How to set different shell prompt color for each newly opened terminal

Question

I am using Ubuntu and can manually change the bash shell prompt color to green using

export PS1="\e[0;32m[\u@\h \W]\$ \e[m"

However, I want the shell prompt color to automatically change whenever I open a new terminal or tab. I am aware that the basic tty TERM has 16 colors, and it's okay to rotate the colors if more than 16 terminals are open. Will the solution also work when I connect through Putty, tmux or screen.

My idea is to write a shell script and place it in .bashrc which detects the new terminal session the user has opened and increment a global counter from \e[0;31m[ to \e[0;47m[. How to detect the number of opened terminals by the user?

Answer 1

Counting the terminals (ex: who - a | grep user | wc -l ) will not work : when one or seceral shell are closed, the total number decreases and the new terminal may match another one already opened.

You should simply have a counter:

If you want 6 colors overall:

touch ~/.colornumber
new=$(awk '(NR==1) { print ($1 + 1) % 6; }' ~/.colornumber)
echo $new > ~/.colornumber
#and use color number $new for your current terminal, for example defined in an array of 6 entries. 
 # just note here that color 0 is for the 6th terminal, not the first... or change the awk above