Prompt doesn't update git branch

Question

I tried to integrate the current git branch in my prompt, but it doesn't behave as expected. I'm using bash on ubuntu 16.04 and git 2.7.4. When I start a terminal nothing of git is shown. If I source my .bashrc from inside a repository the branch is shown, but doesn't update anymore. This is what I wrote in my .bashrc:

green="\[\033[01;32m\]"
blue="\[\033[01;34m\]"
no_color="\[\033[00m\]"
purple="\[\033[01;35m\]"

source ~/.git-prompt.sh
export PS1="$purple\u $green$(__git_ps1 " (%s)") $blue\W $no_color \$ "

Update:

I tried follow the instructions in git-prompt but still the same result. However if I just copy the suggestion from git-prompt: PS1='[\u@\h \W$(__git_ps1 " (%s)")]\$ ' it works, but of course doesn't look like I want. Is there some syntax error I'm missing? The template PS1 works even if don't use export, just PS1=...

Answer 1

Ok I found the solution. It is not necessary to use prompt command. The bug arises due to a syntax error.

If I assign the content of PS1 with "" in order to use my variables for the colors, it only executes the __git_ps1 function when .bashrc is sourced.

But when I assign the PS1 content within '' and do it without variables for the color and instead write the codes out, it works as expected. And as I read here it seems to be better practice not to export PS1 to the environment.

So the solution looks like:

PS1='\[\033[01;35m\]\u \[\033[01;32m\]$(__git_ps1 " (%s)") \[\033[01;34m\]\W \[\033[00m\] \$ '

However I would be curious to know, what's the reason for this. It works within "" in macOS.

Answer 2

Ran into the same problem. You can simply escape the $(...) to \$(...)

export PS1="$purple\u $green\$(__git_ps1 " (%s)") $blue\W $no_color \$ "

Answer 3

That's because .bashrc is read only once: when you start a new interactive non-login shell (when you open a new terminal, for example). So the PS1 is set the first time you open the terminal and is never changed.

The right way of doing this (assuming your git-prompt and __git_ps scripts work as expected) is to use PROMPT_COMMAND. As explained in man bash:

   PROMPT_COMMAND
          If set, the value is executed as a command prior to issuing each
          primary prompt.

You want __git_ps1 to be run before each prompt is shown (so after every command you run; after a cd, for instance). Therefore, you need to put it into PROMPT_COMMAND. If your __git_ps1 is what I think it is, it will be setting PS1 for you. You just need to run it each time a prompt is shown. So, add this line to your ~/.bashrc:

PROMPT_COMMAND="$purple\u $green$(__git_ps1 "(%s)") $blue\W $no_color \$ "

Finally, I can't be sure since you're not showing the relevant scripts, but I very much doubt that the (%s) makes sense there. That will just print the string %s. If you need more help, please edit your question and i) include both __git_ps1 and /etc/bash_completion.d/git-prompt (or tell us how you installed them if they came from an Ubuntu package) and ii) show us what your prompt is supposed to look like.