/*
 * RUNMAINT.C - run and maintain N processes, Matthew Dillon
 *
 * example: runmaint 10 /usr/lib/sendmail -q
 */

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/wait.h>

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <fcntl.h>
#include <unistd.h>

int
main(int ac, char **av)
{
    int n;
    int s = 10;
    int i = -1;
    int r = 0;
    int ttl = 0;
    int *pids;
    char *ptr;

    if (ac < 3) {
	printf("runmaint N[:S[:I]] progname progargs...\n");
	printf("    N - max number of processes\n");
	printf("    S - new process every S seconds (after stabilized)\n");
	printf("    I - new process every I seconds (initial startup)\n");
	exit(1);
    }
    n = strtol(av[1], &ptr, 0);
    if (*ptr == ':') {
	s = strtol(ptr + 1, &ptr, 0);
	if (*ptr == ':') {
	    i = strtol(ptr + 1, &ptr, 0);
	}
    }
    if (i < 0)
	i = s * 2;

    pids = calloc(sizeof(int), n);

    if (fork() > 0)
	exit(0);

    {
	int fd;

	close(0);
	close(1);
	close(2);

	if ((fd = open("/dev/tty", O_RDWR)) >= 0) {
	    ioctl(fd, TIOCNOTTY, 0);
	    close(fd);
	}
#ifdef sgi
	setpgrp();
#else
	setpgrp(0, 0);
#endif
    }

    for (;;) {
	if (r < n) {
	    int pid;
	    if ((pid = fork()) == 0) {
		execv(av[2], av + 2);
		exit(0);
	    }
	    if (pid > 0) {
		pids[r++] = pid;
		++ttl;
	    }
	}
	{
	    int pid;
	    while ((pid = wait3(NULL, WNOHANG, NULL)) > 0) {
		int i;

		for (i = 0; i < r; ++i) {
		    if (pids[i] == pid) {
			pids[i] = pids[--r];
			break;
		    }
		}
	    }
	}
	if (ttl < n)	/* initial starts */
	    sleep(i);
	else		/* after stabilized */
	    sleep(s);
    }
    return(0);
}