[U-Boot] [PATCH] cmd_nvedit.c: Add env exists command
Andrew Ruder
andy at aeruder.net
Wed Oct 23 16:30:58 CEST 2013
On Wed, Oct 23, 2013 at 06:55:02AM -0700, James Chargin wrote:
> I have, more recently, been using scripting of the form
>
> if test "X" != "X${var}"; then
> echo defined
> else
> echo undefined
> fi
Thanks for the feedback.
I was attempting to do something like that originally but was hitting
problems related to the expansion which I'm still tracking down:
WRONG:
$ set var
$ test "x${var}" = "x" && echo undefined
undefined
$ set var 1
$ test "x${var}" = "x" && echo undefined
$ set var "1; 2; 3"
$ test "x${var}" = "x" && echo undefined
>> undefined
It DOES seem to work a lot better with != as you mentioned above
though...
RIGHT:
$ set var
$ test "x${var}" != "x" && echo defined
$ set var 1
$ test "x${var}" != "x" && echo defined
defined
$ set var "1; 2; 3"
$ test "x${var}" != "x" && echo defined
defined
- Andy
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