Shell – Random colors and jokes in the shell/terminal

Here are a couple of things you can do:

Editors + Code
A lot of editors have syntax highlighting support. vim and emacs have it on by default. You can also enable it under nano.

You can also syntax highlight code on the terminal by using Pygments as a command-line tool.

grep
grep --color=auto highlights all matches. You can also use export GREP_OPTIONS='--color=auto' to make it persistent without an alias. If you use --color=always, it'll use colour even when piping, which confuses things.

ls

ls --color=always

Colors specified by:

export LS_COLORS='rs=0:di=01;34:ln=01;36:mh=00:pi=40;33'

(hint: dircolors can be helpful)

PS1
You can set your PS1 (shell prompt) to use colours. For example:

PS1='\e[33;1m\u@\h: \e[31m\W\e[0m\$ '

Will produce a PS1 like:

[yellow]lucas@ubuntu: [red]~[normal]$

You can get really creative with this. As an idea:

PS1='\e[s\e[0;0H\e[1;33m\h    \t\n\e[1;32mThis is my computer\e[u[\u@\h:  \w]\$ '

Puts a bar at the top of your terminal with some random info. (For best results, also use alias clear="echo -e '\e[2J\n\n'".)

Getting Rid of Escape Sequences

If something is stuck outputting colour when you don't want it to, I use this sed line to strip the escape sequences:

sed "s/\[^[[0-9;]*[a-zA-Z]//gi"

If you want a more authentic experience, you can also get rid of lines starting with \e[8m, which instructs the terminal to hide the text. (Not widely supported.)

sed "s/^\[^[8m.*$//gi"

Also note that those ^[s should be actual, literal ^[s. You can type them by pressing ^V^[ in bash, that is Ctrl + V, Ctrl + [.

Colors in terminals are determined in two steps:

• the program running in the terminal tells the terminal to use a certain color number;
• the terminal translates each color number into a color value.

Xterm has an escape sequence to change the color value associated with a color number. I don't remember whether PuTTY supports this sequence; I know Mintty does.

set_color_value () {
  printf "\\e]4;$1;$2\\a"
}
set_color_value 4 '#6495ed'  # set color 4 (blue) to CornflowerBlue

These settings won't survive a terminal reset. You can overcome this difficulty by appending the cursor configuration changing sequence to your terminal's reset string.

• On a terminfo-based system using ncurses, save your terminal's terminfo settings to a file with infocmp >>~/etc/terminfo.txt. Edit the description to change the rs1 (basic reset) sequence, e.g. replace rs1=\Ec by rs1=\Ec\E]4;4;#6495ed\E\\. With some programs and settings, you may need to change the rs2 (full reset) as well. Then compile the terminfo description with tic ~/etc/terminfo.txt (this writes under the directory $TERMINFO, or ~/.terminfo if unset).
• On a termcap-based system, grab the termcap settings from your termcap database (typically /etc/termcap). Change the is (basic reset) and rs (full reset) sequences to append your settings, e.g. :is=\Ec\Ec\E]4;4;#6495ed\E\\:. Set the TERMCAP environment variable to the edited value (beginning and ending with :).

Now you can put something like this in your ~/.profile:

if [ "$(ps -p $PPID -o comm=)" = sshd ] &&
   [ "$TERM" = "xterm" ]; then
  set_color_value … # set color scheme
  TERMCAP=…  # if necessary
fi