在软件设计中经常会用到关于时间的处理，用来计算语句、函数的执行时间，这时就需要精确到毫秒甚至是微妙的时间。

 

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

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

 

struct timeval {

    time_t      tv_sec;     /* seconds */

    suseconds_t tv_usec;    /* microseconds */

};

 

struct timezone {

    int tz_minuteswest;     /* minutes west of Greenwich */

    int tz_dsttime;         /* type of DST correction */

};

 

下面是个简单的例子，用来统计程序的执行时间：

       …

struct timeval t_start,t_end;

    long cost_time = 0;

 

//get start time

gettimeofday(&t_start, NULL);

printf("Start time: %ld us", t_start.tv_usec);

 

//some operation

…

 

//get end time

gettimeofday(&t_end, NULL);

printf("End time: %ld us", t_end.tv_usec);

 

//calculate time slot

cost_time = t_end.tv_usec - t_start.tv_usec;

printf("Cost time: %ld us", cost_time);

…

 

输出：

Start time: 438061 us

End time: 459867 us

Cost time: 21806 us

 

demo:

#include 
     
      #include 
      
       #include 
       
        int main(int argc, char *argv[]){printf("Hello, world!\n");struct timeval tvafter,tvpre;struct timezone tz;int sum = 0;      int i=0;gettimeofday (&tvpre , &tz);for(i = 0; i < 100000000; i++){     sum += i;}      gettimeofday (&tvafter , &tz);printf("sum=%d 花费时间:%d\n",sum, (tvafter.tv_sec-tvpre.tv_sec)*1000+(tvafter.tv_usec-tvpre.tv_usec)/1000);return EXIT_SUCCESS;}