Show sha1 only with git log

Question

I want to write a Bash script that loops over the sha1s of commits output by an invocation of git log. However, git log gives me much more output than I want:

commit 0375602ba2017ba8750a58e934b41153faee6fcb
Author: Mark Amery <[email protected]>
Date:   Wed Jan 1 21:35:07 2014 +0000

    Yet another commit message

    This one even has newlines.

commit 4390ee9f4428c84bdbeb2fed0a461099a6c81b39
Author: Mark Amery <[email protected]>
Date:   Wed Jan 1 21:30:19 2014 +0000

    Second commit message.

commit bff53bfbc56485c4c1007b0884bb1c0d61a1cf71
Author: Mark Amery <[email protected]>
Date:   Wed Jan 1 21:28:27 2014 +0000

    First commit message.

How can I get git log to just output sha1s so that I can loop over them conveniently?

Answer 1

You can use the --format argument with a custom format that only includes the sha1:

git log --format=format:%H

The above command yields output like the following:

0375602ba2017ba8750a58e934b41153faee6fcb
4390ee9f4428c84bdbeb2fed0a461099a6c81b39
bff53bfbc56485c4c1007b0884bb1c0d61a1cf71

You can loop over the commit hashes in Bash like this:

for sha1 in $(git log --format=format:%H); do
    : # Do something with $sha1
done

This is slightly more verbose than using git rev-list, but may be your only option if you want to use ordering or filtering arguments for git log that are not supported by git rev-list, like -S.