Linux C 时间函数clock_gettime()的使用

函数： int clock_gettime(clockid_t clk_id, struct timespec *tp);

clockid_t： 用于指定计时时钟的类型，有以下几种类型：
CLOCK_REALTIME： 系统实时时间，从Epoch计时，可被设置更改。
CLOCK_MONOTONIC： 系统运行时间，从系统启动时开始计时，系统休眠时不再计时（NTP与硬件时钟有问题时会影响其频率，没有验证过）。
CLOCK_PROCESS_CPUTIME_ID： 本进程启动到此刻使用CPU的时间，当使用sleep等函数时不再计时。
CLOCK_THREAD_CPUTIME_ID： 本线程启动到此刻使用CPU的时间，当使用sleep等函数时不再计时。
CLOCK_MONOTONIC_RAW ： 系统运行时间，从系统启动时开始计时，系统休眠时不再计时（NTP与硬件时钟有问题时不会影响其频率，没有验证过）。
CLOCK_REALTIME_COARSE： 系统实时时间，从Epoch计时，可被设置更改，速度更快精度更低。
CLOCK_MONOTONIC_COARSE： 系统运行时间，从系统启动时开始计时，速度更快精度更低，系统休眠时不再计时（NTP与硬件时钟有问题时会影响其频率，没有验证过）。
CLOCK_BOOTTIME： 与CLOCK_MONOTONIC类似
CLOCK_REALTIME_ALARM ： 闹钟时间（应该休眠后继续计时，没验证过），系统实时时间，从Epoch计时，可被设置更改。
CLOCK_BOOTTIME_ALARM： 闹钟时间（应该休眠后继续计时，没验证过），系统运行时间，从系统启动时开始计时。
CLOCK_TAI： 原子钟的时间，与CLOCK_REALTIME类似，不可被更改，没有闰秒。

struct timespec：
struct timespec
{
time_t tv_sec; //秒
long tv_nsec; //纳秒
};

---

例子：

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <assert.h>
#include <unistd.h>

static void clock_gettime_test()
{
	struct timespec ts;

	clock_gettime(CLOCK_REALTIME, &ts);
    printf("CLOCK_REALTIME(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_REALTIME, &ts);
    printf("CLOCK_REALTIME(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);

	clock_gettime(CLOCK_MONOTONIC, &ts);
    printf("CLOCK_MONOTONIC(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_MONOTONIC, &ts);
    printf("CLOCK_MONOTONIC(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);

    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts);
    printf("CLOCK_PROCESS_CPUTIME_ID(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts);
    printf("CLOCK_PROCESS_CPUTIME_ID(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    
	clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
    printf("CLOCK_THREAD_CPUTIME_ID(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
    printf("CLOCK_THREAD_CPUTIME_ID(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);

	clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
    printf("CLOCK_MONOTONIC_RAW(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
    printf("CLOCK_MONOTONIC_RAW(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    
	clock_gettime(CLOCK_REALTIME_COARSE, &ts);
    printf("CLOCK_REALTIME_COARSE(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
    clock_gettime(CLOCK_REALTIME_COARSE, &ts);
    printf("CLOCK_REALTIME_COARSE(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    
    clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
    printf("CLOCK_MONOTONIC_COARSE(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
    clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
    printf("CLOCK_MONOTONIC_COARSE(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    
	clock_gettime(CLOCK_BOOTTIME, &ts);
    printf("CLOCK_BOOTTIME(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_BOOTTIME, &ts);
    printf("CLOCK_BOOTTIME(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);

    clock_gettime(CLOCK_REALTIME_ALARM, &ts);
    printf("CLOCK_REALTIME_ALARM(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_REALTIME_ALARM, &ts);
    printf("CLOCK_REALTIME_ALARM(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    
    clock_gettime(CLOCK_BOOTTIME_ALARM, &ts);
    printf("CLOCK_BOOTTIME_ALARM(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_BOOTTIME_ALARM, &ts);
    printf("CLOCK_BOOTTIME_ALARM(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);

    clock_gettime(CLOCK_TAI, &ts);
    printf("CLOCK_TAI(1) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);
    usleep(1000 * 1000);
	clock_gettime(CLOCK_TAI, &ts);
    printf("CLOCK_TAI(2) sec = %lu, nsec = %ld\n", ts.tv_sec, ts.tv_nsec);   
}

int main()
{
	clock_gettime_test();
	
	return 0;
}