respawn - a small utility to respawn process that exists when should keep up.

Makefile

CFLAGS_respawn += -Wall
respawn: respawn.c
	$(CC) $(CFLAGS_$@) $(LDFLAGS_$@) $(CFLAGS) $(LDFLAGS) -o $@ $<

clean:
	rm -f respawn

respawn.c

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/wait.h>

#define log(fmt, args...) syslog(LOG_MAKEPRI(LOG_USER, LOG_INFO), fmt, ##args)

int main(int argc, char **argv)
{
	openlog("respawn", LOG_PERROR, 0);
	int rc = daemon(0, 0);
	if (rc) {
		log("daemon failed %d/%s", errno, strerror(errno));
		closelog();
		return -1;
	}

	while (1) {
		log("Starting %s", argv[1]);
		pid_t pid = fork();
		if (pid == 0) { /* child */
			return execvp(argv[1], &argv[1]);
		} else if (pid > 0) { /* parent */
			int chldstatus;
			pid_t chldpid = waitpid(pid, &chldstatus, 0);
			if (chldpid == pid) { /* waitpid success */
				if (WIFEXITED(chldstatus)) {
					log("%s exited, respawing", argv[1]);
					log("%s status: %d", argv[1], chldstatus);
				}
				continue;
			}
		} else { /* error */
			log("fork error %d/%s", errno, strerror(errno));
			return -1;
		}
	}
	closelog();
	return 0;
		
}