How do I get the file contents from an arbitrary revision to stdout?

Hello, git.

I want to get a file's content from a particular revision onto stdout for backup purposes. I can't see how to do this. Help me, please!

Let's say the file is foo.c, and I want to get the version from the head revision of bar-branch.

I would like there to be a command something like:

    $ git cat bar-branch -- foo.c

.. Is there such a command, and if so, what's it called and how do I use it? I assumed it might be git cat-file, but I couldn't get it to work, and couldn't understand it's man page.

Where might I have found this information for myself?

Thanks in advance for the help!