BL(1)                       General Commands Manual                      BL(1)

     bl — blinkenlights: blink keyboard LEDs

     bl [-rlbckNCS] [-d delay] device

     bl blinks the keyboard LEDs: the Num Lock, the Caps Lock, and the Scroll

     The options are:

     -l    lights blink from left to right.

     -r    lights blink from right to left.

     -b    lights bounce back and forth.  This is the default mode.

     -c    lights converge to the center, ie blink the Num and Scroll Lock,
           then the Caps Lock.

     -k    all LEDs blink randomly.

     -N    only Num Lock LED blinks.

     -C    only Caps Lock LED blinks.

     -S    only Scroll Lock LED blinks.

     -d    delay between blinks.  The delay must be given in microseconds.
           The default delay is 125000 microseconds.  Use this option to speed
           up, or slow down the blinking.

           device without the "/dev/" that you are logged in on.  These can
           only be virtual console devices.  If you are running X, use the
           virtual console that the X server is running on as the device.

     bl -k -d 100000 tty3

     Run blinkenlights on tty3, with a delay of 100000 microseconds, and blink
     the LEDs randomly.

     (from the jargon file, available on

     :blinkenlights: /blink'*n-li:tz/ n. Front-panel diagnostic lights on a
     computer, esp. a {dinosaur}.  Derives from the last word of the famous
     blackletter-Gothic sign in mangled pseudo-German that once graced about
     half the computer rooms in the English-speaking world.  One version ran
     in its entirety as follows:

                   ACHTUNG!  ALLES LOOKENSPEEPERS!  Das computermachine
          ist nicht fuer gefingerpoken und mittengrabben.  Ist easy schnappen
          der springenwerk, blowenfusen und poppencorken mit spitzensparken.
          Ist nicht fuer gewerken bei das dumpkopfen.  Das rubbernecken
          sichtseeren keepen das cotten-pickenen hans in das pockets muss;
          relaxen und watchen das blinkenlichten.

     This silliness dates back at least as far as 1959 at Stanford University
     and had already gone international by the early 1960s, when it was
     reported at London University's ATLAS computing site.  There are several
     variants of it in circulation, some of which actually do end with the
     word `blinkenlights'.

     In an amusing example of turnabout-is-fair-play, German hackers have
     developed their own versions of the blinkenlights poster in fractured
     English, one of which is reproduced here

          This room is fullfilled mit special electronische equippment.
          Fingergrabbing and pressing the cnoeppkes from the computers is
          allowed for die experts only!  So all the "lefthanders" stay away
          and do not disturben the brainstorming von here working
          intelligencies.  Otherwise you will be out thrown and kicked
          anderswhere!  Also: please keep still and only watchen astaunished
          the blinkenlights.

     When run on virtual consoles under older kernel versions (1.1.64 and
     older), the state of the Caps Lock and Num Lock changes with the LED.
     There is no problem if you are running X windows.

     Greg Hankins <>

     Copyright (C) 1994 - 1996 Greg Hankins

     bl is free software; you can redistribute it and/or modify it under the
     terms of the GNU General Public License as published by the Free Software
     Foundation; either version 2, or (at your option) any later version.

     bl is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

     You should have received a copy of the GNU General Public License along
     with bl; see the file COPYING.  If not, write to the Free Software
     Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

Linux                          February 17, 1996                         Linux