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Accepted
User4283
Asked: 2010-10-09 08:10:54 +0800 CST

bash script help

  • 772

I'm using following script to dig a domain on multiple servers. But if a domain does not exist then also the output is "Resolved by server: domain.com ;". It just because the execution of the command returns 0 . Can any one help me if there are not records this should inform correct statement instead of printing wrong statement.

#!/bin/bash

a=$1
go="8.8.8.8"
f2="4.2.2.2"


if [ "$a" = "" ]
        then
echo "Usage: `basename $0` domain.com"
exit 1
        else

dig @"$go" "$a" +short
if  [ "$?" != 0 ]
        then
        echo "Server: $go did not resolve: $a ; "
        else
        echo "Resolved by $go: $a ; "
        echo " "
fi
        fi

if [[ -z $(dig @"$go" "$a" +short) ]] worked for me thanks :)

bash

2 Answers

  1. dig is a tool to check for problems on a DNS server, since a NXDOMAIN is not a problem it will return 0.
    dig will throw other codes e.g. when the server is down, the query is refused...

    Switch to a different tool like host:

    $ host serverfault.com 8.8.8.8 >/dev/null
$ echo $?
0
$ host serverfaultxyz.com 8.8.8.8 >/dev/null
$ echo $?
1
    • 1
  2. Best Answer

    Instead of:

    dig @"$go" "$a" +short
if  [ "$?" != 0 ]

    try:

    if [[ -z $(dig @"$go" "$a" +short) ]]
    • 0