threads / discuss / 56668

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

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

## tl;dr

6 messages between Oct 8, 2021 and Oct 8, 2021.

replies: 5people: 4as markdown or json

Alan Mackenzie· Oct 8, 2021, 17:51 UTC · lore

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!

-- 
Alan Mackenzie (Nuremberg, Germany).

Konstantin Ryabitsev· Oct 8, 2021, 18:01 UTC · re: Alan Mackenzie · lore

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

On Fri, Oct 08, 2021 at 05:51:17PM +0000, Alan Mackenzie wrote:

Show 7 quoted lines

> 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.

git show bar-branch:foo.c

-K

Alan Mackenzie· Oct 8, 2021, 18:15 UTC · re: Konstantin Ryabitsev · lore

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

Hello, Konstantin.

On Fri, Oct 08, 2021 at 14:01:23 -0400, Konstantin Ryabitsev wrote:

Show 8 quoted lines

> On Fri, Oct 08, 2021 at 05:51:17PM +0000, Alan Mackenzie wrote:
> > 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.

> git show bar-branch:foo.c

Thank you indeed.  That works just right!

> -K

-- 
Alan Mackenzie (Nuremberg, Germany).

Jeff King· Oct 8, 2021, 20:02 UTC · re: Alan Mackenzie · lore

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

On Fri, Oct 08, 2021 at 05:51:17PM +0000, Alan Mackenzie wrote:

Show 7 quoted lines

> 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.

Konstantin pointed you at git-show, which is what I would have used. But I just wanted to mention that you were on the right track. The invocation you wanted was:

  git cat-file blob bar-branch:foo.c

or:

  git cat-file -p bar-branch:foo.c

(the "-p" is "pretty-print based on the object's type", so the two are equivalent).

> Where might I have found this information for myself?

You found the cat-file manpage, which I agree is a bit thick. An Examples section would probably help a lot.

The other thing that might have helped is the gitrevisions(7) page, especially the <rev>:<path> entry. Your example above to use "<revs> -- <pathspec>" was a good thought, but the path there is for limiting diffs and traversals. What you want here is to specify the name of a single object, and gitrevisions gives all the ways to do that.

-Peff

Junio C Hamano· Oct 8, 2021, 21:54 UTC · re: Jeff King · lore

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

Jeff King <peff@peff.net> writes:

>   git cat-file -p bar-branch:foo.c
>
> (the "-p" is "pretty-print based on the object's type", so the two are
> equivalent).

IIRC, "cat-file -p" doesn't do textconv, but "show" would, and depending on the use case the difference may matter.

Jeff King· Oct 8, 2021, 23:01 UTC · re: Junio C Hamano · lore

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

On Fri, Oct 08, 2021 at 02:54:51PM -0700, Junio C Hamano wrote:

Show 9 quoted lines

> Jeff King <peff@peff.net> writes:
> 
> >   git cat-file -p bar-branch:foo.c
> >
> > (the "-p" is "pretty-print based on the object's type", so the two are
> > equivalent).
> 
> IIRC, "cat-file -p" doesn't do textconv, but "show" would, and
> depending on the use case the difference may matter.

Sorry, I should have been more clear. I meant that the two cat-file invocations are equivalent (using "blob" versus "-p").

I agree that for human consumption, "show" is preferable.

-Peff