linux clock_gettime函数详解

http://blog.csdn.net/shanglihong/article/details/6562869

 

long sys_clock_gettime (clockid_t which_clock, struct timespec *tp);

which_clock参数解释

CLOCK_REALTIME:系统实时时间,随系统实时时间改变而改变,即从UTC1970-1-1 0:0:0开始计时,中间时刻如果系统时间被用户该成其他,则对应的时间相应改变
CLOCK_MONOTONIC:从系统启动这一刻起开始计时,不受系统时间被用户改变的影响
CLOCK_PROCESS_CPUTIME_ID:本进程到当前代码系统CPU花费的时间
CLOCK_THREAD_CPUTIME_ID:本线程到当前代码系统CPU花费的时间

结构体的结构：

struct timespec {
       time_t tv_sec; /* seconds */
       long tv_nsec; /* nanoseconds */
};

//test9.c

#include <stdio.h>
#include <time.h>

int main()
{
struct timespec time1 = {0, 0};
clock_gettime(CLOCK_REALTIME, &time1);
printf("CLOCK_REALTIME: %d, %d", time1.tv_sec, time1.tv_nsec);
clock_gettime(CLOCK_MONOTONIC, &time1);
printf("CLOCK_MONOTONIC: %d, %d", time1.tv_sec, time1.tv_nsec);
clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);
printf("CLOCK_PROCESS_CPUTIME_ID: %d, %d", time1.tv_sec, time1.tv_nsec);
clock_gettime(CLOCK_THREAD_CPUTIME_ID, &time1);
printf("CLOCK_THREAD_CPUTIME_ID: %d, %d", time1.tv_sec, time1.tv_nsec);

printf("/n%d/n", time(NULL));
sleep(1);
}

如果无法编译,默认没有加入该库,请用gcc test9.c -lrt运行

在引入的librt.so 的路径：{/usr/lib/x86_64-linux-gnu}

测试 #time ./a.out

 

http://www.cnblogs.com/daqiwancheng/archive/2010/07/01/1769522.html

Linux下使用clock_gettime给程序计时

  哦，clock_gettime( ) 提供了纳秒的精确度，给程序计时可是不错哦；

 

函数的原型如下：

int clock_gettime(clockid_t clk_id, struct timespect * tp);

clockid_t clk_id用于指定计时时钟的类型，对于我们Programmr以下三种比较常用：

CLOCK_REALTIME, a system-wide realtime clock.

CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.

CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.

CLOCK_REALTIME, a system-wide realtime clock.

CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.

CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.

struct timespect *tp用来存储当前的时间，其结构如下：

1 struct timespec {
2 time_t tv_sec; /* seconds */
3 long tv_nsec; /* nanoseconds */
4 };

呵呵，好啦！该讲的都刚清楚了，下面我们就上代码把；

代码

1 #include < iostream >
2 #include < time.h >
3   using namespace std;
4
5 timespec diff(timespec start, timespec end);
6
7   int main()
8 {
9 timespec time1, time2;
10 int temp;
11 clock_gettime(CLOCK_PROCESS_CPUTIME_ID, & time1);
12 for ( int i = 0 ; i < 242000000 ; i ++ )
13 temp += temp;
14 clock_gettime(CLOCK_PROCESS_CPUTIME_ID, & time2);
15 cout << diff(time1,time2).tv_sec << " : " << diff(time1,time2).tv_nsec << endl;
16 return 0 ;
17 }
18
19 timespec diff(timespec start, timespec end)
20 {
21 timespec temp;
22 if ((end.tv_nsec - start.tv_nsec) < 0 ) {
23 temp.tv_sec = end.tv_sec - start.tv_sec - 1 ;
24 temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
25 } else {
26 temp.tv_sec = end.tv_sec - start.tv_sec;
27 temp.tv_nsec = end.tv_nsec - start.tv_nsec;
28 }
29 return temp;
30 }