Linux Shell Scripting Cookbook - Third Edition

Printing the list of network interfaces

This one-line command sequence displays network interfaces available on a system:

$ ifconfig | cut -c-10 | tr -d ' ' | tr -s 'n' 
lo 
wlan0 

The first ten characters of each line in ifconfig output is reserved for writing names of network interfaces. Hence, we use cut to extract the first ten characters of each line. tr -d ' ' deletes every space character in each line. Now, the n newline character is squeezed using tr -s 'n' to produce a list of interface names.