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setlogcons.c 2.0 KB

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  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: select PLATFORM_LINUX
  15. //config: help
  16. //config: This program redirects the output console of kernel messages.
  17. //applet:IF_SETLOGCONS(APPLET_NOEXEC(setlogcons, setlogcons, BB_DIR_USR_SBIN, BB_SUID_DROP, setlogcons))
  18. //kbuild:lib-$(CONFIG_SETLOGCONS) += setlogcons.o
  19. //usage:#define setlogcons_trivial_usage
  20. //usage: "[N]"
  21. //usage:#define setlogcons_full_usage "\n\n"
  22. //usage: "Pin kernel output to VT console N. Default:0 (do not pin)"
  23. // Comment from kernel source:
  24. /* ...
  25. * By default, the kernel messages are always printed on the current virtual
  26. * console. However, the user may modify that default with the
  27. * TIOCL_SETKMSGREDIRECT ioctl call.
  28. *
  29. * This function sets the kernel message console to be @new. It returns the old
  30. * virtual console number. The virtual terminal number 0 (both as parameter and
  31. * return value) means no redirection (i.e. always printed on the currently
  32. * active console).
  33. */
  34. #include "libbb.h"
  35. int setlogcons_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  36. int setlogcons_main(int argc UNUSED_PARAM, char **argv)
  37. {
  38. char *devname;
  39. struct {
  40. char fn;
  41. char subarg;
  42. } arg = {
  43. 11, /* redirect kernel messages (TIOCL_SETKMSGREDIRECT) */
  44. 0
  45. };
  46. if (argv[1])
  47. arg.subarg = xatou_range(argv[1], 0, 63);
  48. /* Can just call it on "/dev/tty1" always, but...
  49. * in my testing, inactive (never opened) VTs are not
  50. * redirected to, despite ioctl not failing.
  51. *
  52. * By using "/dev/ttyN", ensure it is activated.
  53. */
  54. devname = xasprintf("/dev/tty%u", arg.subarg);
  55. xioctl(xopen(devname, O_RDONLY), TIOCLINUX, &arg);
  56. return EXIT_SUCCESS;
  57. }