How can I programmatically (in a shell script) determine whether or not there are changes?

Question

I am trying to create a Bash script that knows if there are changes in current working directory. I know that

$ git status

returns a messag

Answer 1

The git-diff man page describes two options of relevance here:

--quiet
Disable all output of the program. Implies --exit-code.

and

--exit-code
Make the program exit with codes similar to diff(1). That is, it
exits with 1 if there were differences and 0 means no differences.

Therefore, a robust approach would be to run

git diff --quiet; nochanges=$?

The shell variable nochanges will be equal to 0 (i.e. true) if there are no changes, and 1 (i.e. false) otherwise.

You can then use the value of nochanges in conditional statements as follows:

if [ $nochanges -eq 0 ]; then
    # there are no changes
else
    # there are changes
fi

Alternatively, if you don't need to store the exit status in a variable, you can do:

if git diff --quiet; then
    # there are no changes
else
    # there are changes
fi

---

Edit: Since git diff is a porcelain Git command and you want to do things programmatically, you should probably use the plumbing Git command called git diff-index instead (which also has a --quiet flag, but which must be supplied a tree-ish argument):

if git diff-index --quiet HEAD; then
    # there are no changes
else
    # there are changes
fi