desktop-tools/iexec.c

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/*
* iexec.c: run a program and restart on file change
*
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* Copyright (c) 2017 - 2023, Přemysl Eric Janouch <p@janouch.name>
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*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted.
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*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include "config.h"
#undef PROGRAM_NAME
#define PROGRAM_NAME "iexec"
#include "liberty/liberty.c"
// This can also work on BSD if someone puts in the effort to support kqueue
#include <sys/inotify.h>
static struct
{
pid_t child; ///< Watched child or 0
bool exits; ///< Don't restart child when it exits
bool respawn; ///< Respawn child ASAP
bool killing; ///< Waiting for child to die
int inotify_fd, inotify_wd;
}
g;
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// Note that this program doesn't queue up file-based restarts
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static void
handle_inotify_event (const struct inotify_event *e, const char *base)
{
if (e->wd != g.inotify_wd || strcmp (e->name, base))
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return;
if (g.child)
{
print_debug ("file changed, killing child");
if (kill (g.child, SIGINT))
print_error ("kill: %s", strerror (errno));
g.killing = true;
}
else
{
print_debug ("file changed, respawning");
g.respawn = true;
}
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}
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static void
handle_file_change (const char *base)
{
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char buf[4096];
ssize_t len = 0;
struct inotify_event *e = NULL;
while ((len = read (g.inotify_fd, buf, sizeof buf)) > 0)
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for (char *ptr = buf; ptr < buf + len; ptr += sizeof *e + e->len)
handle_inotify_event ((e = (struct inotify_event *) buf), base);
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}
static void
spawn (char *argv[])
{
if ((g.child = fork ()) == -1)
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exit_fatal ("fork: %s", strerror (errno));
else if (g.child)
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return;
// A linker can create spurious CLOSE_WRITEs, wait until it's executable
while (1)
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{
execvp (argv[0], argv);
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print_error ("execvp: %s", strerror (errno));
sleep (1);
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}
}
static bool
check_child_death (void)
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{
int status = 0;
if (waitpid (g.child, &status, WNOHANG) != g.child)
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return true;
g.child = 0;
if (!g.killing)
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{
print_debug ("child died on its own, not respawning");
return g.exits;
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}
g.killing = false;
print_debug ("child died on request, respawning");
return g.respawn = true;
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}
static void
sigchld_handler (int signum)
{
// We need to have this handler so that pselect() can return EINTR
(void) signum;
}
int
main (int argc, char *argv[])
{
const char *target = NULL;
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static const struct opt opts[] =
{
{ 'f', "file", "PATH", 0, "watch this path rather than the program" },
{ 'e', "exits", NULL, 0, "allow the program to exit on its own" },
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{ 'd', "debug", NULL, 0, "run in debug mode" },
{ 'h', "help", NULL, 0, "display this help and exit" },
{ 'V', "version", NULL, 0, "output version information and exit" },
{ 0, NULL, NULL, 0, NULL }
};
struct opt_handler oh = opt_handler_make (argc, argv, opts,
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"PROGRAM [ARG...]", "Run a program and restart it when it changes.");
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// We have to turn that off as it causes more trouble than what it's worth
cstr_set (&oh.opt_string, xstrdup_printf ("+%s", oh.opt_string));
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int c;
while ((c = opt_handler_get (&oh)) != -1)
switch (c)
{
case 'f':
target = optarg;
break;
case 'e':
g.exits = true;
break;
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case 'd':
g_debug_mode = true;
break;
case 'h':
opt_handler_usage (&oh, stdout);
exit (EXIT_SUCCESS);
case 'V':
printf (PROGRAM_NAME " " PROGRAM_VERSION "\n");
exit (EXIT_SUCCESS);
default:
print_error ("wrong options");
opt_handler_usage (&oh, stderr);
exit (EXIT_FAILURE);
}
if (argc == optind)
{
opt_handler_usage (&oh, stderr);
exit (EXIT_FAILURE);
}
opt_handler_free (&oh);
argc -= optind;
argv += optind;
if (!target)
target = argv[0];
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(void) signal (SIGPIPE, SIG_IGN);
struct sigaction sa = { .sa_handler = sigchld_handler };
sigemptyset (&sa.sa_mask);
if (sigaction (SIGCHLD, &sa, NULL))
exit_fatal ("sigaction: %s", strerror (errno));
sigset_t chld, orig;
sigemptyset (&chld);
sigaddset (&chld, SIGCHLD);
if (sigprocmask (SIG_BLOCK, &chld, &orig))
exit_fatal ("sigprocmask: %s", strerror (errno));
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char *path = NULL;
char *dir = dirname ((path = xstrdup (target)));
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if ((g.inotify_fd = inotify_init1 (IN_NONBLOCK)) < 0)
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exit_fatal ("inotify_init1: %s", strerror (errno));
if ((g.inotify_wd = inotify_add_watch (g.inotify_fd,
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dir, IN_MOVED_TO | IN_CLOSE_WRITE)) < 0)
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exit_fatal ("inotify_add_watch: %s", strerror (errno));
free (path);
char *base = basename ((path = xstrdup (target)));
g.respawn = true;
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do
{
if (g.respawn)
{
spawn (argv);
g.respawn = false;
}
fd_set r; FD_SET (g.inotify_fd, &r);
(void) pselect (g.inotify_fd + 1, &r, NULL, NULL, NULL, &orig);
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handle_file_change (base);
}
while (check_child_death ());
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free (path);
xclose (g.inotify_fd);
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return EXIT_SUCCESS;
}