annotate toys/oneit.c @ 194:30a6db5a95c2

Add comments about SUSv3 specs (or lack thereof).
author Rob Landley <rob@landley.net>
date Mon, 03 Dec 2007 20:05:57 -0600
parents 25447caf1b4b
children 9dc48c97d6f9
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1 /* oneit.c, tiny one-process init replacement.
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2 *
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3 * Copyright 2005, 2007 by Rob Landley <rob@landley.net>.
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4 *
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5 * Not in SUSv3.
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6 */
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7
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8 #include "toys.h"
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9 #include <sys/reboot.h>
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10
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11 // The minimum amount of work necessary to get ctrl-c and such to work is:
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12 //
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13 // - Fork a child (PID 1 is special: can't exit, has various signals blocked).
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14 // - Do a setsid() (so we have our own session).
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15 // - In the child, attach stdio to /dev/tty0 (/dev/console is special)
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16 // - Exec the rest of the command line.
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17 //
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18 // PID 1 then reaps zombies until the child process it spawned exits, at which
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19 // point it calls sync() and reboot(). I could stick a kill -1 in there.
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20
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21 void oneit_main(void)
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22 {
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23 int i;
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24 pid_t pid;
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25
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26 // Create a new child process.
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27 pid = vfork();
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28 if (pid) {
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30 // pid 1 just reaps zombies until it gets its child, then halts the system.
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31 while (pid!=wait(&i));
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32 sync();
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33 reboot(toys.optflags ? RB_POWER_OFF : RB_AUTOBOOT);
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34 }
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36 // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
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37 setsid();
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38 for (i=0; i<3; i++) {
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39 close(i);
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40 open("/dev/tty0",O_RDWR);
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41 }
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42
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43 // Can't xexec() here, because we vforked so we don't want to error_exit().
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44 toy_exec(toys.optargs);
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45 execvp(*toys.optargs, toys.optargs);
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46 _exit(127);
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47 }