a more generic formatting function, which took the format as an argument.)