#include <errno.h> /* errno */
#include <stdio.h> /* fprintf(3), stderr */
#include <stdlib.h> /* strtol(3) */
#include <sysexits.h> /* EX_USAGE */
#include <unistd.h> /* sleep(3) */

static char *program_name = "sleep";

int main(int argc, char **argv){
	int s;
	extern int errno;

	if(argc != 2){
usage:		fprintf(stderr, "Usage: %s [seconds]\n",
				argv[0] == NULL ? program_name : argv[0]);
		return EX_USAGE;
	}
	errno = 0;
	s = strtol(argv[1], &argv[1], 10);
	if(*argv[1] != '\0' || errno != 0)
		goto usage;
	while(s > 0)
		s = sleep(s);
	return s;
}