mno len problem je v tom, ze nslookup ani dig nemaju ziadne navratove hodnoty teda:

funkcne
# dig www.google.sk
; <<>> DiG 9.5.1-P1 <<>> www.google.sk
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47892
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 7, ADDITIONAL: 0
.
;; AUTHORITY SECTION:
l.google.com. 79884 IN NS e.l.google.com.
.
.
# echo $?
0

nefunkcne
# dig sdfa

;; <<>> DiG 9.5.1-P1 <<>> sdfa
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 38970
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
; <<>> DiG 9.5.1-P1 <<>> sdfa
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 38970
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
.
.

# echo $?
0

a ked pouzijem dig tak neviem grepovat nic co by mi jednoznacne identifikovalo ze nic nenaslo ako u nslookup:
** server can't find www.google.: NXDOMAIN

resp. neviem ako to spravit :) Povodne som mal vacsie "monitorovacie" plany s nagiosom ale ked som kolko je to prace tak som to "odlozil" na neskor ))