The logic desired if
If IP has no PTR, print "PTR_NUL", else print the PTR.
dig +short -x 1.2.3.4 | awk '{if ( $0 == "" ) {print "PTR_NUL" } else {print $0 } }'
... works if PTR exist, but if no PTR, PTR_NUL doesn't print.
thanks
Len
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