clock_getres() returns the resolution of clock clock_id in res if res != NULL clock_getres() supports a clock_id of CLOCK_REALTIME clock_getres() supports a clock_id of CLOCK_MONOTONIC (if pt:MON) clock_getres() returns 0 on success clock_getres returns -1 on failure clock_getres() sets errno=EINVAL if clock_id does not refer to a known clock CPT If _POSIX_CPUTIME is defined, implementations shall support clock ID values obtained by invoking clock_getcpuclockid( ), which represent the CPU-time clock of a given process. Implementations shall also support the special clockid_t value CLOCK_PROCESS_CPUTIME_ID, which represents the CPU-time clock of the calling process when invoking one of the clock_*( ) or timer_*( ) functions. For these clock IDs, the values returned by clock_gettime( ) and specified by clock_settime( ) represent the amount of execution time of the process associated with the clock. If _POSIX_THREAD_CPUTIME is defined, implementations shall support clock ID values obtained by invoking pthread_getcpuclockid( ), which represent the CPU-time clock of a given thread. Implementations shall also support the special clockid_t value CLOCK_THREAD_CPUTIME_ID, which represents the CPU-time clock of the calling thread when invoking one of the clock_*( ) or timer_*( ) functions. For these clock IDs, the values returned by clock_gettime( ) and specified by clock_settime( ) shall represent the amount of execution time of the thread associated with the clock.