Linux 设置系统时间和日期 API

#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <time.h>
#include <linux/rtc.h>
#include <linux/capability.h>

int  SetSysDateAndTime(const char *time_str);
void SetHWClockFromSysClock(int utc);

static int  rtc_xopen(const char **default_rtc, int flags);
static void write_rtc(time_t t, int utc);

static const char *rtcname;

int main(void)
{
const char time_str[] = "1989-11-22 11:22:33";
SetSysDateAndTime(time_str);
SetHWClockFromSysClock(0);

system("reboot");

return 0;
}

int SetSysDateAndTime(const char *time_str)
{
struct tm 			time_tm;
struct timeval 	time_tv;
time_t 					timep;
int 						ret;

if(time_str == NULL)
{
fprintf(stderr, "time string args invalid!\n");
return -1;
}

sscanf(time_str, "%d-%d-%d %d:%d:%d", &time_tm.tm_year, &time_tm.tm_mon, &time_tm.tm_mday, &time_tm.tm_hour, &time_tm.tm_min, &time_tm.tm_sec);
time_tm.tm_year 	-= 1900;
time_tm.tm_mon 		-= 1;
time_tm.tm_wday 	= 0;
time_tm.tm_yday 	= 0;
time_tm.tm_isdst	= 0;

timep = mktime(&time_tm);
time_tv.tv_sec  = timep;
time_tv.tv_usec = 0;

ret = settimeofday(&time_tv, NULL);
if(ret != 0)
{
fprintf(stderr, "settimeofday failed\n");
return -2;
}

return 0;
}

void SetHWClockFromSysClock(int utc)
{
struct timeval tv;

gettimeofday(&tv, NULL);
//if (gettimeofday(&tv, NULL))
//	bb_perror_msg_and_die("gettimeofday() failed");
write_rtc(tv.tv_sec, utc);
}

static int  rtc_xopen(const char **default_rtc, int flags)
{
int rtc;

if (!*default_rtc) {
*default_rtc = "/dev/rtc";
rtc = open(*default_rtc, flags);
if (rtc >= 0)
return rtc;
*default_rtc = "/dev/rtc0";
rtc = open(*default_rtc, flags);
if (rtc >= 0)
return rtc;
*default_rtc = "/dev/misc/rtc";
}

return open(*default_rtc, flags);
}

static void write_rtc(time_t t, int utc)
{
#define RTC_SET_TIME	_IOW('p', 0x0a, struct rtc_time) /* Set RTC time    */

struct tm tm;
int rtc = rtc_xopen(&rtcname, O_WRONLY);

tm = *(utc ?

gmtime(&t) : localtime(&t));
tm.tm_isdst = 0;

ioctl(rtc, RTC_SET_TIME, &tm);

close(rtc);
}