timeval

  DESCRIPTION 
  The functions gettimeofday and settimeofday can get and set the time as 
  well as a timezone. The tv argument is a timeval struct, as specified in <sys/time.h>: 
       struct timeval { 
        time_t tv_sec; /* seconds */ 
        suseconds_t tv_usec; /* microseconds */ 
  }; 
        其中返回的timeval值为Epoch(00:00:00 1970-01-01 UTC)到创建struct timeval时的时间,tv_sec为秒数部分,tv_usec为微秒数部分(10的-6次方秒)。比如当前程序运行的tv_sec为1244770435,tv_usec为442388,即当前时间距Epoch时间1244770435秒,442388微秒。

测试代码如下: 
  #include <stdio.h> 
  #include <sys/time.h> 
  #include <time.h> 
  int gettimeofday(struct timeval *tv, struct timezone *tz); 
  int main(int argc,char * argv[]){ 
        struct timeval tv; 
        while(1){ 
              gettimeofday(&tv,NULL); 
                   printf(“time %u:%u/n”,tv.tv_sec,tv.tv_usec); 
             sleep(2); 
        } 
     return 0; 
   }

运行结果如下:
time 1259471701:970193
time 1259471703:971529
time 1259471705:973225
time 1259471707:974921

timespec
/* POSIX.1b structure for a time value. This is like a `struct timeval’ but
   has nanoseconds instead of microseconds. */
struct timespec
{
    __time_t tv_sec;        /* Seconds. */
    long int tv_nsec;       /* Nanoseconds. */
};

 

与struct timeval 不同,将结构体内成员微秒变换成纳秒

struct timeval 和 struct timespec
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