bash - sh variable not working if blank -

need eyes one...

dns_lookup() {     ip_set     if [ `ip_ping ${ip_address}` -eq 0 ]                 host=""             dig +short -x ${ip_address} | sed 's/\.$//g' | while read host                                 if [ -z "${host}" ]                                                 host="unknown"                     fi                     echo "${ip_address},${host}"             done     fi 

}

i desired results if ip pingable , has dns name. not results if ip pingable not have dns name.

---

ip_set() {         ip_address="${a}.${b}.${c}.${d}" }  ip_ping() {   timeout ${delay} ping -q -c 1 -i 1 -w 1 -w 4 $1 > /dev/null 2>&1 ; echo $? } 

---

perhaps need. tell me if need revisions.

dns_lookup() {     ip_set     if [ `ip_ping ${ip_address}` -eq 0 ]             host=""         dig +short -x ${ip_address} | sed 's/\.$//g' | {             hashosts=false             while read host                             if [ -n "${host}" ]                                     hashosts=true                     echo "${ip_address},${host}"                 fi             done             [ "${hashosts}" = false ] && echo "${ip_address},unknown"         }     fi } 

i have suggested change of function ip_ping that_other_guy did it.