How to get the name of the current git branch into a variable in a shell script? [duplicate]

Question

I am new to shell scripting and can't figure this out. If you are unfamiliar, the command git branch returns something like

* develop   master 

, where the asterisk marks the currently checked out branch. When I run the following in the terminal:

git branch | grep "*" 

I get:

* develop 

as expected.

However, when I run

test=$(git branch | grep "*") 

or

test=`git branch | grep "*"` 

And then

echo $test 

, the result is just a list of files in the directory. How do we make the value of test="* develop"?

Then the next step (once we get "* develop" into a variable called test), is to get the substring. Would that just be the following?

currentBranch=${test:2}  

I was playing around with that substring function and I got "bad substitution" errors a lot and don't know why.

Answer 1

The * is expanded, what you can do is use sed instead of grep and get the name of the branch immediately:

branch=$(git branch | sed -n -e 's/^\* \(.*\)/\1/p') 

And a version using git symbolic-ref, as suggested by Noufal Ibrahim

branch=$(git symbolic-ref HEAD | sed -e 's,.*/\(.*\),\1,') 

To elaborate on the expansion, (as marco already did,) the expansion happens in the echo, when you do echo $test with $test containing * master then the * is expanded according to the normal expansion rules. To suppress this one would have to quote the variable, as shown by marco: echo "$test". Alternatively, if you get rid of the asterisk before you echo it, all will be fine, e.g. echo ${test:2} will just echo master. Alternatively you could assign it anew as you already proposed:

branch=${test:2} echo $branch 

This will echo master, like you wanted.

Answer 2

Expanding on Noufal Ibrahim's answer, use the --short flag with git-symbolic-ref, no need to fuss with sed.

I've been using something like this in hooks and it works well:

#!/bin/bash  branch=$(git symbolic-ref --short HEAD)  echo echo "**** Running post-commit hook from branch $branch" echo 

That outputs "**** Running post-commit hook from branch master"

Note that git-symbolic-ref only works if you're in a repository. Luckily .git/HEAD, as a leftover from Git's early days, contains the same symbolic ref. If you want to get the active branch of several git repositories, without traversing directories, you could use a bash one-liner like this:

for repo in */.git; do branch=$(cat $repo/HEAD); echo ${repo%/.git} :  ${branch##*/}; done 

Which outputs something like:

repo1 : master   repo2 : dev   repo3 : issue12 

If you want to go further, the full ref contained in .git/HEAD is also a relative path to a file containing the SHA-1 hash of the branch's last commit.