Count network interfaces in Bash

It is possible using either a combination of grep and wc, or using awk

First approach, using grep:

ifconfig | grep "^tun" | wc -l

This will pipe the output of ifconfig through grep, match all lines starting with the string tun (this is accomplished using the "anchor" indicator ^), and then use wc to count the lines which grep output as matched.

As pointed out by @schaiba, it is even possible without resorting to wc by virtue of grep's -c option, which will count all matched lines by itself:

ifconfig | grep -c "^tun"

Second approach, using awk:

ifconfig | awk 'BEGIN {tuns=0}; /^tun/ {tuns++}; END {print tuns}'

This will pipe the output to awk. The awk program, enclosed between single quotes ' ... ', does the following:

• at the beginning (BEGIN { ... }), initialize an internal varible tuns, which we will use for book-keeping, as 0
• in the main loop, for every line encountered that starts with the string tun (indicated by the regular expression /^tun/), increase the counter tuns
• after the input is finished, (END { ... }), output the resulting value of tuns

You probably don't need ifconfig (or ip) for this. The interfaces are listed in /sys/class/net:

% ls /sys/class/net
eth0  lo  tun0  tun1  tun2  wlan0

So, you can count the directories there, with something like:

$ printf "%s\n" /sys/class/net/tun* | wc -l
3