View Source: UnicodeNotes - Waikato Linux Users Group

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Traditionally, computers have used [ASCII], a set of 127 characters, as a result of English and American heritage. Every character can be represented with a single byte. Eventually, different countries came up with their own encodings, using the same bytes to represent different characters. For example, in a common "Western" encoding, the byte 0xFD means a Y with an acute accent, while in a common Turkish encoding, the byte 0xFD means a dotless i. And this is just for Latin-style encodings, without the thousands of characters needed by Asian languages.

With computers taking over the world, something called "Unicode" was developed that (attempts to) assign a unique number to most separate characters in most languages. By convention the number is it written in hexadecimal with “U+” prepended; this is called a codepoint. So Latin y with acute “ý” has the codepoint U+00FD, while a Latin dotless i “ı” has the codepoint U+0131. [UTF-8] (see the [utf-8(7)] ManPage) is a method of encoding codepoints in a backwards-compatible way with [Legacy] systems that use [ASCII] or Latin characters. The first 256 Unicode characters are identical to Western Latin, of which the first 127 are identical to [ASCII]. All [ASCII] characters are represented exactly the same way in [UTF-8]. See the [UTF-8 FAQ | http://www.cl.cam.ac.uk/~mgk25/unicode.html|http://www.cl.cam.ac.uk/~mgk25/unicode.html].

!!! Creating accented characters

QWERTY keyboards for English speakers obviously don't have separate keys for accented characters like other languages do. However, there are still relatively easy ways to get characters into your applications:
# Use a ‘character-picker’ applet or similar in your desktop environment. For example, in GNOME you can add a panel applet called "character palette" that offers a customisable variety of common non-ascii characters that you can click on to insert into your clipboard.
# Use a [“compose” key|ComposeKey]. For example, in GNOME's keyboard preferences settings you can assign a key to be the Compose key. If the Right Alt key is the compose key, then pressing right alt + ' will make the next character have an ' accent above it, if that is a valid combination. Eg "Compose+`, e" results in è, "Compose+~~, n" results in ñ (you have to press compose + shift + ` to get the ~~), and so on.

!!! Converting Text

To convert between unicode (eg utf-8 or utf-16), use the iconv command. The -t argument is the "to" encoding and -f is the "from" encoding. For example
  $ iconv -t utf-8 -f iso-8859-1 < somefile.txt > somefile-utf8.txt
This is a front end to the iconv(3) library (libiconv) that many recent programs use for handling character encoding and conversion.

!!! Setting up a [UTF-8] environment in Linux

!! Terminals

! Testing your terminal

To test if your terminal already supports UTF-8, try running the following command:

 <pre>
 $ perl -e 'print chr(195) . chr(137) . "\n"'
 É
 </pre>

Copy the following text from this page and paste it into your terminal:

<verbatim>
echo Árvíztűrő tükörfúrógép
</verbatim>

If everything is working, you should see it both on the shell's input line and in the xterm's output. If it doesn't work, then the problem might be with the terminal, with the locale, or the lack of a fixed font that has those characters.

Some shells (notably zsh(1)) can't cope with it (and gets confused if you start moving the cursor over the text), although xterm will still print the output fine.
Bash copes with it just fine too.

! Setting up xterm for UTF-8

To turn on UTF-8 support in xterm (it must have been compiled with utf-8 support, xterm version 145 or later), you must invoke xterm with the “<tt>-u8</tt>” option.

To turn on UTF-8 support in gnome-terminal, you print a certain escape sequence to the terminal: “<tt>/bin/echo -ne '\033%G'</tt>”

You will also need an X11 font that has the unicode characters you want to display. However, if your distribution comes with utf-8 enabled terminals, then it will almost certainly come with a decent default font. Try “<tt>xlsfonts | grep iso10646</tt>” to see unicode fonts you have access to. You should see some listed for "misc-fixed", which is the default font used by terminals.

If you don't specify a font when you start xterm, it will default to "fixed". This font is an "alias" – for the specific font that it maps to, look in <tt>/usr/share/fonts/misc/fonts.alias</tt> (or <tt>/usr/X11R6/lib/fonts/misc/fonts.alias</tt> for [XFree86] users):

 <verbatim>
 fixed        -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso8859-1
 </verbatim>

You should change that to end with "-iso10646-1" instead, if you have a unicode version of the font installed. If you don't have administrator rights, you can always make your own alias file, eg put

 <verbatim>
 fixed        -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso10646-1
 </verbatim>

into a file such as <tt>~~/.fonts/fonts.alias</tt> and then put this directory as the first directory on your font path:

 <verbatim>
 xset +fp $HOME/.fonts/fonts.alias
 </verbatim>

Now any new xterms should be able to display more non-[ASCII] characters.

Recent versions of xterm (eg v187) create accented Latin characters if you press a letter while the Alt key is pressed (eg alt+x gives an "ø" character). This will screw up any text-mode apps that expect alt to do something different (like emacs in text-mode). If you want the old-style behaviour, add
  XTerm.vt100.metaSendsEscape:  true
to your $HOME/.Xdefaults file, or run
 echo 'XTerm.vt100.metaSendsEscape:  true' | xrdb -merge
from a command line. (It will take effect for new xterms).

Also, you need to re-map the Alt key to be Meta. Add “

  <verbatim>
  keysym Alt_L = Meta_L
  </verbatim>

to your <tt>~~/.Xmodmap</tt> file (which should be sourced on login), or run

  <verbatim>
  xmodmap -e 'keysym Alt_L = Meta_L'
  </verbatim>

! UXterm

The program uxterm is a shell script wrapper that sets up the locale properly then runs xterm with the right parameters.

! rxvt

There is a unicode enabled version of rxvt, [uxrvt | http://software.schmorp.de/pkg/rxvt-unicode.html].

<verbatim>
urxvt -fn "xft:Bitstream Vera Sans Mono:pixelsize=16"
</verbatim>

!! locale

It's a good idea to set some environment variables to tell applications
what [language and encoding|LocaleName] you prefer. In NewZealand, you should do
something like
 $ LC_ALL=en_NZ.UTF-8 ; export LC_ALL

(This requires your system to have the correct support for this locale;
if it doesn't then the administrator can add "en_NZ.UTF-8 UTF-8" to
/etc/locale.gen and run locale-gen(8), which is in the "locales"
package.)

The system administrator can make this the default by putting
 LC_ALL=en_NZ.UTF-8
into /etc/environment (create it if it doesn't already exist - Note that this file might possibly be Debian-specific).

As well as getting utf-8 support, this has the added advantage that locale-aware applications
will use the correct currency symbol, unit separator, date formatting etc for your locale.
(Eg, MozillaMail will show dates as dd/mm/yyyy instead of the default US mm/dd/yyyy)

If you don't have a friendly administrator or can't otherwise get root permissions, you should still be
able to generate a locale yourself if it isn't already installed:

1. generate a locale giving an encoding, a locale, and an output directory:
<verbatim>
  mkdir -p ~/pkg/locale/ && localedef -f UTF-8 -i en_NZ ~/pkg/locale/en_NZ.UTF-8
</verbatim>
2. Set your LOCPATH environment variable to point to the correct directory
<verbatim>
  echo 'export LOCPATH=~/pkg/locale' >> ~/.bashrc
  export 'export LC_ALL=en_NZ.UTF-8' >> ~/.bashrc
</verbatim>

!!The [less(1)] program

[less(1)] looks for an environment variable to determine what is a printable character. The following tells less to display characters for utf-8:
 $ LESSCHARSET=utf-8
 $ export LESSCHARSET
This is not absolutely necessary -- you can give less the "-r" option to display raw characters, instead of octal codes. Or once you a viewing a file in less, you can type "-" then "r" to toggle this display on and off. If you have the environment variable set, then you can't toggle it. (Sometimes it is useful to see the raw utf-8 codes, for development purposes).

!! Perl
perl 5.8 has significantly improved unicode/utf-8 handling over earlier versions. See the perllocale(1) and perlunicode(1) man pages.
Once set to use unicode, commands like lc/uc (lower/upper case) and
RegularExpression character classes (space/printable/upper/lower etc)
will work as you'd expect.

Perhaps the most important tip is that by default, filehandles (including stdin(3)) are assumed to be Latin1/iso-8859-1 (most
likely for backwards-compatibility?). Add
  use encoding 'utf8';
to your script to change the default string encoding.

!! emacs

If you do want alt+letters to create accented characters, __don't__ use xmodmap to remap Alt to Meta (as described above), and add:
 (set-keyboard-coding-system 'utf-8)
 (set-terminal-coding-system 'utf-8)
to your $HOME/.emacs file.

!! vim

See the VimNotes page.

!! Mail clients

Mozilla has great charsets support, being so new. Netscape >= 4.05 has some support, but does have troubles. Mutt can do utf-8, but I haven't been able to get it to show the headers summary correctly. I don't know about kmail, balsa, or evolution, but my guess is that they are new enough to have good support.

!! X Fonts

The easiest thing I've found to do is to get some of the excellent Microsoft true type fonts working under linux as they have put quite a bit of work into internationalisation and fonts.
If they aren't installed system wide, you can install them into $HOME/.fonts and programs using fontconfig (most modern graphical programs) will automatically find them.
At the very least, "Courier new" and "Times New Roman" are good TTF fonts to use. I personally also like "Verdana" as a sans-serif font.

!! File systems (Samba)

I copied a bunch of files with "non-printable" UTF-8 characters (Árvíztűrő tükörfúrógép etc) from a Samba share, using cygwin's rsync under Windows, to a vfat drive.  Somewhere along the way, the encoding got changed from UTF-8 and the end result was that my ő's changed to bad squiggles or question marks, depending on what program you lookd at them with.

The [convmv|http://j3e.de/linux/convmv/] utility lets you do a bulk conversion of character sets in file names:

<verbatim>
./convmv -r -f latin1 -t utf8 --notest /array/images/mp3/albums/*
</verbatim>

fixed my problem.  Thanks to [the Unicode/charsets section of the Samba HOWTO|http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/unicode.html].

For the "opposite" problem --- that is, you have a windows machine with a share that is samba-mounted onto a linux client, and the non-ascii characters are getting munged --- you  need to give samba some mount options: <tt>iocharset=utf8</tt> tells samba to use a utf-8 encoding when presenting filenames to linux applications, and <tt>codepage=<i>foo</i></tt> tells samba which encoding the windows machine is using. If your accents are getting screwed up, try <tt>codepage=850</tt>, eg.:

  <verbatim>
  smbmount //servername/sharename /mnt/point -o codepage=cp850,iocharset=utf8,password=$pass
  </verbatim>

----
CategoryNotes
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Last edited on Monday, June 1, 2009 7:58:09 pm by LawrenceDoliveiro
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