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/* vi: set sw=4 ts=4:
*
* oneit.c, tiny one-process init replacement.
*
* Copyright 2005, 2007 by Rob Landley <rob@landley.net>.
*
* Not in SUSv3.
USE_ONEIT(NEWTOY(oneit, "+<1c:p", TOYFLAG_SBIN))
config ONEIT
bool "oneit"
default y
help
usage: oneit [-p] [-c /dev/tty0] command [...]
A simple init program that runs a single supplied command line with a
controlling tty (so CTRL-C can kill it).
-p Power off instead of rebooting when command exits.
-c Which console device to use.
The oneit command runs the supplied command line as a child process
(because PID 1 has signals blocked), attached to /dev/tty0, in its
own session. Then oneit reaps zombies until the child exits, at
which point it reboots (or with -p, powers off) the system.
*/
#include "toys.h"
#include <sys/reboot.h>
// The minimum amount of work necessary to get ctrl-c and such to work is:
//
// - Fork a child (PID 1 is special: can't exit, has various signals blocked).
// - Do a setsid() (so we have our own session).
// - In the child, attach stdio to /dev/tty0 (/dev/console is special)
// - Exec the rest of the command line.
//
// PID 1 then reaps zombies until the child process it spawned exits, at which
// point it calls sync() and reboot(). I could stick a kill -1 in there.
#define TT toy.oneit
void oneit_main(void)
{
int i;
pid_t pid;
// Create a new child process.
pid = vfork();
if (pid) {
// pid 1 just reaps zombies until it gets its child, then halts the system.
while (pid!=wait(&i));
sync();
reboot(toys.optflags ? RB_POWER_OFF : RB_AUTOBOOT);
}
// Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
setsid();
for (i=0; i<3; i++) {
close(i);
xopen(TT.console ? TT.console : "/dev/tty0",O_RDWR);
}
// Can't xexec() here, because we vforked so we don't want to error_exit().
toy_exec(toys.optargs);
execvp(*toys.optargs, toys.optargs);
_exit(127);
}
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