Ubuntu – Why is the function not re-evaluated in PS1

bashbashrccommand linepromptps1

I'm trying to have a part of my prompt set dynamically by a function, so in my .bashrc I have:

asdf ()
{
    echo -n $(pwd)
}
PS1="\u@\h:\w $(asdf)\$ "

Opening a shell gives me what I expect at first:

$ bash
darthbith@server:~/test /home/darthbith/test$

However, when I change directory, the part defined by the function doesn't change:

darthbith@server:~/test /home/darthbith/test$ cd ~/test2
darthbith@server:~/test2 /home/darthbith/test$

My actual goal is to use the git-prompt.sh script to show the branch of my git repository when I'm in one with pretty colors and everything, but the problem is that it never updates the branch name when I change repositories. The trivial example above is the simplest reproduction I could come up with for my question.

The .bashrc lines that I have to integrate the git-prompt script:

source ~/.git-prompt.sh
PS1="\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]$(__git_ps1)\$ "

Best Answer

  • According to Bash prompt Howto:

    [21:58:33][giles@nikola:~]$ PS1="[\$(date +%H%M)][\u@\h:\w]\$ "
    [2159][giles@nikola:~]$ ls
    bin   mail
    [2200][giles@nikola:~]$
    

    It's important to notice the backslash before the dollar sign of the command substitution. Without it, the external command is executed exactly once: when the PS1 string is read into the environment.