When I need to know whether a particular interface exists  – and, if so, what IP address and MTU it has – my script is inevitably bulky. I then bombard the results of ip addr show eth0, ifconfig, or iwconfig with grep, cut, and regular expressions until the requested information is chiseled out. In contrast, ifdata from the Moreutils package [1] solves my task elegantly. I can use parameters to control the ifdata output so that only the desired result appears, which is ideal for ongoing processing in a script. If I want to know whether a specific network interface exists, I can use:

ifdata -e eth0

The command produces no output, but the return value reveals whether the interface exists. In a script, this is very convenient if I want to branch:

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