Re: [PATCH 2/2] t9200: avoid grep on non-ASCII data

From: Jeff King <peff@peff.net>
Date: Feb 22, 2016, 22:25 UTC
Message-ID: <20160222222503.GD18522@sigill.intra.peff.net>
In-Reply-To: <20160221234345.GB14382@river.lan>

On Sun, Feb 21, 2016 at 11:43:45PM +0000, John Keeping wrote:

Show 26 quoted lines

> On Sun, Feb 21, 2016 at 04:15:31PM -0500, Eric Sunshine wrote:
> > On Sun, Feb 21, 2016 at 12:32 PM, John Keeping <john@keeping.me.uk> wrote:
> > > GNU grep 2.23 detects the input used in this test as binary data so it
> > > does not work for extracting lines from a file.  We could add the "-a"
> > > option to force grep to treat the input as text, but not all
> > > implementations support that.  Instead, use sed to extract the desired
> > > lines since it will always treat its input as text.
> > >
> > > Signed-off-by: John Keeping <john@keeping.me.uk>
> > > ---
> > > diff --git a/t/t9200-git-cvsexportcommit.sh b/t/t9200-git-cvsexportcommit.sh
> > > @@ -35,7 +35,7 @@ exit 1
> > >  check_entries () {
> > >         # $1 == directory, $2 == expected
> > > -       grep '^/' "$1/CVS/Entries" | sort | cut -d/ -f2,3,5 >actual
> > > +       sed -ne '\!^/!p' "$1/CVS/Entries" | sort | cut -d/ -f2,3,5 >actual
> > 
> > This works with BSD sed, but double negatives are confusing. Have you
> > considered this instead?
> > 
> >     sed -ne '/^\//p' ...
> 
> What do you mean double negatives?  Do you mean using "!" as an
> alternative delimiter?  I find changing delimters is normally simpler
> than following multiple levels of quoting for escaping slashes, although
> in this case it's simple enough that it doesn't make much difference.

I agree that changing delimiters is much nicer than backslashes. But I wonder if using "!" is more confusing than it needs to be, given its other meanings.

I dunno. I admit that the backslash threw me off, too (since it needs escaped in interactive shells, I first assumed that's what was going on). Using backslash to select the delimiter was new to me. I've usually seen:

  s!/foo/!/bar/!

which is arguably a little more clear. Too bad we cannot do:

  m!/foo!

which I think reads better. Oh well. Maybe:

  sed -ne '\#^/#p'

would be more readable, but I'm just bikeshedding at this point. The grep invocation really was the most clear. :-/

-Peff