Programming

/usr/local/bin> gcc get_epoch_secs.c -o get_epoch_secs

return 0;

/*
Listing 6 get_date_from_secs.c
get_date_from_secs.c
pass the number of seconds since
the Epoch, and return a Gregorian
date argument
use "%02d" date format.

*/
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <errno.h>

int main(int argc, char **argv)
{
	struct tm *rettm;  /* use a pointer */
	time_t now=time(NULL);  /* add a value to now */
	char timebuf[128]={0x0}; /* place to park date time values */

	/* grab the first argument, time in seconds Note:  will segfault the old way*/
	if(argc < 2)   /* argc has to be > 1 */
	{ /* error */
		fprintf(stderr, "bad arguments -1\n"); /* you can also user perror() here */
		exit(1);
	}
	/* zero is a valid number and is valid for epoch seconds */
	errno=0;  /* set errno to a known state */
	if((now=atol(argv[1])) == 0 && errno !=0) /* atol never returns a NULL use argv */
	{ /* error */
	  /* you get to add errno checking here */
		fprintf(stderr,"invalid conversion -2\n"); /* you can also user perror() here */
		exit(1);
	}
	rettm=localtime(&now);  /* you can check for a NULL return here if you want */
	/* check your man page - some implementations only allow struct tm > Dec 13 20:45:52 UTC 1901. */
	/* use std library for time/date  use strftime */

	printf("%02d%02d%02d%02d\n", rettm->tm_mon+1, rettm->tm_mday, rettm->tm_hour, rettm->tm_min);
	strftime(timebuf, sizeof(timebuf),"%m %d %H %M %S", rettm);
	printf("%s\n", timebuf);

    return 0;
}