linux – 你如何在shell中获得clock_gettime(2)时钟？

在shell中你可以使用日期工具：

date +%s.%N
date +%s%N
nanoseconds_since_70=$(date +%s%N)

从男人约会：

%s     seconds since 1970-01-01 00:00:00 UTC
       %N     nanoseconds (000000000..999999999)

纳秒部分以正确的方式补充秒：当％N从999999999变为0时,％s增加一秒.我没有参考(请编辑,如果你能找到它),但只是工作.

date utility x clock_gettime

请注意,该数字不受时区更改的影响,但会受系统时钟更改的影响,例如系统管理员,NTP和调用功能所做的更改.但是,除了管理员更改外,clock_gettime函数中的CLOCK_MONOTONIC也会受到影响.

CLOCK_MONOTONIC -- Clock  that  cannot  be set and represents monotonic time
 since some unspecified starting point.  This clock is not affected by 
 discontinuous jumps in the system time (e.g.,if the system administrator 
 manually changes the clock),but is affected by the incremental adjustments
 performed by adjtime(3) and NTP.

较新的系统有更好的解决方案：CLOCK_MONOTIC_RAW.尽管如此,这是一个shell解决方案.

了解更多

Monotonic function in Wikipedia

@caf用户回答Difference between CLOCK_REALTIME and CLOCK_MONOTONIC?：

CLOCK_MONOTONIC represents the absolute elapsed wall-clock time since some
arbitrary,fixed point in the past. It isn't affected by changes in the 
system time-of-day clock. 

If you want to compute the elapsed time between two events observed on the one
machine without an intervening reboot,CLOCK_MONOTONIC is the best option.