Re: unset FOO

[Eric Blake]

Peter Seebach <seebs <at> seebs.net> writes:

> 
> In regards to worries about "unset FOO" not working if FOO is not set:
> 
> ${FOO+unset FOO}
> 
> Is this crazy or clever?  It works in Solaris sh.  (I know, in most cases,
> it's sufficient to just empty the variable, but sometimes it'd be nice to
> be able to distinguish between empty and unset.)

No, it does NOT work in Solaris sh (tested on Solaris 8):

$ /bin/sh -c 'foo=a;${foo+unset foo};echo ${foo+set}' ; echo $?
/bin/sh: bad substitution
1

-- 
Eric Blake