嵌入式Linux 设置时间和日期 API ，它是busybox要提取的源代码。

Linux设置时间和日期的步骤：

1. 设置系统时间和日期；

2. 该系统的时间和日期，同步到硬件。

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              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); }