Implement fifo listener mode for respawn
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053e63968d
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0e6d7ca286
@ -2,7 +2,7 @@
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.SH NAME
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\fBrespawn\fR - Spawn the given command repeatedly
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.SH SYNOPSIS
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\fBrespawn\fR [\fB-d\fI N\fR] \fIcmd\fR [\fIargs...\fR]
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\fBrespawn\fR [\fB-l\fI fifo\fR] [\fB-d\fI N\fR] \fIcmd\fR [\fIargs...\fR]
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.SH DESCRIPTION
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\fBrespawn\fR spawns the given \fIcmd\fR in a new session
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repeatedly.
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@ -10,3 +10,9 @@ repeatedly.
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.TP
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\fB-d\fR
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Set the delay between invocations of \fIcmd\fR. It defaults to 0.
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.TP
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\fB-l\fR
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Listen on the specified \fIfifo\fR for writes. For each write
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spawn a new instance of \fIcmd\fR. This can be used in conjunction
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with a process supervisor to restart a particular program. The \fB-l\fR
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and \fB-d\fR options are incompatible. All writes are discarded.
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45
respawn.c
45
respawn.c
@ -1,6 +1,11 @@
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/* See LICENSE file for copyright and license details. */
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#include <fcntl.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/select.h>
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#include <sys/time.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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@ -9,20 +14,28 @@
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static void
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usage(void)
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{
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eprintf("usage: respawn [-d N] cmd [args...]\n");
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eprintf("usage: respawn [-l fifo] [-d N] cmd [args...]\n");
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}
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int
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main(int argc, char *argv[])
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{
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pid_t pid;
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int savederrno;
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char *fifo = NULL;
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unsigned int delay = 0;
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pid_t pid;
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char buf[BUFSIZ];
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int savederrno;
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int fd;
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ssize_t n;
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fd_set rdfd;
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ARGBEGIN {
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case 'd':
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delay = estrtol(EARGF(usage()), 0);
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break;
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case 'l':
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fifo = EARGF(usage());
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break;
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default:
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usage();
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} ARGEND;
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@ -30,7 +43,30 @@ main(int argc, char *argv[])
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if(argc < 1)
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usage();
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if (fifo && delay > 0)
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usage();
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if (fifo) {
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fd = open(fifo, O_RDWR | O_NONBLOCK);
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if (fd < 0)
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eprintf("open %s:", fifo);
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}
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while (1) {
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if (fifo) {
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FD_ZERO(&rdfd);
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FD_SET(fd, &rdfd);
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n = select(fd + 1, &rdfd, NULL, NULL, NULL);
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if (n < 0)
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eprintf("select:");
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if (n == 0 || FD_ISSET(fd, &rdfd) == 0)
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continue;
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while ((n = read(fd, buf, sizeof(buf))) > 0)
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;
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if (n < 0)
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if (errno != EAGAIN)
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eprintf("read %s:", fifo);
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}
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pid = fork();
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if (pid < 0)
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eprintf("fork:");
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@ -47,7 +83,8 @@ main(int argc, char *argv[])
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waitpid(pid, NULL, 0);
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break;
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}
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sleep(delay);
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if (!fifo)
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sleep(delay);
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}
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/* not reachable */
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return EXIT_SUCCESS;
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