Bourne shell "if" syntax

[dteske at freebsd.org]

> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org [mailto:owner-freebsd-
> questions at freebsd.org] On Behalf Of lconrad at go2france.com
> Sent: Monday, June 10, 2013 11:53 AM
> To: freebsd-questions at freebsd.org
> Subject: Bourne shell "if" syntax
> 
> 
> 
> script fragment:
> 
> PTR=`dig @some.dns +short +norec -x a.b.c.d`
> 
> echo "$PTR"
> 
> if  [  "$PTR"  ==  ""  ]  ;  then
> 

if [ "$PTR" = "" ]; then

or

if [ -z "$PTR" ]; then

or

if [ "$PTR" ]; then

but _NOT_

if [ "$PTR" == "" ]; then

-- 
Devin


> echo "$PTR" >> /path/to/PTR_absent.txt
> 
> fi
> 
> ===========
> 
> output for an IP:
> 
> 
> a-b-c-d.domain.net.
> [: a-b-c-d.domain.net.: unexpected operator
> 
> thanks
> Len
> 
> 
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