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
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 usingnamespace 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 return0;
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 }
