Shell Programming and Scripting

Allright so a quick question.

I'm building a script that will eventually do a full IP subnet scan.
It starts off by first entering an IP address, (capturing host and net ID comes after that) and I want it to use the current IP address if no input is given.

Is there a quick way to define the value of the variable I want to read when no value is given?

Now I've already figured out how to extract the IP address from ifconfig using:

Code:

CURRENTIP=$(ifconfig eth0 | grep 'inet addr' | cut -d: -f2 | awk '{print $1}')

echo "Which IP subnet?"
read TARGETSUBNET

So what's the quickest way to go about in giving TARGETSUBNET the value of CURRENTIP when no input is given for read?

Cheers,

Marc

you can use the getopts command in your shell script:

getopts -- parse options from shell script command line