Date: 27 Apr 1997 06:12:36 +0100 From: Andrew Gierth <andrew@erlenstar.demon.co.uk> To: Curt Sampson <cjs@portal.ca> Cc: hackers@freebsd.org Subject: Re: /etc/netstart bogons.. Message-ID: <874tctkq0r.fsf@erlenstar.demon.co.uk> In-Reply-To: Curt Sampson's message of Sat, 26 Apr 1997 21:47:32 -0700 (PDT) References: <Pine.NEB.3.93.970426214717.24845C-100000@gnostic.cynic.net>
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>>>>> "Curt" == Curt Sampson <cjs@portal.ca> writes:
>> Can't let this slip past: "" and unset are certainly not the same in sh.
Curt> So how do we test for the difference between the two?
$ sh
$ if [ -z "${var+X}" ]; then echo "variable 'var' is not set"; fi
variable 'var' is not set
$ var=''
$ if [ -z "${var+X}" ]; then echo "variable 'var' is not set"; fi
$
Or, if you want "unset" to be treated like "NO", then
$ unset var
$ echo "value is '${var-NO}'"
value is 'NO'
$ var=''
$ echo "value is '${var-NO}'"
value is ''
$ var='foo'
$ echo "value is '${var-NO}'"
value is 'foo'
$
--
Andrew.
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