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