How, then, can I set things up so that both dark- and light-backgrounded people can use the account? I could set up a script that would set up a different set of aliases and configuration files, like when I changed my vim colors. Better, I could fix all of them at once by changing my terminal's idea of colors -- so when the remote machine thinks it's feeding me a light color, I see a dark one.
I use xterm, which has an easy way of setting colors: it has a list of 16 colors defined in X resources. So I can change them in ~/.Xdefaults.
That's all very well. But first I needed a way of seeing the existing colors, so I knew what needed changing, and of testing my changes.
Script to show all terminal colors
I thought I remembered once seeing a program to display terminal colors, but now that I needed one, I couldn't find it. Surely it should be trivial to write. Just find the escape sequences and write a script to substitute 0 through 15, right?
Except finding the escape sequences turned out to be harder than I expected. Sure, I found them -- lots of them, pages that conflicted with each other, most giving sequences that didn't do anything visible in my xterm.
Eventually I used
script to capture output from a vim session
to see what it used. It used <ESC>[38;5;Nm to set color
N, and <ESC>[m to reset to the default color.
This more or less agreed Wikipedia's
escape code page, which says <ESC>[38;5; does "Set xterm-256
text coloor" with a note "Dubious - discuss". The discussion says this
isn't very standard. That page also mentions the simpler sequence
<ESC>[0;Nm to set the
first 8 colors.
Okay, so why not write a script that shows both? Like this:
#! /usr/bin/env python # Display the colors available in a terminal. print "16-color mode:" for color in range(0, 16) : for i in range(0, 3) : print "\033[0;%sm%02s\033[m" % (str(color + 30), str(color)), print # Programs like ls and vim use the first 16 colors of the 256-color palette. print "256-color mode:" for color in range(0, 256) : for i in range(0, 3) : print "\033[38;5;%sm%03s\033[m" % (str(color), str(color)), print
Voilà! That shows the 8 colors I needed to see what vim and ls were doing, plus a lovely rainbow of other possible colors in case I ever want to do any serious ASCII graphics in my terminal.
Changing the X resources
The next step was to change the X resources. I started by looking for where the current resources were set, and found them in /etc/X11/app-defaults/XTerm-color:
$ grep color /etc/X11/app-defaults/XTerm-color irrelevant stuff snipped *VT100*color0: black *VT100*color1: red3 *VT100*color2: green3 *VT100*color3: yellow3 *VT100*color4: blue2 *VT100*color5: magenta3 *VT100*color6: cyan3 *VT100*color7: gray90 *VT100*color8: gray50 *VT100*color9: red *VT100*color10: green *VT100*color11: yellow *VT100*color12: rgb:5c/5c/ff *VT100*color13: magenta *VT100*color14: cyan *VT100*color15: white ! Disclaimer: there are no standard colors used in terminal emulation. ! The choice for color4 and color12 is a tradeoff between contrast, depending ! on whether they are used for text or backgrounds. Note that either color4 or ! color12 would be used for text, while only color4 would be used for a ! Originally color4/color12 were set to the names blue3/blue !*VT100*color4: blue3 !*VT100*color12: blue !*VT100*color4: DodgerBlue1 !*VT100*color12: SteelBlue1
So all I needed to do was take the ones that don't show up well -- yellow, green and so forth -- and change them to colors that work better, choosing from the color names in /etc/X11/rgb.txt or my own RGB values. So I added lines like this to my ~/.Xdefaults:
!! color2 was green3 *VT100*color2: green4 !! color8 was gray50 *VT100*color8: gray30 !! color10 was green *VT100*color10: rgb:00/aa/00 !! color11 was yellow *VT100*color11: dark orange !! color14 was cyan *VT100*color14: dark cyan... and so on.
Now I can share accounts, and I no longer have to curse at those default ls and vim settings!
Update: Tip from Mikachu: ctlseqs.txt is an excellent reference on terminal control sequences.
[ 10:56 Jan 18, 2011 More linux | permalink to this entry | ]