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