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Linux Keyboard Setup Mini-Howto Stephen Lee, sl14@cornell.edu Version 1.3, 16 Sep 1995 This Mini-HOWTO document describes setting up the kernel and applica- tions to handle the Cursor control keys. 1. Introduction It has been annoying to me that cursor keys had not work consistently across different programs (and on different machines), so I took some time and tried to fix all that. Here I document my experience so others would not need to go through the same tedious cycle I did. I'm using Slackware 2.0.1, so pathnames to files might be different from yours if you are using a different distribution. Some of the material here appeared in an earlier ``BackSpace Mini- HOWTO''. Although the method described there still works, I consider this a better solution. 1.1. Typography o This is a program name. o This is a ``command'' you'd type on a keyboard. o This is a <Key> on the keyboard. eg. <BackSpace>, <Delete>, <Shift-l>, <Ctrl-q> etc. o This is an [X11 Keysym] which you can use for mapping keys under X. eg. [BackSpace], [Delete], [Left], [Home] etc. 1.2. Terminalogy ESC ASCII character 0x1B. BS ASCII character 0x08, or control-h. DEL ASCII character 0x7F. ^D ASCII character 0x04, or control-d. VC A Linux Virtual Console. 1.3. Acknowledgements Thanks to the following people who commented on my ``BackSpace Mini- HOWTO'': John Copella, Andrew Rakowski, Dr. Jacques Gelinas, Michael Bischoff, Topher Hughes, Chuck Meyer, Alexis Kotte, and especially Ted Stern and Steve Dunham. Thanks to Jamie Zawinski from Netscape Communications for pointing out the correct fix for the Backspace problem in Motif applications, and for the xkeycaps(1) program. 2. Non-X configuration I assume you came from the DOS world like I did, and is used to the mapping of function that <BackSpace> deletes character to the left of the cursor and <Delete> deletes character on top of the cursor. Under a shell, the most intuitive mapping is <BackSpace> -> BS and <Delete> -> DEL. This is fine unless you want to use EMACS. EMACS map <Ctrl-h> to its help function, which, under ASCII, is unfortunately BS. So each time you want to erase a character backwards, you invoke the help system. Also, DEL under Emacs deletes BACKWARDS, like what you'd expect for BS. One choice is to remap the keys under Emacs. Unfortunately you'll lose the ``<Ctrl-h> = help'' mapping. So, I decided to map <BackSpace> -> DEL. This leaves BS for use by <Ctrl-h> in Emacs. So, now what shall we do for the <Delete> key? In a previous verion of this document I used ^D, which works under both Emacs and csh/tcsh as a ``Delete character on cursor'' function. But since then I've found a better solution. The kernel by default maps <Delete> as the VT100 ``Remove'' key sequence (``ESC[3~''). It is not hard to teach Emacs and tcsh to recognize it. The advantage is that you can bind it differently than <Ctrl-d> in programs. Also, it is more consistent if you also map other cursor control keys. The disadvantage is that you might not be able to use it in some application which you can't bind key sequences (but than apply to the <Delete> -> ^D binding as well). 2.1. Linux console Linux console key bindings are controlled by the kernel. The kernel by default generates the correct bindings for <Backspace> and <Delete>, so you should not need to change that. However, if you do, the following programs (in the 'kbd' package, which should come with Slackware already) affect the key bindings: showkeys ``showkeys'' shows the Linux keycode generated by a key. The keycode can then be used by loadkeys(1) to change the keymap. dumpkeys Shows the current keybindings. See the manual page for more detail. loadkeys ``loadkeys file'' loads keybindings from file ``file''. Note that this changes the key bindings for ALL virtual consoles. This is usually done at boot time in /etc/rc.d/rc.local. You can start with one of the keytable files in /usr/lib/kbd/keytables/*.map and edit that. The one that is compiled into your kernel would be /usr/src/linux/drivers/char/defkeymap.map if you have the kernel source. The format of the file is described in the keytables(5) manual page. The keys of particular interest are <BackSpace> (keycode 14), <Delete> (111). setmetamode ``setmetamode'' controls whether the keystroke <Alt-x>, where x is some key, would send the keycode M-x or the key sequence ESC followed by x. This is virtual-console-specific, you can have different setting in different virtual consoles. 2.2. tty (including the Linux console) ``stty erase <ch>'' tells the terminal what character your <BackSpace> key generates. It does NOT change your key bindings. If you map <BackSpace> to DEL then do a ``stty erase '^H''' it won't magically changes your <BackSpace> key to generate ^H; it would only confuse your computer. To correctly set your terminal ``erase'' character to DEL, type ``stty erase '^?''' (where ^? can be '^' followed by '?' or <Ctrl-v> <BackSpace>) at your shell prompt. You might want to put this in your $(HOME)/.cshrc or $(HOME)/.profile. Note: although csh/tcsh treats BS and DEL the same way, other programs don't. So your mapping might seem to work under csh/tcsh but you get wierd stuff like ^? under some programs. Solution: remember the ``stty'' command above. 2.3. Shells 2.3.1. tcsh tcsh provides the command ``bindkey'' for binding keys: bindkey lists all current bindings. bindkey ``str'' function binds input string ``str'' to ``function''. A list of tcsh functions can be obtained by ``bindkey -l''. bindkey -k <up | down | left | right> function binds an arrow key to ``function''. Example: To bind cursor control keys, put this in $HOME/.cshrc: ______________________________________________________________________ if ($term == "xterm" || $term == "vt100" \ || $term == "vt102" || $term !~ "con*") then # bind keypad keys for console, vt100, vt102, xterm bindkey "\e[1~" beginning-of-line # Home bindkey "\e[2~" overwrite-mode # Ins bindkey "\e[3~" delete-char # Delete bindkey "\e[4~" end-of-line # End endif ______________________________________________________________________ See the man page for tcsh(1) for a complete description. Example: You can have 4DOS-style command history under tcsh with the tcsh function-pair history-search-backward (Meta-p) and history- search-forward (Meta-n). Typing ``abc<Meta-p>'' will only show lines in history that start with ``abc''. Also, function magic-space expands ! histories as you type, and I prefer them over the default so I bound them to the up/down arrow keys and space: ______________________________________________________________________ bindkey -k up history-search-backward bindkey -k down history-search-forward bindkey " " magic-space ______________________________________________________________________ 2.3.2. bash The ``.inputrc'' file contains the list of key bindings to functions. For example, if you put the following line in $HOME/.inputrc: ______________________________________________________________________ "\e[1~": beginning-of-line "\e[3~": delete-char "\e[4~": end-of-line ______________________________________________________________________ It will map the <Home>, <Delete>, and <End> keys respectively to the corresponding functions. You might also need the following line if your <BackSpace> key sends the ASCII DEL: ______________________________________________________________________ DEL: backward-delete-char ______________________________________________________________________ You probably don't need it (I don't), but it's worth a try if you run into trouble. 2.4. Editors 2.4.1. Emacs 19 Emacs 19 provides the elisp function define-key for binding keys. You can bind a key sequence to a function key like this in $(HOME)/.emacs: ______________________________________________________________________ ;; map function keys on PC keyboard (setq term (getenv "TERM")) (if (or (string= "xterm" term) (string= "con" (substring term 0 3)) ; linux consoles (string= "vt100" term) (string= "vt102" term)) (progn (defun my-setkey-hook () (define-key function-key-map "\e[1~" [home]) (define-key function-key-map "\e[2~" [insert]) (define-key function-key-map "\e[3~" [delete]) (define-key function-key-map "\e[4~" [end]) ;; these are just my own sequences ;; so I can use the keys under Emacs (define-key function-key-map "\e[40~" [C-prior]) (define-key function-key-map "\e[41~" [C-next]) ;; function keys: use same mapping as xterm (define-key function-key-map "\e[11~" [f1]) (define-key function-key-map "\e[12~" [f2]) ;; ... (define-key function-key-map "\e[24~" [f12]) (define-key function-key-map "\e[25~" [S-f1]) (define-key function-key-map "\e[26~" [S-f2]) ;; ... (define-key function-key-map "\e[39~" [S-f12]) ) (add-hook 'term-setup-hook 'my-setkey-hook) ) () ) ______________________________________________________________________ Note the function key names are all in lowercase. You can also bind function keys (or key sequences, but we won't be using that here) to a emacs command with global-set-key like this: ______________________________________________________________________ (global-set-key [delete] 'delete-char) (global-set-key [home] 'beginning-of-line) ; you might not want this (global-set-key [end] 'end-of-line) ; nor this (global-set-key [C-prior] 'beginning-of-buffer) (global-set-key [C-next] 'end-of-buffer) (global-set-key [f1] 'help-for-help) ;; ... (global-set-key [S-f12] 'info) ______________________________________________________________________ 2.4.2. vi Anybody want to write this? 2.5. Other Programs 2.5.1. less lesskey(1) allows you to map keys for the less(1) pager. Put the following lines in your $HOME/.lessrc (this is for VT100-like terminals): ______________________________________________________________________ ^[[A back-line ^[[B forw-line ^[[C next-file ^[[D prev-file ^[OA back-line ^[OB forw-line ^[OC next-file ^[OD prev-file ^[[6~ forw-scroll ^[[5~ back-scroll ^[[1~ goto-line ^[[4~ goto-end ______________________________________________________________________ replacing '^[' with the ESC character (ASCII 0x1B), then run ``lesskey .lessrc'' in your home directory. You can then use the cursor pad keys for scrolling text under less(1). 3. X configuration Under the X windows system, every key can have a different keysym assigned to it, instead of just an ASCII value of key sequence. Thus, X applications can distinguish easily between, for example, <Tab> (which generates the [Tab] keysym) and <Ctrl-i> (which generates the [i] keysym with the "Ctrl" modifier). One consequence is that we want <BackSpace> to generate the [BackSpace] keysym. However, on most systems <BackSpace> as well as <Delete> generate the [Delete] keysym by default due to the way the XFree86 server is written (it reads the settings from Linux's key map). This makes the two keys indistinguishable. This is the number 1 cause in the ``Backspace doesn't work in my X application'' problem. See the entry for xmodmap(1) or xkeycaps(1) for a fix. A list of keysyms can be found in <X11/keysymdef.h> (usually /usr/include/X11/keysymdef.h), without the XK_ prefix, and also /usr/lib/X11/XKeysymDB. Note X keysyms are case sensitive. There are several modifiers (like ``Shift'' and ``Ctrl'') that can be generated under X: Shift, Ctrl, Meta, Alt, Super and Hyper. Note that although ``Alt'' is present, most of the time the <Alt> key on the PC keyboard is bound to the ``Meta'' modifier; it works with more applications this way. 3.1. X server xev xev(1) allows you to see events generated on a window, including <KeyPress> and <KeyRelease> events where you can find the keycode for a particular key. Once the keycode is found for a key it can be mapped into a X11 keysym with xmodmap. xkeycaps From the README file: xkeycaps is a graphical front-end to xmodmap. It opens a window that looks like a keyboard; moving the mouse over a key shows what KeySyms and Modifier bits that key generates. Clicking on a key simulates KeyPress/KeyRelease events on the window of your choice. It is possible to change the KeySyms and Modifiers generated by a key through a mouse-based interface. This program can also write an input file for xmodmap to recreate your changes in future sessions. See the man page for more details. The latest version of xkeycaps is always ftpable from ftp.x.org. You can also get it from my web page at this place (http://www.netscape.com/people/jwz/). xmodmap One of the function of xmodmap(1) is to map X keycodes to keysyms. ``xmodmap <file>'' reads the keycode -> keysym table from the file ``file'' (usually named .xmodmaprc or .Xmodmap in the user's home directory). This is usually done by xinit(1) or startx(1) when X starts up. By default, Slackware loads the file $HOME/.Xmodmap if it is present; so putting the following two lines in it should fix most problems. Otherwise, read on. ________________________________________________________________ keycode 22 = BackSpace keycode 107 = Delete ________________________________________________________________ ``xmodmap -e "command"'' can be used to execute a single xmodmap command, for simple changes. For example, you can put the the following lines in $HOME/.xinitrc instead of using the $HOME/.Xmodmap file: ___________________________________________________________________ # map the <BackSpace> key to the [BackSpace] keysym. xmodmap -e "keycode 22 = BackSpace" # map the <Delete> key to the [Delete] keysym. xmodmap -e "keycode 107 = Delete" ___________________________________________________________________ (Warning: X exits when the last line of .xinitrc finishes, so if you don't have a .xinitrc before, you must put something that will continue to run (like the window manager or an xterm) at the end of .xinitrc, and don't put it in the background!) Lastly, you might generate a map file from your loadkey(1) *.map file using ``/usr/lib/kbd/keytables/mk_modmap foo.map > foo.xmap''; you need to remove all the ``compose'' command in the output. Note that <BackSpace> would be mapped to the [Delete] keysym if you start with the keymap provided, so be sure to edit foo.xmap for keycode 22 (BackSpace) and 107 (Delete). 3.2. X applications X applications are usually configurated via resources. User customizations are usually put in $HOME/.Xdefaults and loaded via ``xrdb -load $HOME/.Xdefaults'' in .xinitrc (again, see the warning in the xmodmap entry). 3.2.1. Terminal Emulators 3.2.1.1. xterm family Key mappings can be changed like this in $(HOME)/.Xresources: ______________________________________________________________________ *VT100.Translations: #override <Key>BackSpace: string(0x7F)\n\ <Key>Delete: string(0x1b) string("[3~")\n\ <Key>Home: string(0x1b) string("[1~")\n\ <Key>End: string(0x1b) string("[4~")\n\ Ctrl<Key>Prior: string(0x1b) string("[40~")\n\ Ctrl<Key>Next: string(0x1b) string("[41~") ______________________________________________________________________ This applies to most xterm-based emulators (xterm, color_xterm, kterm etc. but not rxvt). 3.2.1.2. rxvt There is apparaently no way to remap keys in rxvt except by patching the source. Any proof to the contrary would be welcome. 3.2.2. Editors 3.2.2.1. FSF Emacs 19 global-set-key can be used to map keys to Emacs commands. See the Emacs 19 entry in the non-X section. To find out what emacs symbol a key sends, press the key in question (in a scratch buffer so it won't clobber up your files) and then use the Emacs command view-lossage (usually <Ctrl-h> <l>) to see what the key generated. Usually the symbol is the X11 keysym in lowercase; for example, <Insert> (which generates the [Insert] keysym) would be [insert] in Emacs. <Shift-fkey>, <Ctrl-fkey>, <Meta-fkey> generates [S-fkey], [C-fkey], and [M-fkey] respectively. Combinations generate something like [C-M- fkey]. Other modifiers are s- for "Super", H- for "Hyper" and A- for "Alt". 3.2.2.2. XEmacs Again, use define-key or global-set-key. I believe both the [keysym] method as in FSF Emacs or 'keysym (like below) work. The method of specifying <Ctrl-fkey> etc. is different; both [(control fkey)] or '(control fkey) should work. But note that <Ctrl-A> is '(control a) while <Ctrl-Shift-A> is '(control A). Save '(shift fkey) for non- alphabet keys. ______________________________________________________________________ (define-key global-map 'delete 'delete-char) (define-key global-map 'backspace 'backward-delete-char-untabify) (define-key global-map '(control prior) 'fkey-beginning-of-buffer) (define-key global-map '(control next) 'fkey-end-of-buffer) (define-key global-map '(control home) 'fkey-scroll-right) (define-key global-map '(control end) 'fkey-scroll-left) (global-set-key 'f1 'help-for-help) (global-set-key 'f3 'isearch-forward) (global-set-key 'f4 'query-replace-regexp) (global-set-key '(shift f1) 'info) (global-set-key '(shift f3) 'isearch-backward) ______________________________________________________________________ Sometimes the <Delete> key doesn't delete forward after changing a major mode even if you remapped it like the above. Then you might need to remap it in the keymap for that major mode like the example below: ______________________________________________________________________ ;; ;; Lisp modes setup ;; (defun my-lisp-mode-common-hook () (define-key shared-lisp-mode-map 'backspace 'backward-delete-char-untabify) (define-key shared-lisp-mode-map 'delete 'delete-char) ) (add-hook 'lisp-mode-hook 'my-lisp-mode-common-hook) (add-hook 'emacs-lisp-mode-hook 'my-lisp-mode-common-hook) (add-hook 'lisp-interaction-mode-hook 'my-lisp-mode-common-hook) ______________________________________________________________________ 3.2.3. Other Programs 3.2.3.1. Motif applications (e.g. Mosaic, Netscape) <BackSpace> should work in Motif applications if it generates the [BackSpace] keysym. See the entry for xmodmap(1). Previous version of this document suggested a fix using *XmText.translations or *XmTextField.translations resources. This is not recommended anymore as it would break other things. See the netscape FAQ for X (http://home.netscape.com/eng/mozilla/1.1/faq_navx.html) 4. For more information ``kbd.FAQ'' in the kbd package (ftp://sunsite.unc.edu/pub/Linux/system/Keyboards/kbd-0.89.tar.gz) contains more examples on remapping the keyboard. Man pages for the programs mentioned above are good sources of information, especially xterm(1x), xmodmap and stty(1). Info pages for Emacs tells you how to remap keys under it; use ``emacs -f info'' to read them. ``Keystroke-mini-HOWTO (ftp://sunsite.unc.edu/pub/Linux/doc/HOWTO/mini/Keystroke)'' describes a way to assign special action to some of the keys on the keyboard. ``the netscape FAQ (http://home.netscape.com/eng/mozilla/1.1/faq_navx.html#x12)'' has a solution for the ``Backspace doesn't work in Netscape'' problem.