is clock_gettime() best for elapsed time?

[douglaskbell]

What is the best way to track elapsed real-time,
for the most kinds of Linux systems?

clock_gettime() looks great,
but I get this build error:

undefined reference to `clock_gettime'

..even though I have #include "time.h"

Here is my uber-goal:



// Returns fractional seconds that have elapsed since Start_Ticks was set.
float elapsed_seconds( unsigned Start_Ticks )
{
struct timespec tp;
clock_gettime( CLOCK_REALTIME, &tp );
return ( tp.tv_nsec - Start_Ticks ) / (double)1000000;
}

[Rubberman]

That is a linker error, not a compile error. Show how you are building your program, and tell us which source file has the implementation of elapsed_seconds() and which main().