Linux-C语言中gettimeofday()函数的使用方法（转载）

1.简介：

在C语言中可以使用函数gettimeofday()函数来得到时间。它的精度可以达到微妙

2.函数原型：

#include<sys/time.h>

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

3.说明：

gettimeofday()会把目前的时间用tv 结构体返回，当地时区的信息则放到tz所指的结构中

4.结构体：

1>timeval

struct timeval{

long tv_sec;/*秒*/

long tv_usec;/*微妙*/

}；

2>timezone 结构定义为：

struct timezone{

int tz_minuteswest;/*和greenwich 时间差了多少分钟*/

int tz_dsttime;/*type of DST correction*/

}

3>在gettimeofday()函数中tv或者tz都可以为空。如果为空则就不返回其对应的结构体。

4>函数执行成功后返回0，失败后返回-1，错误代码存于errno中。

5.程序实例：

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

#include<unistd.h>

int main()

{

struct timeval tv;

struct timezone tz;

gettimeofday(&tv,&tz);

printf(“tv_sec:%d\n”,tv.tv_sec);

printf(“tv_usec:%d\n”,tv.tv_usec);

printf(“tz_minuteswest:%d\n”,tz.tz_minuteswest);

printf(“tz_dsttime:%d\n”,tz.tz_dsttime);

}

说明：在使用gettimeofday()函数时，第二个参数一般都为空，因为我们一般都只是为了获得当前时间，而不用获得timezone的数值

gettimeofday()

Get the current time

Synopsis:

#include <sys/time.h>

int gettimeofday( struct timeval * when,
void * not_used );

Arguments:

whenA pointer to a timeval structure where the function can store the time. The struct timeval contains the following members:

time_t tv_sec — the number of seconds since the start of the Unix Epoch.

suseconds_t tv_usec — the number of microseconds.

not_usedThis pointer must be NULL or the behavior of gettimeofday() is unspecified. This argument is provided only for backwards compatibility.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The gettimeofday() function returns the current time in when in seconds and microseconds, since the Unix Epoch, 00:00:00 January 1, 1970 Coordinated Universal Time (UTC) (formerly known as Greenwich Mean Time (GMT)).

Returns:

0 for success, or -1 if an error occurs (errno is set).

Errors:

EFAULT An error occurred while accessing the when buffer.