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my_ip=`cat /proc/net/arp | grep eth0 | awk '{ print $1 }'`

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case `cat /proc/net/arp | grep eth0 | awk '{ print $1 }'` in
  192.168.1.1)
    mount blah
    mount blub
  ;;
  192.168.1.2)
    mount foo
    mount bar
  ;;
  *)
    echo "Unknown ip address!"
    exit 1
esac