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#include <stdio.h>
#include <unistd.h>
#define MAX_ARGS 4
static long running = 0;
struct proc {
pid_t pid;
const char *filename;
const char *args[MAX_ARGS];
};
static struct proc spawn_table[] = {
// apple
{ 0, "bin/apple", { NULL } },
// end,
{ 0, NULL, { NULL } },
};
static int spawn(const char *filename, const char **args)
{
int ret;
// fork init
if ((ret = fork()) != 0)
return ret;
// call exec
if ((ret = exec(filename, args)))
exit(ret);
// should not happen!
exit(1);
}
static void spawn_proc(struct proc *proc)
{
int ret;
// update running on respawn
if (proc->pid)
running--;
// attempt to fork / exec
ret = spawn(proc->filename, proc->args);
// handle result
if (ret < 0) {
printf("init: cannot exec '%s': %d\n", proc->filename, ret);
proc->pid = 0;
} else {
running++;
proc->pid = ret;
}
}
static void spawn_proc_loop(struct proc *proc)
{
while (proc->pid == 0)
spawn_proc(proc);
}
static void spawn_all(void)
{
struct proc *proc;
for (proc = spawn_table; proc->filename != NULL; proc++) {
spawn_proc_loop(proc);
}
}
static struct proc *get_proc(pid_t pid)
{
struct proc *proc;
for (proc = spawn_table; proc->filename != NULL; proc++) {
if (proc->pid == pid)
return proc;
}
return NULL;
}
int main(void)
{
// spawn our processes
spawn_all();
// clean up dead on restart ours
while (1) {
struct proc *proc;
int pid, status;
// dont wait if nothing running
if (running) {
pid = waitpid(0, &status);
// ???
if (pid < 0)
continue;
} else {
spawn_all();
continue;
}
printf("init: pid %d exited with %d\n", pid, status);
// figure out if this is one of ours
proc = get_proc(pid);
if (proc == NULL)
continue;
spawn_proc_loop(proc);
}
// failed to launch anythingvery very bad!
return 1;
}
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