Check for IP validity

Question

How do I check the validity of an IP address in a shell script, that is within the range 0.0.0.0 to 255.255.255.255?

Answer 1

You can just copy the following code and change body of if else control as per your need

function checkIP(){
echo "Checking IP Integrity"    
ip=$1
byte1=`echo "$ip"|xargs|cut -d "." -f1`
byte2=`echo "$ip"|xargs|cut -d "." -f2`
byte3=`echo "$ip"|xargs|cut -d "." -f3`
byte4=`echo "$ip"|xargs|cut -d "." -f4`


if [[  $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$  && $byte1 -ge 0 && $byte1 -le 255 && $byte2 -ge 0 && $byte2 -le 255 && $byte3 -ge 0 && $byte3 -le 255 && $byte4 -ge 0 && $byte4 -le 255 ]]
then
    echo "IP is correct"
else
    echo "This Doesn't look like a valid IP Address : $ip" 
fi
}
checkIP $myIP 

Calling the method with IP Address stored in a variable named myIP.

$ip =~ ^[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}$ - This part makes sure that IP consists of 4 blocks separated by a dot(.) but every block here is allowed to range from 0 - 999

Since desired range of every block would be 0 - 255, to make sure of that below line can be used.

$byte1 -ge 0 && $byte1 -le 255 && $byte2 -ge 0 && $byte2 -le 255 && $byte3 -ge 0 && $byte3 -le 255 && $byte4 -ge 0 && $byte4 -le 255