We assume you have already adapted your Linux console and X11 configuration to your keyboard and locale. This is explained in the Danish/International HOWTO, and in the other national HOWTOs: Finnish, French, German, Italian, Polish, Slovenian, Spanish, Cyrillic, Hebrew, Chinese, Thai, Esperanto. But please do not follow the advice given in the Thai HOWTO, to pretend you were using ISO-8859-1 characters (U0000..U00FF) when what you are typing are actually Thai characters (U0E01..U0E5B). Doing so will only cause problems when you switch to Unicode.
I'm not talking much about the Linux console here, because on those machines on which I don't have xdm running, I use it only to type my login name, my password, and "xinit".
Anyway, the kbd-0.99 package ftp://sunsite.unc.edu/pub/Linux/system/keyboards/kbd-0.99.tar.gz and a heavily extended version, the console-tools-0.2.2 package ftp://sunsite.unc.edu/pub/Linux/system/keyboards/console-tools-0.2.2.tar.gz contains in the kbd-0.99/src/ (or console-tools-0.2.2/screenfonttools/) directory two programs: `unicode_start' and `unicode_stop'. When you call `unicode_start', the console's screen output is interpreted as UTF-8. Also, the keyboard is put into Unicode mode (see "man kbd_mode"). In this mode, Unicode characters typed as Alt-x1 ... Alt-xn (where x1,...,xn are digits on the numeric keypad) will be emitted in UTF-8. If your keyboard or, more precisely, your normal keymap has non-ASCII letter keys (like the German Umlaute) which you would like to be CapsLockable, you need to apply the kernel patch linux-2.2.9-keyboard.diff or linux-2.3.12-keyboard.diff.
You will want to use display characters from different scripts on the same screen. For this, you need a Unicode console font. The ftp://sunsite.unc.edu/pub/Linux/system/keyboards/console-data-1999.08.29.tar.gz package contains a font (LatArCyrHeb-{08,14,16,19}.psf) which covers Latin, Cyrillic, Hebrew, Arabic scripts. It covers ISO 8859 parts 1,2,3,4,5,6,8,9,10 all at once. To install it, copy it to /usr/lib/kbd/consolefonts/ and execute "/usr/bin/setfont /usr/lib/kbd/consolefonts/LatArCyrHeb-14.psf".
If you want cut&paste to work with UTF-8 consoles, you need the patch linux-2.3.12-console.diff from Edmund Thomas Grimley Evans and Stanislav Voronyi.
Don't hesitate to install Cyrillic, Chinese, Japanese etc. fonts. Even if they are not Unicode fonts, they will help in displaying Unicode documents: at least Netscape Communicator 4 and Java will make use of foreign fonts when available.
The following programs are useful when installing fonts:
The following fonts are freely available (not a complete list):
Application wishing to display text belonging to different scripts (like Cyrillic and Greek) at the same time, can do so by using different X fonts for the various pieces of text. This is what Netscape Communicator and Java do. However, this approach is more complicated, because instead of working with `Font' and `XFontStruct', the programmer has to deal with `XFontSet', and also because not all fonts in the font set need to have the same dimensions.
$ gunzip unifont.hex.gz
$ hex2bdf < unifont.hex > unifont.bdf
$ bdftopcf -o unifont.pcf unifont.bdf
$ gzip -9 unifont.pcf
# cp unifont.pcf.gz /usr/X11R6/lib/X11/fonts/misc
# cd /usr/X11R6/lib/X11/fonts/misc
# mkfontdir
# xset fp rehash
xterm is part of X11R6 and XFree86, but is maintained separately by Tom Dickey. http://www.clark.net/pub/dickey/xterm/xterm.html Newer versions (patch level 109 and above) contain support for converting keystrokes to UTF-8 before sending them to the application running in the xterm, and for displaying Unicode characters that the application outputs as UTF-8 byte sequence.
To get an UTF-8 xterm running, you need to:
$ cd .../ucs-fonts
$ cat quickbrown.txt
$ cat utf-8-demo.txt
A small program which tests whether a Linux console or xterm is in UTF-8 mode can be found in the ftp://sunsite.unc.edu/pub/Linux/system/keyboards/x-lt-1.18.tar.gz package by Ricardas Cepas, files testUTF-8.c and testUTF8.c.