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Are there any tools baked in to linux that I can use to validate the syntax in /etc/network/interfaces or /etc/network/interfaces/*.conf files akin to the way I can validate sudo using visudo before installing it.

I'm writing scripts to be deployed in the old "internet-of-things-that-aught-to-be-set-up-right-in-the-first-place-but-most-likely-aren't" methodology and want to unit test my config generators.

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You can use the command ifup --no-act --interfaces=/home/user/interfaces.new eth0 to check for syntax errors in a specified interface file on an interface that is already up.

If errors exist you will get a message stating the incorrect line number and something about being unable to parse the interface file.

If there are no errors, then you will get a message stating that the interface is already configured.

You can check the return value of the command by looking at the value of the $? variable after running the command in your script.

Look at man ifup for more information.

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    ifup has to read from interfaces it can see, not an arbitrary location. So if I have to re-configure an interface, backing up the interface config, running that ifup --no-act copying in my new one and restoring it if there are shell errors is the way to go. It's a little risky, but oh well. Doing it in python so I should be able to catch exceptions easy enough. – Peter Turner Dec 10 '15 at 21:31
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    ifup --no-act --interfaces=/home/user/interfaces.new eth0 – ewatt Dec 10 '15 at 21:47

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