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annotate toys/oneit.c @ 233:d4176f3f3835

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Zap toys/Config.in and instead create generated/Config.in from contents of toys/*.c. Move relevant info into comment at the top of each toys/*.c. Also convert more of Makefile into a thin wrapper around shell scripts that actually do the work. (Makefile is only still there for the user interface.)
author Rob Landley <rob@landley.net>
date Sat, 19 Jan 2008 17:08:39 -0600
parents 9dc48c97d6f9
children 163498bf547b
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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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9 config ONEIT
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10 bool "oneit"
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11 default y
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12 help
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13 usage: oneit [-p] [-c /dev/tty0] command [...]
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15 A simple init program that runs a single supplied command line with a
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16 controlling tty (so CTRL-C can kill it).
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18 -p Power off instead of rebooting when command exits.
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19 -c Which console device to use.
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21 The oneit command runs the supplied command line as a child process
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22 (because PID 1 has signals blocked), attached to /dev/tty0, in its
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23 own session. Then oneit reaps zombies until the child exits, at
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24 which point it reboots (or with -p, powers off) the system.
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25 */
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27 #include "toys.h"
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28 #include <sys/reboot.h>
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29
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30 // The minimum amount of work necessary to get ctrl-c and such to work is:
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31 //
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32 // - Fork a child (PID 1 is special: can't exit, has various signals blocked).
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33 // - Do a setsid() (so we have our own session).
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34 // - In the child, attach stdio to /dev/tty0 (/dev/console is special)
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35 // - Exec the rest of the command line.
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36 //
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37 // PID 1 then reaps zombies until the child process it spawned exits, at which
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38 // point it calls sync() and reboot(). I could stick a kill -1 in there.
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40 #define TT toy.oneit
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42 void oneit_main(void)
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43 {
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44 int i;
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45 pid_t pid;
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46
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47 // Create a new child process.
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48 pid = vfork();
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49 if (pid) {
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50
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51 // pid 1 just reaps zombies until it gets its child, then halts the system.
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52 while (pid!=wait(&i));
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53 sync();
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54 reboot(toys.optflags ? RB_POWER_OFF : RB_AUTOBOOT);
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55 }
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56
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57 // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
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58 setsid();
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59 for (i=0; i<3; i++) {
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60 close(i);
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61 xopen(TT.console ? TT.console : "/dev/tty0",O_RDWR);
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62 }
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63
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64 // Can't xexec() here, because we vforked so we don't want to error_exit().
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65 toy_exec(toys.optargs);
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66 execvp(*toys.optargs, toys.optargs);
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67 _exit(127);
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68 }