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annotate toys/other/oneit.c @ 653:2986aa63a021

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Move commands into "posix", "lsb", and "other" menus/directories.
author Rob Landley <rob@landley.net>
date Sat, 25 Aug 2012 14:25:22 -0500
parents toys/oneit.c@2a003d86d805
children 6df4ccc0acbe
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d4176f3f3835 Zap toys/Config.in and instead create generated/Config.in from contents of
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1 /* vi: set sw=4 ts=4:
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2 *
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3 * oneit.c, tiny one-process init replacement.
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4 *
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5 * Copyright 2005, 2007 by Rob Landley <rob@landley.net>.
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6 *
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7 * Not in SUSv3.
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8
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93223118c813 Option parsing: stopearly is now a ^ prefix (not +), and an option string with
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9 USE_ONEIT(NEWTOY(oneit, "^<1c:p", TOYFLAG_SBIN))
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10
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11 config ONEIT
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12 bool "oneit"
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13 default y
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14 help
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15 usage: oneit [-p] [-c /dev/tty0] command [...]
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16
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17 A simple init program that runs a single supplied command line with a
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18 controlling tty (so CTRL-C can kill it).
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20 -p Power off instead of rebooting when command exits.
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21 -c Which console device to use.
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22
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23 The oneit command runs the supplied command line as a child process
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24 (because PID 1 has signals blocked), attached to /dev/tty0, in its
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25 own session. Then oneit reaps zombies until the child exits, at
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26 which point it reboots (or with -p, powers off) the system.
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27 */
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28
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29 #include "toys.h"
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30 #include <sys/reboot.h>
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31
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32 DEFINE_GLOBALS(
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33 char *console;
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34 )
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35
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36 #define TT this.oneit
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37
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38 // The minimum amount of work necessary to get ctrl-c and such to work is:
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39 //
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40 // - Fork a child (PID 1 is special: can't exit, has various signals blocked).
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41 // - Do a setsid() (so we have our own session).
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42 // - In the child, attach stdio to /dev/tty0 (/dev/console is special)
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43 // - Exec the rest of the command line.
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44 //
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45 // PID 1 then reaps zombies until the child process it spawned exits, at which
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46 // point it calls sync() and reboot(). I could stick a kill -1 in there.
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49 void oneit_main(void)
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50 {
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51 int i;
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52 pid_t pid;
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53
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54 // Create a new child process.
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55 pid = vfork();
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56 if (pid) {
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57
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58 // pid 1 just reaps zombies until it gets its child, then halts the system.
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59 while (pid!=wait(&i));
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60 sync();
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61
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62 // PID 1 can't call reboot() because it kills the task that calls it,
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63 // which causes the kernel to panic before the actual reboot happens.
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64 if (!vfork()) reboot((toys.optflags&1) ? RB_POWER_OFF : RB_AUTOBOOT);
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65 sleep(5);
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66 _exit(1);
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67 }
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68
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69 // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
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70 setsid();
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71 for (i=0; i<3; i++) {
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72 close(i);
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73 xopen(TT.console ? TT.console : "/dev/tty0",O_RDWR);
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74 }
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75
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76 // Can't xexec() here, because we vforked so we don't want to error_exit().
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77 toy_exec(toys.optargs);
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78 execvp(*toys.optargs, toys.optargs);
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79 _exit(127);
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80 }