ubase/respawn.c

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1.7 KiB
C
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/* See LICENSE file for copyright and license details. */
#include <sys/select.h>
#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/types.h>
#include <sys/wait.h>
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#include <errno.h>
#include <fcntl.h>
#include <signal.h>
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#include <stdio.h>
#include <stdlib.h>
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#include <unistd.h>
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#include "util.h"
static void
sigterm(int sig)
{
if (sig == SIGTERM) {
kill(0, SIGTERM);
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_exit(0);
}
}
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static void
usage(void)
{
eprintf("usage: %s [-l fifo] [-d N] cmd [args...]\n", argv0);
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}
int
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main(int argc, char *argv[])
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{
char *fifo = NULL;
unsigned int delay = 0;
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pid_t pid;
char buf[BUFSIZ];
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int savederrno;
int fd;
ssize_t n;
fd_set rdfd;
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ARGBEGIN {
case 'd':
delay = estrtol(EARGF(usage()), 0);
break;
case 'l':
fifo = EARGF(usage());
break;
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default:
usage();
} ARGEND;
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if (argc < 1)
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usage();
if (fifo && delay > 0)
usage();
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setsid();
signal(SIGTERM, sigterm);
if (fifo) {
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/* TODO: we should use O_RDONLY and re-open the fd on EOF */
fd = open(fifo, O_RDWR | O_NONBLOCK);
if (fd < 0)
eprintf("open %s:", fifo);
}
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while (1) {
if (fifo) {
FD_ZERO(&rdfd);
FD_SET(fd, &rdfd);
n = select(fd + 1, &rdfd, NULL, NULL, NULL);
if (n < 0)
eprintf("select:");
if (n == 0 || FD_ISSET(fd, &rdfd) == 0)
continue;
while ((n = read(fd, buf, sizeof(buf))) > 0)
;
if (n < 0)
if (errno != EAGAIN)
eprintf("read %s:", fifo);
}
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pid = fork();
if (pid < 0)
eprintf("fork:");
switch (pid) {
case 0:
execvp(argv[0], argv);
savederrno = errno;
weprintf("execvp %s:", argv[0]);
_exit(savederrno == ENOENT ? 127 : 126);
break;
default:
waitpid(pid, NULL, 0);
break;
}
if (!fifo)
sleep(delay);
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}
/* not reachable */
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return 0;
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}