gettimeofday和clock_gettime
Charles Chan @ 2016-10-22 #Timeout #Watchdog @Program
Contents:
本文用来记录一下gettimeofday和clock_gettime的重要不同点。 参照如下的例子程序：
/*
* gcc t.c -o t -lrt
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
int main(int argc, char* argv[])
{
struct timeval now;
struct timespec tp;
struct timezone zone;
int h, m, s;
system("date +'%H:%M:%S'");
gettimeofday(&now, &zone);
h = now.tv_sec / 60 / 60 % 24;
m = now.tv_sec / 60 % 60;
s = now.tv_sec % 60;
printf("gettimeofday : %02d:%02d:%02d\n", h, m, s);
clock_gettime(CLOCK_MONOTONIC_RAW, &tp);
h = tp.tv_sec / 60 / 60 % 24;
m = tp.tv_sec / 60 % 60;
s = tp.tv_sec % 60;
printf("clock_gettime : %02d:%02d:%02d\n", h, m, s);
now.tv_sec += 60 * 10;
settimeofday(&now, &zone);
printf("\n======================\n\n");
system("date +'%H:%M:%S'");
gettimeofday(&now, &zone);
h = now.tv_sec / 60 / 60 % 24;
m = now.tv_sec / 60 % 60;
s = now.tv_sec % 60;
printf("gettimeofday : %02d:%02d:%02d\n", h, m, s);
clock_gettime(CLOCK_MONOTONIC_RAW, &tp);
h = tp.tv_sec / 60 / 60 % 24;
m = tp.tv_sec / 60 % 60;
s = tp.tv_sec % 60;
printf("clock_gettime : %02d:%02d:%02d\n", h, m, s);
return 0;
}
运行结果如下所示：
17:08:42
gettimeofday : 09:08:42
clock_gettime : 17:42:18
======================
17:08:42
gettimeofday : 09:08:42
clock_gettime : 17:42:18
可以看到，随着系统时间的改变，clock_gettime并没有受到影响。
这对于我们在代码中需要处理的各种延迟、WatchDog等会变得更加有利。