1CLOCK_REALTIME 0
2CLOCK_MONOTONIC 1
3CLOCK_PROCESS_CPUTIME_ID 2
4CLOCK_THREAD_CPUTIME_ID 3
5CLOCK_MONOTONIC_RAW 4
6CLOCK_REALTIME_COARSE 5
7CLOCK_MONOTONIC_COARSE 6
8CLOCK_BOOTTIME 7
9CLOCK_REALTIME_ALARM 8
10CLOCK_BOOTTIME_ALARM 9
11CLOCK_SGI_CYCLE 10
12CLOCK_TAI 11
13