From: Jeff King <peff@peff.net>
Date: Wed, 01 Jun 2016 03:54:08 GMT
Subject: Re: [PATCH] t4014: shell portability fix
Message-ID: <20160601035408.GD5411@sigill.intra.peff.net>
In-Reply-To: <20160601034413.GC5411@sigill.intra.peff.net>

On Tue, May 31, 2016 at 11:44:13PM -0400, Jeff King wrote:

> # probably not portable; also, possible without sub-program?
> is_exported () {
> 	export -p | grep "^declare -x $1="
> }

Obviously this should have been "grep -q" (and my test didn't notice
because the variable isn't actually exported!).

But yeah, this is not very portable. Doing:

  export AAAA=content
  for i in bash dash mksh ksh93
  do
    printf '%5s ==> ' $i
    $i -c 'export -p' | head -1
  done

yields:

   bash ==> declare -x AAAA="content"
   dash ==> export AAAA='content'
   mksh ==> export AAAA=content
  ksh93 ==> export AAAA=content

which is actually not too hard to pattern-match, but who knows what else
exists. I guess another strategy would be to actually spawn a
sub-process and see if it has the variable set.

I think my code also doesn't handle exported-but-unset variables, though
I'm not sure we really need to care about that in practice.

-Peff