LXR busybox/console-tools/setlogcons.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * setlogcons: Send kernel messages to the current console or to console N
   4 *
   5 * Copyright (C) 2006 by Jan Kiszka <jan.kiszka@web.de>
   6 *
   7 * Based on setlogcons (kbd-1.12) by Andries E. Brouwer
   8 *
   9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  10 */
  11//config:config SETLOGCONS
  12//config:       bool "setlogcons (1.8 kb)"
  13//config:       default y
  14//config:       help
  15//config:       This program redirects the output console of kernel messages.
  16
  17//applet:IF_SETLOGCONS(APPLET_NOEXEC(setlogcons, setlogcons, BB_DIR_USR_SBIN, BB_SUID_DROP, setlogcons))
  18
  19//kbuild:lib-$(CONFIG_SETLOGCONS) += setlogcons.o
  20
  21//usage:#define setlogcons_trivial_usage
  22//usage:       "[N]"
  23//usage:#define setlogcons_full_usage "\n\n"
  24//usage:       "Pin kernel output to VT console N. Default:0 (do not pin)"
  25
  26// Comment from kernel source:
  27/* ...
  28 * By default, the kernel messages are always printed on the current virtual
  29 * console. However, the user may modify that default with the
  30 * TIOCL_SETKMSGREDIRECT ioctl call.
  31 *
  32 * This function sets the kernel message console to be @new. It returns the old
  33 * virtual console number. The virtual terminal number 0 (both as parameter and
  34 * return value) means no redirection (i.e. always printed on the currently
  35 * active console).
  36 */
  37
  38#include "libbb.h"
  39
  40int setlogcons_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  41int setlogcons_main(int argc UNUSED_PARAM, char **argv)
  42{
  43        char *devname;
  44        struct {
  45                char fn;
  46                char subarg;
  47        } arg = {
  48                11, /* redirect kernel messages (TIOCL_SETKMSGREDIRECT) */
  49                0
  50        };
  51
  52        if (argv[1])
  53                arg.subarg = xatou_range(argv[1], 0, 63);
  54
  55        /* Can just call it on "/dev/tty1" always, but...
  56         * in my testing, inactive (never opened) VTs are not
  57         * redirected to, despite ioctl not failing.
  58         *
  59         * By using "/dev/ttyN", ensure it is activated.
  60         */
  61        devname = xasprintf("/dev/tty%u", arg.subarg);
  62        xioctl(xopen(devname, O_RDONLY), TIOCLINUX, &arg);
  63
  64        return EXIT_SUCCESS;
  65}
  66