I'm writing a BASH script. From the command line I can call nmap and I want to extract the ip for a specific port.

```
$ nmap [ip]/24

Starting Nmap 6.47 ( http://nmap.org ) at 2015-02-26 01:59 PST
Nmap scan report for 192.168.56.1
Host is up (0.0012s latency).
Not shown: 500 closed ports, 499 filtered ports
PORT     STATE SERVICE
3689/tcp open  rendezvous

Nmap scan report for 192.168.56.101
Host is up (0.00042s latency).
Not shown: 998 closed ports
PORT   STATE SERVICE
21/tcp open  ftp
22/tcp open  ssh

```

I want the IP address for the port 21. In this example that would be 192.168.56.101. How do I extract that from this return and save it to a variable? Thanks