Is it possibly to copy certain text from a file

i have a script that will configure my wireless card $interface
and i would like it to grap the mac address of the $interface so i thought

ifconfig $interface > add.txt

but since it will say alot of things in there when i type ifconfig including the mac address is it possible just to get a certian part i.e. search a file for **:**:**:**:**:** then put it in a var called $mac

Thanks

Yes, you can build a regular expression to match the MAC address and use egrep -o to get the result, e.g something like
but more simply you can do something like
since the MAC address is the last field of the line containing "HWaddr".

do you mean the ip address?
here's what my 'ifconfig wlan0' displays:
ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 00:21:5d:b2:e5:96
inet addr:10.62.11.219 Bcast:10.62.11.223 Mask:255.255.255.224
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1630626 errors:0 dropped:0 overruns:0 frame:0
TX packets:1040182 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2140727532 (1.9 GiB) TX bytes:243190342 (231.9 MiB)

The IP address can be seen in the line with 'inet addr:...'

If I want to store the IP address into a variable, I'd go this
way:
1. make sure the interface is up (ifconfig wlan0 up)
2. make sure the IP address has been attributed
if [ $(ifconfig wlan0 | grep -c 'inet addr:') -eq 0 ]; then
#no ip address found
... exit the script ...
fi
3. the ip address exists, store it in the variable mac:
mac=$(ifconfig wlan0 | grep 'inet addr:' | sed 's?.*inet addr:\([0-9][.0-9]*\).*$?\1?')

4. check:
echo $mac
should display:
10.62.11.219

replace wlan0 by the name of your interface if it's different

colucix you my friend are a LEGEND