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	respawn.c - ubase - suckless linux base utils
	git clone git://git.suckless.org/ubase
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	respawn.c (1914B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include <sys/stat.h>
	3 #include <sys/time.h>
	4 #include <sys/types.h>
	5 #include <sys/wait.h>
	6
	7 #include <errno.h>
	8 #include <fcntl.h>
	9 #include <poll.h>
	10 #include <signal.h>
	11 #include <stdio.h>
	12 #include <stdlib.h>
	13 #include <unistd.h>
	14
	15 #include "util.h"
	16
	17 static void
	18 sigterm(int sig)
	19 {
	20 if (sig == SIGTERM) {
	21 kill(0, SIGTERM);
	22 _exit(0);
	23 }
	24 }
	25
	26 static void
	27 usage(void)
	28 {
	29 eprintf("usage: %s [-l fifo] [-d N] cmd [args...]\n", argv0);
	30 }
	31
	32 int
	33 main(int argc, char *argv[])
	34 {
	35 char *fifo = NULL;
	36 unsigned int delay = 0;
	37 pid_t pid;
	38 char buf[BUFSIZ];
	39 int savederrno;
	40 ssize_t n;
	41 struct pollfd pollset[1];
	42 int polln;
	43
	44 ARGBEGIN {
	45 case 'd':
	46 delay = estrtol(EARGF(usage()), 0);
	47 break;
	48 case 'l':
	49 fifo = EARGF(usage());
	50 break;
	51 default:
	52 usage();
	53 } ARGEND;
	54
	55 if (argc < 1)
	56 usage();
	57
	58 if (fifo && delay > 0)
	59 usage();
	60
	61 setsid();
	62
	63 signal(SIGTERM, sigterm);
	64
	65 if (fifo) {
	66 pollset->fd = open(fifo, O_RDONLY \| O_NONBLOCK);
	67 if (pollset->fd < 0)
	68 eprintf("open %s:", fifo);
	69 pollset->events = POLLIN;
	70 }
	71
	72 while (1) {
	73 if (fifo) {
	74 pollset->revents = 0;
	75 polln = poll(pollset, 1, -1);
	76 if (polln <= 0) {
	77 if (polln == 0 \|\| errno == EAGAIN)
	78 continue;
	79 eprintf("poll:");
	80 }
	81 while ((n = read(pollset->fd, buf, sizeof(buf)))…
	82 ;
	83 if (n < 0)
	84 if (errno != EAGAIN)
	85 eprintf("read %s:", fifo);
	86 if (n == 0) {
	87 close(pollset->fd);
	88 pollset->fd = open(fifo, O_RDONLY \| O_NO…
	89 if (pollset->fd < 0)
	90 eprintf("open %s:", fifo);
	91 pollset->events = POLLIN;
	92 }
	93 }
	94 pid = fork();
	95 if (pid < 0)
	96 eprintf("fork:");
	97 switch (pid) {
	98 case 0:
	99 execvp(argv[0], argv);
	100 savederrno = errno;
	101 weprintf("execvp %s:", argv[0]);
	102 _exit(savederrno == ENOENT ? 127 : 126);
	103 break;
	104 default:
	105 waitpid(pid, NULL, 0);
	106 break;
	107 }
	108 if (!fifo)
	109 sleep(delay);
	110 }
	111 /* not reachable */
	112 return 0;
	113 }