Re: [PATCH] filter-branch: use printf instead of echo -e

From: Jeff King <peff@peff.net>
Date: Mar 20, 2018, 04:22 UTC
Message-ID: <20180320042245.GA13302@sigill.intra.peff.net>
In-Reply-To: <20180319153945.kchupu43cpcbg25n@hashpling.org>

On Mon, Mar 19, 2018 at 03:39:46PM +0000, CB Bailey wrote:

Show 21 quoted lines

> > diff --git a/git-filter-branch.sh b/git-filter-branch.sh
> > index 1b7e4b2cd..21d84eff3 100755
> > --- a/git-filter-branch.sh
> > +++ b/git-filter-branch.sh
> > @@ -627,7 +627,7 @@ then
> >  				print H "$_:$f\n" or die;
> >  			}
> >  			close(H) or die;' || die "Unable to save state")
> > -	state_tree=$(/bin/echo -e "100644 blob $state_blob\tfilter.map" | git mktree)
> > +	state_tree=$(printf '100644 blob %s\tfilter.map\n' "$state_blob" | git mktree)
> >  	if test -n "$state_commit"
> >  	then
> >  		state_commit=$(/bin/echo "Sync" | git commit-tree "$state_tree" -p "$state_commit")
> 
> I think the change from 'echo -e' to printf is good because of the
> better portability reason that you cite.
> 
> Looking at the change, I am now curious as to why '/bin/echo' is used.
> Testing on a Mac, bash's built in 'echo' recognizes '-e' whereas
> '/bin/echo' does not. This is just an observation, I still prefer the
> move to 'printf' that you suggest.

Right. Moving them to just "echo -e" would work on systems where /bin/sh is bash, but not elsewhere (e.g., Debian systems with "dash" whose built-in echo doesn't understand "-e").

So my guess as to why /bin/echo was used is that on Linux systems it's _more_ predictable and portable, because you know you're always going to get the GNU coreutils version, which knows "-e". Even if you're using a non-bash shell.

But on non-Linux systems, who knows what system "echo" you'll get. :)

Author cc'd in case there's something more interesting going on.

-Peff