Andrew (he/him)You may have seen some cool zsh prompts that show the name of the current Git branch in the prompt, like this one from oh-my-zsh:
I wanted to recreate something like that in bash and discovered that it's actually really easy to generate a dynamic bash prompt. Let's start with a boring old static prompt:
$ export PS1="\n$ "
$ ls
Applications Documents Dropbox Library
Desktop Downloads Git Movies
$
This sets my prompt to just a $ sign, with a newline before it so the output of the previous command isn't directly adjacent to the next prompt. To add a function to a bash prompt, all we need to do is include it as a subshell within the definition of PS1, making sure to escape the $ at the beginning of the subshell syntax, like so:
$ export PS1="\n\$(date)\n$ "
Thu 25 Jul 2019 14:27:23 IST
$ ls
Applications Documents Dropbox Library
Desktop Downloads Git Movies
Thu 25 Jul 2019 14:27:25 IST
$
Now, to check what branch we're on in a git project, we can do
Thu 25 Jul 2019 14:32:12 IST
$ git status
On branch my-test-branch
Your branch is up to date with 'origin/my-test-branch'.
nothing to commit, working tree clean
This gives us the current branch name in the first line. We can select that line with grep and parse it with sed:
Thu 25 Jul 2019 14:34:45 IST
$ git status | grep 'On branch' | sed 's/On branch / => /'
=> my-test-branch
But what happens if we're not within a git repo?
Thu 25 Jul 2019 14:35:06 IST
$ cd
Thu 25 Jul 2019 14:35:12 IST
$ git status | grep 'On branch' | sed 's/On branch / => /'
fatal: not a git repository (or any of the parent directories): .git
Oof, error text. Let's redirect all error output to /dev/null:
Thu 25 Jul 2019 14:35:26 IST
$ git status 2>/dev/null | grep 'On branch' | sed 's/On branch / => /'
There's now no output at all when the current directory isn't a git repo, so grep returns nothing and so does sed. Finally, let's add this to the prompt:
Thu 25 Jul 2019 14:35:36 IST
$ export PS1="\n\$(date)\$(git status 2>/dev/null | grep 'On branch' | sed 's/On branch / => /')\n$ "
Thu 25 Jul 2019 14:35:41 IST
$ cd Git/my_git_project/
Thu 25 Jul 2019 14:35:49 IST => my-test-branch
$ git checkout master
Switched to branch 'master'
Your branch is up to date with 'origin/master'.
Thu 25 Jul 2019 14:35:53 IST => master
$
That's it! You now have the same functionality as those fancy styled shells that display your current git branch. Just add some colour to this and you're good to go.
