If you want to remap more than a couple keys, it sounds like you want to create a custom keyboard layout, a question which has been asked here before:
On the other hand, it isn't too hard to remap a few keys. Let's do the ones you asked for.
The xmodmap command can be used to remap the keyboard. For example, for the mappings you mention, create a .Xmodmap file in your home directory (note that I'm using >> rather than >, so it appends to rather then replaces the file):
$ echo keysym Alt_R = Mode_switch >> ~/.Xmodmap
$ echo keysym C = c C ccedilla Ccedilla >> ~/.Xmodmap
$ echo keysym U = u U udiaeresis Udiaeresis >> ~/.Xmodmap
... where 'ccedilla' is ç and udiaeresis is ü (both of which I just entered using this method, though I personally prefer the compose key method). I'll explain this in more detail below.
If you want these settings to be used every time you start the Ubuntu GUI (i.e. X server), you should then create (or edit) a file called .xinitrc in your home directory, and add this line (if it's not already there, which it probably isn't): xmodmap ~/.Xmodmap
You can also type xmodmap ~/.Xmodmap from your terminal to test your settings.
Note that there is no simple way to tell xmodmap to "undo" mistakes other than restarting the X server (if you've made them load automatically via .xinitrc, you'll need to fix .Xmodmap first)! However, you may be able to reset things to defaults by using setxkbmap -layout us (changing 'us' to whatever is appropriate for your normal layout).
Tips: To experiment with xmodmap mappings, you can run the commands one at a time, from the command line, e.g.:
$ xmodmap -e 'keysym U = u U udiaeresis Udiaeresis >> ~/.Xmodmap'
And you can use xmodmap -pke to show the current keymappings, or just xmodmap -p to show the modifier (Alt, Ctrl, etc.) mappings.
For a list of keysyms that you can remap, see this (which is where I found 'ccedilla' etc.)
http://www.in-ulm.de/~mascheck/X11/keysyms.txt
As promised, here is a brief explanation of the 3 lines I suggested putting in your .Xmodmap:
The first line will ensure that your right Alt key is treated as AltGr, as it already is on certain international keyboards. Unless you are in the USA you probably don't need that line.
The 2nd and 3rd lines remap the C and U keys, respectively.
You'll note that there are 4, space-separated entries after the '=' sign on each line. Here's what they mean:
- The 1st is what you want the key to produce when you press it alone (i.e. a the 'c' key enters a lowercase 'c').
- The 2nd is what to produce with the shift key (Shift 'c' enters
uppercase 'C').
- The 3rd is what will be produced when you press the key with your newly-remapped right Alt key
- The 4th defines what to produce when you press the right Alt key, a Shift key, and the letter key.
Other resources/references:
And don't forget to look at the man pages:
$ man xmodmap
$ man xev
Best Answer
Yeah, it is possible to use the Unicode code directly in xkb keyboard layout definition files in
/usr/share/X11/xkb/symbols/or to use withkeysymusing this formatU####or0x100####.Example:
Or to define new keysym:
For permanent keysym, add to
~/.xmodmapfile:References: