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#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <string.h>

#define CRONOLOG "/usr/sbin/cronolog"

char *pidfile;

void die(int sig) {
	/* kill off children */
	kill(0, SIGTERM);
	/* remove pid file, quit */
	unlink(pidfile);
	exit(0);
}

struct sigaction sigdie = { .sa_handler = die };

int main(int argc, char *argv[]) {
	time_t t = 0;
	pid_t pid = 0;
	int fd, pidfd, pidlen = 16;
	char *fifo, *log, pidstr[16];

	if (argc != 4) {
		fprintf(stderr, "Usage: %s /path/to/pidfile /path/to/fifo"
				" /path/to/logs/%%Y%%m%%d.log\n", argv[0]);
		exit(1);
	}

	pidfile = argv[1];
	fifo = argv[2];
	log = argv[3];

	/* Test for fifo access, leave open for use */
	/* O_NONBLOCK allows us to fork into the background */
	fd = open(fifo, O_RDONLY|O_NONBLOCK);
	if (fd == -1) {
		fprintf(stderr, "Cannot open fifo %s: %s\n", fifo, strerror(errno));
		exit(1);
	}

	pid = fork();

	if (pid == 0) {
		/* CHILD 0 */

		/* Record pid to pidfile */
		pidfd = open(pidfile, O_WRONLY|O_CREAT|O_EXCL, 0644);
		if (pidfd == -1) {
			fprintf(stderr, "Cannot create and open pid file %s: %s\n",
			pidfile, strerror(errno));
			exit(1);
		} else {
			pidlen = snprintf(pidstr, pidlen, "%d\n", getpid());
			write(pidfd, pidstr, pidlen);
			close(pidfd);
		}

		/* close shell output */
		close(0);
		close(1);
		close(2);

		/* set a process group for easy cleanup */
		setpgrp();
		sigaction(SIGTERM, &sigdie, NULL);

		/* keep the cronolog process open */
		while (1) {
			t = time(NULL);
			pid = fork();
			if (pid == 0) {
				/* CHILD 1 */

				/* replace stdin with fifo */
				dup2(fd, 0);
				/* unset O_NONBLOCK */
				fcntl(0, F_SETFL, 0);
				/* exec cronolog */
				execl(CRONOLOG, CRONOLOG, log, (char *) 0);
				/* filure! give up on life */
				exit(1);
			} else {
				/* PARENT 1 */
				/* watch child 1 */
				waitpid(pid, NULL, 0);
				if (time(NULL) - t < 2) {
					/* restarting too fast, wait 10 seconds */
					sleep(10);
				}
			}
		}
	}

	/* PARENT 0 exits */
	close(fd);

	return 0;
}

/* vim: set ts=4 sw=4 tw=80: */