linux系统时间编程(5) UTC秒数转日历时间gmtime函数，日历时间转字符串asctime函数

UTC秒数转日历时间—gmtime函数

<time.h>
struct tm *gmtime ( const time_t *timer );	(1)
struct tm *gmtime_r( const time_t *timer, struct tm *buf );	(2)	(since C23)
struct tm