1#value_indexed
2CLOCK_REALTIME 0
3CLOCK_MONOTONIC 1
4CLOCK_PROCESS_CPUTIME_ID 2
5CLOCK_THREAD_CPUTIME_ID 3
6CLOCK_MONOTONIC_RAW 4
7CLOCK_REALTIME_COARSE 5
8CLOCK_MONOTONIC_COARSE 6
9CLOCK_BOOTTIME 7
10CLOCK_REALTIME_ALARM 8
11CLOCK_BOOTTIME_ALARM 9
12CLOCK_SGI_CYCLE 10
13CLOCK_TAI 11
14