at timer - remove unused variable

at.c

// at - by Dave Cameron 2013
// A simple timer to run a job at a specific time (in the near future)
// compile like: gcc -Os at.c -o at -lrt

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <errno.h>
#include <err.h>
#include <unistd.h>

int
wait_until(time_t a)
{
	int r;
	struct timespec req;
	req.tv_sec = a;
	req.tv_nsec = 0;
	while(r = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &req, 0) && r == EINTR);
	return r;
}

int
at(int h, int m, int s)
{
	struct tm lt;
	time_t t, a;
	time(&t);
	localtime_r(&t, &lt);
	if (h>lt.tm_hour ||
	    (h==lt.tm_hour && m>lt.tm_min)) {
		// same day
		lt.tm_hour = h;
		lt.tm_min = m;
		lt.tm_sec = s;
		a = mktime(&lt);
	} else {
		// next day
		lt.tm_hour = h;
		lt.tm_min = m;
		lt.tm_sec = s;
		lt.tm_mday++;
		a = mktime(&lt);
	}
	return wait_until(a);
}

void usage(char *arg0)
{
	fprintf(stderr, "Usage: %s hh:mm[:ss] [action [args]]\n", arg0);
	fprintf(stderr, "Waits until hh:mm[:ss] today or tomorrow to do action.\n");
	exit(1);
}

int
main(int argc, char **argv)
{
	int n, h, m, s;
	if(argc<2) usage(argv[0]);
	m=0; s=0;
	n = sscanf(argv[1], "%d:%d:%d", &h,&m,&s);
	if(n<2) {
		errx(1, "invalid time");
	}
	if(argc==2) {
		return at(h,m,s);
	} else {
		if(!at(h,m,s)) {
			if(execvp(argv[2], argv + 2))
				err(1, "couldn't exec %s", argv[2]);
		}
	}
}