Colours with Linux terminals
Thorbj�rn Ravn Andersen, ravn@dit.ou.dk
$Date: 1996/04/27 16:56:15 $
Most Linux distributions have a 'ls' command that supports colours,
and it is often desired to have different colours than the default but
this 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 alternative software not included with
Slackware. The HTML version is also available from my own source
<http://www.dit.ou.dk/~ravn/colour-ls>.
1. Introduction
Most Linux distributions have a 'ls' command that supports colours,
and it is often desired to have different colours than the default but
this 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 alternative software not included with
Slackware.
This revision is a major rewrite from the initial release, including
information on xterms and kernel patching.
The information in here 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.
2. Which colours 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 -e "\t 40\t 41\t 42\t 43\t 44 45\t46\t 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 "30;40;1". The whole
ANSI selection sequence is then
ESC [ 3 0 ; 4 0 ; 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.
3. How to configure colours with ls
The standard Slackware setup creates the environment variable
LS_COLORS from the
$HOME/.dir_colors
system standard). The LS_COLORS looks like
LS_COLORS=:no=00:fi=00:di=01:ln=01;36:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:..
If you want a setup different from the standard, copy /etc/DIR_COLORS
to
$HOME/.dir_colors
seen with the script above. Use
eval `dircolors -t` # set up color-ls variables
to recalculate LS_COLORS with tcsh. See dircolors(1) for details.
Note: If you use a 'ls' from a version of Slackware before 2.2, you
should upgrade. It is buggy.
4. How to configure another default than 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" 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 you
are out of luck, well here is the gory details:
4.1. Xterm
Use one of
xterm -fg white -bg blue4
color_xterm -fg white -bg blue4
where 'color_xterm' supports the colour version of 'ls'. This
particular choice resembles the colours used on an SGI.
4.2. 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
strongly 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 1800, 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: the most
significant digit (the "1" in the colours) 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).
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:
4.2.1. /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 rlogin). This file is created by
/etc/rc.d/rc.S at boot time, and you should modify (around line 75)
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]${ESCAPE}[2J"> /etc/issue
echo Welcome to Linux `/bin/uname -a | /bin/cut -d\ -f3`. >> /etc/issue
This code will home the cursor, set the colour (here white on blue),
save this selection and clean the rest of the screen. The
modification takes effect after the next reboot. Remember to insert
the _literal_ escape character in the file with C-q in emacs or
control-v in vi, as apparently the sh used for executing this script
does not understand the /033 syntax.
4.2.2. /etc/profile or .profile
if [ "$TERM" = "console" ]; then
echo "\033[37;44m\033[8]" #
# or use setterm.
setterm -foreground white -background blue -store
fi
4.2.3. /etc/login or .login
if ( "$TERM" == "console" ) then
echo "\033[37;44m\033[8]"
# or use setterm.
setterm -foreground white -background blue -store
endif
4.3. 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.
If you encounter a successful combination, I would like to have it
here.
5. Software
All the information described here is assuming a Slackware
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.
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. You need the package plus a patch.
ftp://ftp.denet.dk/pub/gnu/fileutils-3.12.tar.gz
ftp://ftp.funet.fi/pub/Linux/sunsite/utils/file/color-ls-3.12.0.3.patch.gz
I have myself successfully compiled color-ls on Solaris, SunOS and
Irix. Note that the patch requires a recent version of the patch
program (pointers to source?) and you may find it the most easy to
untar and patch on a Linux system and then move the source.
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