Colours with Linux terminals Thorbjørn 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 . 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 ). 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="" 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 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 -- Thorbjørn Ravn Andersen