cmd-timer

timer.c (3592B)

// SPDX-FileCopyrightText: 2025 Haelwenn (lanodan) Monnier <contact+cmd-timer@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _POSIX_C_SOURCE 200809L
#include "strtodur.h"
#include <errno.h>
#include <limits.h> // UINT_MAX
#include <signal.h> // sigaction
#include <spawn.h>  // posix_spawnp
#include <stdbool.h>
#include <stdio.h>    // fprintf, fputs
#include <stdlib.h>   // exit
#include <string.h>   // strerror
#include <sys/wait.h> // waitpid
#include <time.h>     // timer_create
#include <unistd.h>   // sleep, getopt
extern char **environ;
static char **args;
const char *argv0 = "timer";
static void
sig_timer(int sig)
{
	pid_t child = -1;
	errno = 0;
	int ret = posix_spawnp(&child, args[0], NULL, NULL, args, environ);
	if(ret != 0)
	{
		fprintf(stderr, "timer: error: Failed spawning command '%s': %s\n", args[0], strerror(ret));
		exit(1);
	}
}
static void
sig_chld(int sig)
{
	int chld_stat = 0;
	waitpid((pid_t)-1, &chld_stat, WNOHANG);
	if(!WIFEXITED(chld_stat)) return;
	if(WEXITSTATUS(chld_stat) != 0) exit(WEXITSTATUS(chld_stat));
}
static void
bad_usage()
{
	fputs("Usage: timer [-w] <interval> <command> [arguments...]\n", stderr);
	exit(1);
}
static void
timer_errx(int err, char *msg)
{
	fprintf(stderr, "timer: error: %s: %s\n", msg, strerror(errno));
	exit(err);
}
int
main(int argc, char *argv[])
{
	bool opt_w = false;
	for(char c = -1; (c = getopt(argc, argv, ":w")) != -1;)
	{
		switch(c)
		{
		case 'w':
			opt_w = true;
			break;
		default:
			fprintf(stderr, "timer: error: Unhandled option -%c\n", optopt);
			return 1;
		}
	}
	argc -= optind;
	argv += optind;
	if(argc < 2)
	{
		fprintf(stderr, "timer: error: Got '%d' arguments instead of at least 2\n", argc);
		bad_usage();
	}
	struct timespec dur = {
	    .tv_sec = 0,
	    .tv_nsec = 0,
	};
	if(strtodur(*argv, &dur) != 0) return 1;
	if(dur.tv_sec == 0 && dur.tv_nsec == 0)
	{
		fputs("timer: error: Got a duration of 0\n", stderr);
		return 1;
	}
	argc--;
	argv++;
	struct sigaction sa_alrm;
	sa_alrm.sa_handler = &sig_timer;
	sigemptyset(&sa_alrm.sa_mask);
	sa_alrm.sa_flags = SA_RESTART;
	if(sigaction(SIGALRM, &sa_alrm, NULL) != 0)
	{
		fprintf(stderr, "timer: error: Failed registering signal handler: %s\n", strerror(errno));
		return 1;
	}
	struct sigaction sa_chld;
	sa_chld.sa_handler = &sig_chld;
	sigemptyset(&sa_chld.sa_mask);
	sa_chld.sa_flags = SA_RESTART;
	if(sigaction(SIGCHLD, &sa_chld, NULL) != 0)
	{
		fprintf(stderr, "timer: error: Failed registering signal handler: %s\n", strerror(errno));
		return 1;
	}
	struct sigevent timer_se;
	timer_se.sigev_signo = SIGALRM;
	timer_se.sigev_notify = SIGEV_SIGNAL;
	timer_t timer;
	if(timer_create(0, &timer_se, &timer) != 0)
	{
		fprintf(stderr, "timer: error: Failed creating timer: %s\n", strerror(errno));
		return 1;
	}
	struct itimerspec timerspec = {
	    .it_value = dur,
	    .it_interval = dur,
	};
	if(timer_settime(timer, 0, &timerspec, NULL) != 0)
	{
		fprintf(stderr, "timer: error: Failed setting timer: %s\n", strerror(errno));
		return 1;
	}
	args = argv;
	sigset_t sigmask;
	sigfillset(&sigmask);
	if(sigdelset(&sigmask, SIGALRM) != 0)
		timer_errx(1, "Failed adding SIGALRM to sigsuspend sigmask");
	if(sigdelset(&sigmask, SIGCHLD) != 0)
		timer_errx(1, "Failed adding SIGCHLD to sigsuspend sigmask");
	if(sigdelset(&sigmask, SIGINT) != 0) timer_errx(1, "Failed adding SIGINT to sigsuspend sigmask");
	if(sigdelset(&sigmask, SIGTERM) != 0)
		timer_errx(1, "Failed adding SIGTERM to sigsuspend sigmask");
	if(!opt_w) sig_timer(0);
	while(sigsuspend(&sigmask))
		;
	return 0;
}