bash question - changing prompt colors based on pwd

[doctordruidphd]

What I want to accomplish is: changing the prompt color based on the directory I am using.

I have several OS versions installed, and for example, if I am cd's into another OS's directory structure, working on files there, I would like the prompt to be a different color than if I am in the home OS. All of the other OS's are accessed through /media -- /media/testing, /media/aptosid, etc., so a test that looks for "/media/" would work.

The idea here is that if I am changing files around, I can tell at a glance that I am doing it in the right place. So I don't, for example, change all of my source entries from "natty" to "oneiric" in my natty directory. You should be able to figure out from that example why I want to change the prompt colors...

The relevant /bashrc line is this:

if [ "$color_prompt" = yes ]; then
PS1='${debian_chroot:+($debian_chroot)}\[\033[00;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

but I'm not quite sure how to insert a test line in this, or even if it would work without reloading the shell.

[oshunluvr]

Re: bash question - changing prompt colors based on pwd

Look into dircolors and how to edit it. You might have to experiment but maybe it will let you enter

/media/test=1:31

or something similar.

[oshunluvr]

Re: bash question - changing prompt colors based on pwd

Sorry, that doesn't work. How about nested if's?

if [ "$color_prompt" = yes ]; then
if [ "$PWD"="/media/testing" ]; then
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u@\h\[\033[00m\]:\[\033[01;31m\]\w\[\033[00m\]\$ '
else
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
fi
else
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi

Still, it wouldn't take effect unless you reloaded bash right?

EDIT: Tested and it works if you open the konsole with the --workdir /media/testing option. However, it stays the same color when you change directories which isn't what you want I think.

[oshunluvr]

Re: bash question - changing prompt colors based on pwd

How about an alias for "cd /media/testing" that would change the prompt? But again, you'd have to be able to change it back automatically.

[doctordruidphd]

Re: bash question - changing prompt colors based on pwd

Thanks for your efforts and suggestions.

I expect that a script won't work, at least not one that is part of .bashrc, because, as I understand it, .bashrc is read only when the shell is invoked, so cd'ing once the shell is started would never get picked up. I tried something like that anyway, and it didn't work.

One could set up a script that is read every time a prompt is issued. I suspect the only way to really get it to work would be to hack dircolors, or something like that, so that it would recognize specific directories, and issue colors for them. I am going to try playing with LS_COLORS and see if I can get it to recognize directories.

[Guest]

I realise this questing is over 2 years old however it came up high on Google when I was looking to do the same thing. Anyway oshunluvr gave me the idea for this script:

https://gist.github.com/Gisleburt/c560f99d9e9ada359934

#!/bin/bash
 
if [[ $# -gt 0 ]]
then
        pushd "$1" >> /dev/null
fi
 
if [[ "$PWD" == *'/live/'* ]]
then
        # red
        PS1='\[\e[0;31m\]\u@\h:\w\$ \[\e[m\]';
elif [[ "$PWD" == *'/stage/'* ]]
then
        # green
        PS1='\[\e[0;32m\]\u@\h:\w\$ \[\e[m\]';
else
        # white
        PS1='\[\e[0;37m\]\u@\h:\w\$ \[\e[m\]';
fi

You can alias that to cd and it will do what you want.

[jlittle]

(I didn't see this the first time round.)

I think it's nicer to make the prompt colouring independent of the command or commands used to change directories. Bash can execute stuff while outputing the prompt, using the $() syntax. First, define a function, maybe in .bashrc, or a file sourced from it:

function cp
{
    case $PWD in 
        /media/Oneiric*)
            col=31;; # red
        /media/windows*)
            col=32;; # green
        /media/Mint*)
            col=36;; # cyan
        *)
            col=40;; # white
    esac
    echo -ne "\e[1;${col}m"
}

then include $(cp) in the setting of PS1:

PS1='\[$(cp)\]\u@\h:\w\$ \[\e[m\]';

I sometimes have lots of stuff in such a function, depending on the needs of the job, usually to trim the directory to the most relevant parts, to keep the prompt not too long.

Regards, John Little

[Guest]

I didn't realise you could have functions in PS1, that's a much more elegant solution.