c - clock_gettime系统调用的clk_id有什么区别

Question

我试图打发时间:

int clock_gettime(clockid_t clk_id, struct timespec *tp)

我对应该输入什么 clk_id 感到困惑。有:

CLOCK_REALTIME
CLOCK_REALTIME_COARSE
CLOCK_MONOTONIC
CLOCK_MONOTONIC_COARSE
CLOCK_MONOTONIC_RAW
CLOCK_BOOTTIME
CLOCK_PROCESS_CPUTIME_ID
CLOCK_THREAD_CPUTIME_ID

它们有什么区别？

Answer 1

这里是一些总结，查看手册页 man clock_gettime

 CLOCK_REALTIME   identifies the realtime clock for the system.  

 CLOCK_MONOTONIC  identifies a clock that increases at a steady rate
                  (monotonically). 

 CLOCK_BOOTTIME   identical to CLOCK_MONOTONIC, except it also includes 
                  any time that the system is suspended.

 CLOCK_PROCESS_CPUTIME_ID
                  identifies a per process clock based on tick values.

 CLOCK_THREAD_CPUTIME_ID
                  identifies a per thread clock based on tick values.