linux高精度struct timespec 和 struct timeval

一、struct timespec 定义：

typedef long time_t;
#ifndef _TIMESPEC
#define _TIMESPEC
struct timespec {
time_t tv_sec; // seconds 
long tv_nsec; // and nanoseconds 
};
#endif
struct timespec有两个成员，一个是秒，一个是纳秒, 所以最高精确度是纳秒。
一般由函数int clock_gettime(clockid_t, struct timespec *)获取特定时钟的时间，常用如下4种时钟：
CLOCK_REALTIME 统当前时间，从1970年1.1日算起
CLOCK_MONOTONIC 系统的启动时间，不能被设置
CLOCK_PROCESS_CPUTIME_ID 本进程运行时间
CLOCK_THREAD_CPUTIME_ID 本线程运行时间
struct tm *localtime(const time_t *clock);  //线程不安全
struct tm* localtime_r( const time_t* timer, struct tm* result );//线程安全
size_t strftime (char* ptr, size_t maxsize, const char* format,const struct tm* timeptr );

二、struct timeval 定义：

struct timeval {
time_t tv_sec; // seconds 
long tv_usec; // microseconds 
};
struct timezone{ 
int tz_minuteswest; //miniutes west of Greenwich 
int tz_dsttime; //type of DST correction 
};

struct timeval有两个成员，一个是秒，一个是微秒, 所以最高精确度是微秒。
一般由函数int gettimeofday(struct timeval *tv, struct timezone *tz)获取系统的时间 

---

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

void nowtime_ns()
{
    printf("---------------------------struct timespec---------------------------------------
"); 
    printf("[time(NULL)]     :     %ld
", time(NULL)); 
    struct timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
    printf("clock_gettime : tv_sec=%ld, tv_nsec=%ld
", ts.tv_sec, ts.tv_nsec);
    
    struct tm t;
    char date_time[64];
    strftime(date_time, sizeof(date_time), "%Y-%m-%d %H:%M:%S", localtime_r(&ts.tv_sec, &t));
    printf("clock_gettime : date_time=%s, tv_nsec=%ld
", date_time, ts.tv_nsec);
}
void nowtime_us()
{
    printf("---------------------------struct timeval----------------------------------------
"); 
    printf("[time(NULL)]    :    %ld
", time(NULL)); 
    struct timeval us;
    gettimeofday(&us,NULL);
    printf("gettimeofday: tv_sec=%ld, tv_usec=%ld
", us.tv_sec, us.tv_usec);
    
    struct tm t;
    char date_time[64];
    strftime(date_time, sizeof(date_time), "%Y-%m-%d %H:%M:%S", localtime_r(&us.tv_sec, &t));
    printf("gettimeofday: date_time=%s, tv_usec=%ld
", date_time, us.tv_usec);
}

int main(int argc, char* argv[])
{
    nowtime_ns();
    printf("
");
    nowtime_us();
    printf("
");
    return 0;
}

---

#include <time.h>

// 返回自系统开机以来的毫秒数（tick）
unsigned long GetTickCount()
{
    struct timespec ts;

    clock_gettime(CLOCK_MONOTONIC, &ts);

    return (ts.tv_sec * 1000 + ts.tv_nsec / 1000000);
}


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_MONOTONIC_RAW, &time1);
    printf("CLOCK_MONOTONIC_RAW: %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("
%d
", time(NULL));

    printf("tick count in ms: %ul
", GetTickCount());

    return 0;
}