Linux Setup system time and date API

Embedded Linux sets the time and date API, which is the source code that busybox to extract.

Steps for Linux to set the time and date:

1. Set the system time and date;

2. The system's time and date are synchronized to the hardware.

#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 (&AMP;TIME_TM);    Time_tv.tv_sec = TIMEP;    time_tv.tv_usec = 0;    ret = Settimeofday (&AMP;TIME_TV, NULL);        if (ret! = 0) {fprintf (stderr, "Settimeofday failed\n");    Return-2; }return 0;} void Sethwclockfromsysclock (int UTC) {struct Timeval tv;gettimeofday (&AMP;TV, null);//if (Gettimeofday (&AMP;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 = Ope  N (*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);}

Linux Setup system time and date API