=================== Keystroke-HOWTO, version 2.0 ====================

			Linux Keystroke HOWTO
			         by
		 Zenon Fortuna (zenon@netcom.com)


Version: 2.0						April 4th '95

INDEX
	0.	What is "Keystroke-HOWTO" ?
	1.	History of changes
	2.	Short description
	3.	Tools for keyboard driver modification
	4.	Modifying keytable file
	4.0	Example of keytable file modification
	4.1	Temporary modification of the keyboard setup
	4.2	Permanent modification
	5.	Example of the key_macro script
	6.	Comments
	7.	Further ideas ?

----------------------------------------------------------------------------
0.	What is "Keystroke-HOWTO" ?

	This document is for users, who want to assign special action to some
	of keys of the keyboard. The suggested method is to use the loadkeys(1)
	or to modify the defkeymap.c file and relink the kernel.

	This text does NOT discuss remapping of keyboard keys, e.g. Backspace
	or Delete keys. For informations about remapping of keys read the
	Backspace Mini-HOWTO written by Stephen Lee.

	The method described below was tested on Linux 1.2.1 release, packaged
	in the Slackware 2.2.0 distribution.


1.	History of changes

	April 4th '95	Version: 2.0
	   Adapted for the Linux 1.2.1:
	   - simple changes in suggested modification of the "my_keytable.map"
	   - modified "key_macro" example with /dev/vcs* screen dumping

	May   7th '94	Version: 1.0
	   The initial version of the "Keystroke-HOWTO", which worked for the
	   Linux 1.0


2.	Short description

	The Linux virtual terminal and keyboard drivers assume default keyboard
	mapping as defined in the drivers/char/defkeymap.c file of the kernel
	source. The 12 PC keyboard function keys may get strings assigned to
	their action. After pressing any of those function keys, perhaps
	modified with the Alt or Ctrl keys, the current virtual terminal
	adds the specific string to its input and output buffers, in effect
	emulating entry of this string as typed in from the keyboard.

	Setting an appropriate string for chosen function key, we can simplify
	execution of selected command, for example calling a Shell-script
	"/usr/local/bin/key_macro", which we can create and modify as desired.


3.	Tools for keyboard driver modification

	We may use loadkeys(1), dumpkeys(1) and showkey(1):
	  The loadkeys(1) utility helps to load new strings into the kernel
	keyboard buffers or prepares the new C-code to modify the kernel.
	  The dumpkeys(1) should be used to get the current keyboard mapping
	table for inspection or modification.
	  The showkey(1) may assist us to obtain the keycode of the selected
	function key.

	If your Linux system does not have these utilities, you may get them
	via anonymous ftp as kbd-0.89.tar.gz or kbd-0.90.tar.gz package from
		sunsite.unc.edu:/pub/Linux/system/Keyboards, or
		tsx-11.mit.edu:/pub/linux/sources/system
	You should use the GNU tar to extract the needed files.


4.	Modifying keytable file

	Linux kernel includes compiled defkeymap.c code, which is generated
	with the loadkeys(1) utility from a defkeymap.map file. Both files
	are included in the src/linux/drivers/char directory.

	We need to modify the defkeymap.map file, so let's make a local
	copy of it either by
		# cp defkeymap.map my_keytable.map
	or
		# dumpkeys > my_keytable.map

	There is also a large collection of different keytable files in the
	/usr/lib/kbd/keytables directory, from which "defkeymap.map" may be
	used as src/linux/drivers/char/defkeymap.map file on your system.

	The method which uses the dumpkeys(1) utility is recommended, because
	it may happen, that your kernel was already modified or generated
	for you with different defkeymap.map file than the one you can find.

	Lets read the contents of the my_keytable.map file: there are more
	than 300 lines of code, and we can find 3 groups of declarations:
	The first group consists of lines with the word "keycode", maybe
	prepended with additional words like "alt", "control", etc.
	The second group consists of lines with the word "string".
	The third group consists of lines with the word "compose".

	More about the keytables(5) syntax can be read with
		% man keytables


4.0	Example of keytable file modification

	As an example of assigning a macro-string to a function key stroke,
	let's make the "Ctrl-F1" to call our "/usr/local/bin/key_macro"
	Shell-script.

	First of all we should find out what is the keycode for the F1 function
	key.  We may use the showkey(1) utility to find the keycode with
	pressing F1.

	Instead we can search for the "F1" string in the "my_keytable.map" file
	to find the following line:

	keycode  59 = F1

	This suggests, that the keycode for the F1 function key is 59.
	This line defines also, that after pressing the F1 key the keyboard
	driver would send out the string denoted by the string-code "F1".
	To see the contents of this string, one can search for the "string F1"
	pattern, to find

	string F1 = "\033[[A"

	This means, that after pressing the F1 key, the keyboard driver sends
	the "Esc [ [ A" (without blank spaces).

	We shouldn't change this string, because some applications depend on
	this string as default action of the F1 function key.

	However, we may define the new action for Ctrl-F1, provided it is not
	reserved by your kernel for other special actions.
	To see the mappings of the F1 key modified with the Ctrl-, Shift- or
	other modes, we may inspect the "my_keytable.map" file with

		# grep 59 my_keytable.map

	In case when there is no line with "control keycode 59" we may use
	the Ctrl-F1 without problems. (when a line with the "shift control
	keycode 59" exists it is still OK)

	Let us add a following line to the "my_keytable.map" file:

		control keycode 59 = key_symbol

	where the "key_symbol" would define the action of the Ctrl-F1 key.
	The Linux 1.2.* allows a dynamic allocation of strings, but a name
	of the "key_symbol" may be picked up only from a fixed set of names.
	Between other names the key-symbols F1-F246 are allowed.
	For "my_keytable.map" on my system the F21 was unused, but you should
	inspect your "my_keytable.map" and choose a proper key-symbol.
	So, we may end up with a line

		control keycode 59 = F21

	Now we have to define the contents of the F21, adding a line

		string F21 = "/usr/local/bin/key_macro\n"

	In the summary, we made two changes to the original "my_keytable.map"
	file: we declared the new string F21, and we have declared
	that the Ctrl-F1 key will be calling the F21 contents.


4.1	Temporary modification of the keyboard setup

	Having properly modified "my_keytable.map" we can copy the changes
	to the kernel keyboard driver, using the loadkeys(1) utility:

	% loadkeys my_keytable.map

	The permission to modify the kernel keyboard driver is granted to
	everybody who has the read access to the "/dev/console" device.

	To verify that the intended changes were installed, we can use the
	dumpkeys(1) utility to check the F21 value, for example

	% dumpkeys | grep F21

	We may see:

	keycode 59 = F1		F11	Console_13	F21

	string F21 = "/usr/local/bin/key_macro\012"

	which is OK, because "\012", or LF, is equivalent to "\n".

	Now, pressing "Ctrl-F1" should call the "/usr/local/bin/key_macro"
	Shell-script, as intended. 


4.2	Permanent modification

	The changes to the kernel keyboard driver imposed by the loadkeys(1)
	last until the next reboot (or the next call to loadkeys).

	We can modify the /etc/rc.d/rc.local to call the loadkeys with our
	my_keytable.map file as an argument. Instead, we can modify the
	src/linux/drivers/char/defkeymap.c and re-link the kernel with
	new defaults.

	We should not modify the defkeymap.c manually, but rather generate
	it with the loadkeys(1) utility:

	# mv defkeymap.c defkeymap.c.ORIG
	# loadkeys --mktable my_keytable.map > defkeymap.c

	Then we should generate the new kernel, essentially changing directory
	to the root of the linux kernel source, and using the make(1).

	Finally, we should use the lilo(1) to install and boot our new kernel.


5.	Example of the key_macro script

	A particularly useful script for simple-key-stroke operation may be
	a Shell-script preparing, or printing, a screen dump.

	This example has changed since the version 1.0 of Linux, because
	of the changes in the Linux kernel, which does not provide the
	ioctl(0,TIOCLINUX) system call anymore.

	To read the virtual console screen dumps one should prepare first
	some device files. As "root" user we may create the following files:

		# mknod /dev/vcs1  c 7 1
		# mknod /dev/vcs2  c 7 2
		...
		# mknod /dev/vcs63 c 7 63

	Of course, it is sufficient to have only the /dev/vcs* files specific
	for the virtual consoles you are using.

	The code below should be regarded as an example of possible
	/usr/local/bin/key_macro file:

#!/bin/sh
#
# This is an example of useful key_macro script
#

VT_NUMBER=`tty|cut -c9-`
FILE=/tmp/vt$VT_NUMBER.dump
cp /dev/vcs$VT_NUMBER $FILE
echo SCREEN DUMP saved in $FILE
#
# Uncomment the line below if you want to print the resulted dump-file
# lpr $FILE


6.	Comments

	There is no practical limit on the sum the lengths of all strings
	which we would like to load to the keyboard driver. The previous fixed
	buffer of the length of FUNC_BUFSIZE (set to 512 bytes), has been
	replaced in the Linux 1.2.* by a strategy of dynamic buffer allocation
	... in chunks of 512 bytes each.

	The most recent copy of the Keystroke-HOWTO can be found in

		ftp.netcom.com: /pub/ze/zenon/linux/howto


7.	Further ideas ?

	In case you find anything worth adding to this document, please send
	your comments to zenon@netcom.com -- thanks (zf)