Colours with Linux terminals
Thorbj�rn Ravn Andersen, ravn@dit.ou.dk
v1.4, 7 August 1997
Most Linux distributions have a 'ls' command for listing the contents
of a directory that can visually enhance their output by using differ�
ent colours, but configuring this to taste may not be a trivial task.
This document explains the various aspects and approaches of altering
the setup by configuring existing software, plus locations of alterna�
tive software usually not included with Slackware or RedHat, which may
be used on most versions of Unix. The HTML version is also available
from my own source at <http://www.mip.ou.dk/~ravn/colour-ls>.
1. Introduction
In recent years colour displays have become very common, and users are
beginning to exploit this by using programs that utilizes colours to
give quick visual feedback on e.g. reserved keywords in programming
languages, or instant notification of misspelled words.
As the Linux text console supports colour, the original GNU ls was
quickly modified to output colour information and included in
Slackware around version 2.0. Improved versions of these patches have
now migrated into the standard GNU distribution of ls, and should
therefore be a part of all new Linux distributions by now.
This revision is an update on a major rewrite from the initial
release, including information on xterms and kernel patching.
The information in this document has been confirmed on Redhat 4.1, and
was originally compiled with the 2.0.2 release of Slackware, and the
1.1.54 kernel. The kernel patch information was retrieved on
slackware 2.2.0 with the 1.2.13 kernel, and tcsh as the default shell,
and later confirmed with a 2.0.27 kernel. If you use any other
configuration, or unix version, I would appreciate a note stating your
operating system and version, and whether colour support is available
as standard.
2. Quickstart for the impatient
If you have a new distribution of Linux, do these modifications to
these files in your home directory. They take effect after next
login.
~/.bashrc:
alias ls="ls --color"
~/.cshrc:
alias ls 'ls --color'
That's it!
You may also want to do an ``eval `dircolors $HOME/.colourrc`'', to
get your own colours. This file is created with ``dircolors -p
>$HOME/.colourrc'' and is well commented for further editing.
3. Do I have it at all?
First of all you need to know if you have a version of ls which knows
how to colourize properly. Try this command in a Linux text console
(although an xterm will do):
% ls --color
(the % is a shell prompt):
If you get an error message indicating that ls does not understand the
option, you need to install a new version of the GNU fileutils
package. If you do not have an appropriate upgrade package for your
distribution, just get the latest version from your GNU mirror and
install directly from source.
If you do not get an error message, you have a ls which understands
the command. Unfortunately, some of the earlier versions included
previously with Slackware (and possible others) were buggy. The ls
included with Redhat 4.1 is version 3.13 which is okay.
% ls --version
ls - GNU fileutils-3.13
If you ran the ``ls -- color'' command on a Linux textbased console,
the output should have been colourized according to the defaults on
the system, and you can now decide whether there is anything you want
to change.
If you ran it in an xterm, you may or you may not have seen any colour
changes. As with ls itself, the original xterm-program did not have
any support of colour for the programs running inside of it, but
recent versions do. If your xterm doesn't support colours, you should
get a new version as described at the end of this document. In the
meantime just switch to textmode and continue from there.
4. Which colours is there to choose from?
This shell script (thanks to the many who sent me bash versions) shows
all standard colour combinations on the current console. If no
colours appear, your console does not support ANSI colour selections.
#!/bin/bash
# Display ANSI colours.
#
esc="\033["
echo -n " _ _ _ _ _40 _ _ _ 41_ _ _ _42 _ _ _ 43"
echo "_ _ _ 44_ _ _ _45 _ _ _ 46_ _ _ _47 _"
for fore in 30 31 32 33 34 35 36 37; do
line1="$fore "
line2=" "
for back in 40 41 42 43 44 45 46 47; do
line1="${line1}${esc}${back};${fore}m Normal ${esc}0m"
line2="${line2}${esc}${back};${fore};1m Bold ${esc}0m"
done
echo -e "$line1\n$line2"
done
The foreground colour number is listed to the left, and the background
number in the box. If you want bold characters you add a "1" to the
parameters, so bright blue on white would be "37;44;1". The whole
ANSI selection sequence is then
ESC [ 3 7 ; 4 4 ; 1 m
Note: The background currently cannot be bold, so you cannot have
yellow (bold brown) as anything but foreground. This is a hardware
limitation.
The colours are:
0 - black 4 - blue 3# is foreground
1 - red 5 - magenta 4# is background
2 - green 6 - cyan
3 - yellow 7 - white ;1 is bold
5. How to configure colours with ls
If you wish to modify the standard colour set built into ls, you need
your personal copy in your home directory, which you get with
cd ; dircolors -p > .coloursrc
After modifying this well-commented file you need to have it read into
the environment string LS_COLORS, which is usually done with
eval `dircolors .colourrc`
You need to put this line in your .bashrc/.cshrc/.tcshrc (depending on
your shell), to have it done at each login. See the dircolors(1)
manual page for details.
6. How to change the text-mode default from white-on-black
You will need to tell the terminal driver code that you want another
default. There exists no standard way of doing this, but in case of
Linux you have the setterm program.
"setterm" uses the information in the terminal database to set the
attributes. Selections are done like
setterm -foreground black -background white -store
where the "-store" besides the actual change makes it the default for
the current console as well. This requires that the current terminal
(TERM environment variable) is described "well enough" in the termcap
database. If setterm for some reason does not work, here are some
alternatives:
6.1. Xterm
One of these xterms should be available and at least one of them
support colour.
xterm -fg white -bg blue4
color_xterm -fg white -bg blue4
color-xterm -fg white -bg blue4
nxterm -fg white -bg blue4
where 'color_xterm' supports the colour version of 'ls'. This
particular choice resembles the colours used on an SGI.
6.2. Virtual console.
You may modify the kernel once and for all, as well as providing a
run-time default for the virtual consoles with an escape sequence. I
recommend the kernel patch if you have compiled your own kernel.
The kernel source file is /usr/src/linux/drivers/char/console.c around
line 1940, where you should modify
def_color = 0x07; /* white */
ulcolor = 0x0f; /* bold white */
halfcolor = 0x08; /* grey */
as appropriate. I use white on blue with
def_color = 0x17; /* white */
ulcolor = 0x1f; /* bold white */
halfcolor = 0x18; /* grey */
The numbers are the attribute codes used by the video card in
hexadecimal: the most significant digit (the "1" in the example
colours above) is the background; the least significant the
foreground. 0 = black, 1 = blue, 2 = green, 3 = cyan, 4 = red, 5 =
purple, 6 = brown/yellow, 7 = white. Add 8 to get "bright" colours.
Note that, in most cases, a bright background == blinking characters,
dull background. (From sjlam1@mda023.cc.monash.edu.au
<mailto:sjlam1@mda023.cc.monash.edu.au>).
You may also supply a new run-time default for a virtual console, on a
per-display basis with the non-standard ANSI sequence (found by
browsing the kernel sources)
ESC [ 8 ]
which sets the default to the current fore- and background colours.
Then the Reset Attributes string (ESC [ m) selects these colours
instead of white on black.
You will need to actually echo this string to the console each time
you reboot. Depending on what you use your Linux box for, several
places may be appropriate:
6.2.1. /etc/issue
This is where "Welcome to Linux xx.yy" is displayed under Slackware,
and that is a good choice for stand-alone equipment (and probably be a
pestilence for users logging in with telnet). This file is created at
boottime (Slackware in /etc/rc.d/rc.S; Redhat in /etc/rc.d/rc.local),
and you should modify lines looking somewhat like
echo ""> /etc/issue
echo Welcome to Linux `/bin/uname -a | /bin/cut -d\ -f3`. >> /etc/issue
to
ESCAPE="<replace with a single escape character here>"
echo "${ESCAPE}[H${ESCAPE}[37;44m${ESCAPE}[8]${ESCAPE}[2J"> /etc/issue
echo Welcome to Linux `/bin/uname -a | /bin/cut -d\ -f3`. >> /etc/issue
This code will home the cursor, set the colour (here white on blue),
save this selection and clean the rest of the screen. The
modification takes effect after the next reboot. Remember to insert
the _literal_ escape character in the file with C-q in emacs or
control-v in vi, as apparently the sh used for executing this script
does not understand the /033 syntax.
6.2.2. /etc/profile or .profile
if [ "$TERM" = "console" ]; then
echo "\033[37;44m\033[8]" #
# or use setterm.
setterm -foreground white -background blue -store
fi
6.2.3. /etc/login or .login
if ( "$TERM" == "console" ) then
echo "\033[37;44m\033[8]"
# or use setterm.
setterm -foreground white -background blue -store
endif
6.3. Remote login
You should be able to use the setterm program as shown above. Again,
this requires that the remote machine knows enough about your
terminal, and that the terminal emulator providing the login supports
colour. In my experience the best vt100 emulation currently available
for other platforms are:
� MS-DOS: MS-Kermit (free, not a Microsoft product)
� Windows 95/NT: Kermit/95 (shareware)
� OS/2: Kermit/95 (shareware). Note though that the
standard telnet understands colours and can be customized locally.
See <http://www.columbia.edu/kermit/> for details about Kermit.
7. Software
All the information described here is assuming a GNU/Linux
installation. If you have something else (like e.g. a Sun running X
or so) you can get and compile the actual software yourself.
The colour version of 'xterm' is based on the standard xterm source
with a patch available from any X11R6 site. The xterm distributed
with R6.3 is rumoured to have native colour support, but is untested
by me.
ftp://ftp.denet.dk/pub/X11/contrib/utilities/color-xterm-R6pl5-patch.gz
See the documentation if you use an older version of X. Note: I
haven't tried this myself!
of the several mirrors. Get at least version 3.13.
ftp://ftp.denet.dk/pub/gnu/fileutils-3.XX.tar.gz
I have myself successfully compiled color-ls on Solaris, SunOS and
Irix.
I would appreciate feedback on this text. My e-mail address is
ravn@dit.ou.dk <mailto:ravn@dit.ou.dk>
--
Thorbj�rn Ravn Andersen