I would like to get the current timestamp and print it out using fprintf.
An important point is to consider if you perform tasks based on difference between 2 timestamps because you will get odd behavior if you generate it with gettimeofday(), and even clock_gettime(CLOCK_REALTIME,..) at the moment where you will set the time of your system.
To prevent such problem, use clock_gettime(CLOCK_MONOTONIC_RAW, &tms) instead.