Features/256 Color Terminals
256 Color Terminals
Enable terminal programs to use the enhanced color capabilities of modern terminals by default.
I.E. increase their color options from the 8 colors at the top of this picture, to the other 256 displayed.
- Targeted release: Fedora 18
- Last updated: 2012-06-16
- Percentage of completion: 50%
Many terminal programs (like vim and ls for example) can take advantage of 256 color terminals,
and all xterms I know of support at least 256 colors and sometimes more.
So let's break through the artificial 8 color limit!
Also when preparing this page, while searching the net I noticed that Mac OS X Terminal's default $TERM value is xterm-256color since Lion 10.7 That will ease some of the compatibility issues noted below.
You can see vim's default appearance using the above expanded palette at:
Benefit to Fedora
By having 32 times more colors available gives much better scope for using more appropriate default colors. For example, users could set their terminal backgrounds to dark or light and have ls use colors that are appropriate to either.
Also more subtle and considered coloring can be used as discussed and depicted at: https://github.com/seebi/dircolors-solarized
This will be mainly configuration changes. I think the most easily configurable/maintainable option is to have a new /etc/profile.d/256color.sh file. That will keep the config central, and set things up in a standard way such that LS_COLORS will be set appropriately.
Here is my current version:
[ "$TERM" = 'xterm' ] && TERM=xterm-256color [ "$TERM" = 'screen' ] && TERM=screen-256color [ "$TERM" = 'rxvt-unicode' ] && TERM=rxvt-unicode-256color export TERM if [ ! -z "$TERMCAP" ] && [ "$TERM" = "screen-256color" ]; then TERMCAP=$(echo $TERMCAP | sed -e 's/Co#8/Co#256/g') export TERMCAP fi
As an optional additional improvement, we could adjust the 256 color values used in ls by editing the /etc/DIR_COLORS.256color file in the coreutils package, as it doesn't take as much advantage of the color range as it could.
As the default vim color scheme has some issues in 256 colors, we should also provide updates on this. Search, SpellLocal, ColorColumn and MatchParen are hardly readable (see :hi under vim). We should also avoid uses of bold attribute in vim highlighting as it can look bad especially at smaller font sizes. There are only a couple of uses of bold in the 256 color scheme so they can be easily avoided. Bold should be left in the vim 8 color scheme due to the effective doubling of colors that provides.
How To Test
Test as many colored terminal apps as possible under as many terminals as possible. Ensure screen works as expected too. There are screen testing notes at: http://www.robmeerman.co.uk/unix/256colours
To get the color numbers of your actual TERM, use the following:
$ tput colors 256
For testing any ls color changes you can use this command:
eval $(dircolors /etc/DIR_COLORS.256color) echo $LS_COLORS | tr : '\n' | sed 's/\(.*\)=\(.*\)/\x1b[\2m\1\t\2\x1b[0m/'
Better default colors with less tweaking required.
None necessary, revert to previous release behaviour
- The linux terminal (i.e. those on virtual consoles) doesn't support 256 colors and will break if applications send 256 color codes to it. This is handled in the config file above.
- Local xterms support this feature fine, though once you connect to other systems with SSH (which propagates the TERM environment variable), they will have to support the $TERM, or otherwise you will have a degraded experience. Debian for example traditionally didn't support xterm-256color unless the ncurses-term package was installed. Note ubuntu 12.04 at least does support xterm-256color so this is improving. Also as noted above Mac OS X 10.7 defaults to xterm-256color and so they're paving the way somewhat in this regard, so there should be less issues in connecting to older systems going forward.
Probably worth mentioning the case where users may need to reset their TERM to 'xterm' etc. when sshing to older systems. This issue is well known and similar to where you need to reset TERM on some systems when using the rxvt-unicode terminal for example. Something simple like this should suffice:
If you receive "unknown" or "not fully functional" terminal status messages when using remote systems over ssh, when you didn't before, then reset the TERM environment variable to 'xterm' for the remote system.