get ip address with script

#!/bin/bash

get_ip()    
{
    ip=$(ifconfig wlan0 | awk '/inet addr/{print substr($2,6)}')
    if [ ! $ip ]; then
      echo "IS NULL"
      sudo a02-wifi-connect 1 aa wpa bb    
    else
      echo "NOT NULL, a=$a"
    fi  
}

get_ip

ref: stackexchange