Linux 获取微秒级时间的函数 gettimeofday

1. 简介

一言以蔽之，返回本时区从 19700101 的 00:00开始，到本函数执行时的秒数和微秒数。

1970年到目前大约是54+年的时间。

声明：

 #include

       int gettimeofday(struct timeval *tv, struct timezone *tz);

       int settimeofday(const struct timeval *tv, const struct timezone *tz);

描述：

DESCRIPTION
       The functions gettimeofday() and settimeofday() can get and set the time as well as a timezone.

       The tv argument is a struct timeval (as specified in ):

           struct timeval {
               time_t      tv_sec;     /* seconds */
               suseconds_t tv_usec;    /* microseconds */
           };

       and gives the number of seconds and microseconds since the Epoch (see time(2)).

       The tz argument is a struct timezone:

           struct timezone {
               int tz_minuteswest;     /* minutes west of Greenwich */
               int tz_dsttime;         /* type of DST correction */
           };

 RETURN VALUE
       gettimeofday() and settimeofday() return 0 for success, or -1 for failure (in which case errno is set appropriately).

跟多内容：

$ man gettimeofday

2. 应用示例

这个示例将时间换算为了秒，也可以换算为微妙；

可以执行两次本函数，获得 time1 和 time2，获得两者之间经历的时间长度。

hello_get_time_of_day.cpp

#include 
#include 


extern "C"
double get_seconds_from_19700101_time( void )
{
    struct timeval t;
    gettimeofday( &t, NULL );
    return t.tv_sec + t.tv_usec*1e-6;
}


int main()
{
        double x = 0.0;

        x = get_seconds_from_19700101_time();

        printf("\nx = %13.2f seconds\n  = %13.2f days\n  = %13.2f years\n\n", x, x/60.0/60.0/24.0, x/60.0/60.0/24.0/365.0);

        return 0;
}

Makefile:

hello_get_time_of_day:

.PHONY: clean
clean:
        -rm -rf hello_get_time_of_day

3. 运行效果