使用C库功能设置系统时间

Question

我可以使用struct tm和time（），localtime（），asctime（）来获取系统时间。但是我需要有关如何使用c程序设置系统时间的帮助。

Answer 1

if you don't want to execute a shell command you can (as you mentioned) use the settimeofday, i would start by reading the MAN page , or looking for some examples

here's an example:

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

int main(int argc, char *argv[])
{
    struct timeval now;
    int rc;

    now.tv_sec=866208142;
    now.tv_usec=290944;

    rc=settimeofday(&now, NULL);
    if(rc==0) {
        printf("settimeofday() successful.\n");
    }
    else {
        printf("settimeofday() failed, "
        "errno = %d\n",errno);
        return -1;
    }

    return 0;
}

Shamelessly ripped From IBMs documentation , the struct timeval struct holds the number of seconds (as a long ) plus the number of microseconds (as a long ) from 1 January 1970, 00:00:00 UTC (Unix Epoch time). So you will need to calculate these numbers in order to set the time. you can use these helper functions , to better handle dealing with the timeval struct.