1 CLOCK_REALTIME 2 CLOCK_MONOTONIC 3 CLOCK_PROCESS_CPUTIME_ID 4 CLOCK_THREAD_CPUTIME_ID 5 CLOCK_MONOTONIC_RAW 6 CLOCK_REALTIME_COARSE 7 CLOCK_MONOTONIC_COARSE 8 CLOCK_BOOTTIME 9 CLOCK_REALTIME_ALARM 10 CLOCK_BOOTTIME_ALARM 11 CLOCK_SGI_CYCLE 12 CLOCK_TAI 13
