On Tue, Feb 26, 2019 at 04:01:01PM -0500, Jeff King wrote:
> > + { set +x ; } 2>/dev/null 4>/dev/null
>
> Ah, this is the magic. Doing:
>
> set +x 2>/dev/null
>
> will still show it, but doing the redirection in a wrapping block means
> that it is applied before the command inside the block is run. Clever.
Yeah, clever, but unfortunately (and to me suprisingly) unportable:
$ ksh
$ set -x
$ echo foo
+ echo foo
foo
$ set +x
$
It doesn't show 'set +x', how convenient! :)
However:
$ set -x
$ echo foo 2>/dev/null
+ echo foo
+ 2> /dev/null
foo
$ { set +x; } 2>/dev/null
+ 2> /dev/null
$
Apparently ksh, ksh93 and mksh show not only the executed commands
but any redirections as well. It's already visible when running our
tests with ksh and '-x':
$ ksh ./t9999-test.sh -x
Initialized empty Git repository in /home/szeder/src/git/t/trash
directory.t9999-test/.git/
expecting success:
true
+ true
+ 2> /dev/null ok 1 - first
# passed all 1 test(s)
1..1
NetBSD's sh:
# set -x
# echo foo
+ echo foo
foo
# echo foo 2>/dev/null
+ echo foo 2>/dev/null
foo
# { set +x; } 2>/dev/null
+ using redirections: 2>/dev/null do
