readFileSync Appears Un-synchronous or Fails on Raspberry Pi 3

[noncreature0714]

• Version: v6.9.3
• Platform: Linux raspi-pi3-woody 4.4.38-v7+ build: make test-ci output TAP to stdout and log #938 SMP Thu Dec 15 15:22:21 GMT 2016 armv7l GNU/Linux
• Subsystem: fs.readFileSync

Situation:

I'm trying to capture my RPi3's mac addresses using synchronous file reading, getting information from my host system at `/sys/class/net/*/address`.

Action:

I have two branches at this repo: https://github.com/noncreature0714/gen-sys-id-node.git

Branch master is the asynchronous version, and works successfully.
Branch sync-test is synchronous, and is not working as expected - almost as if it never ran synchronously.

Results:

Output of 'master' (asynchronous) branch is:

ifs.eth0: "my correct eth0 mac address here"
ifs.wlan0: "my correct wlan0 mac address here"

Output of 'sync-test' branch is:

ifs.eth0: function String() { [native code]}
ifs.wlan0: function String() { [native code]}

Summary

The values where never assigned, almost like what happens when asynchronous operations occur after accessing variables. Additionally, the `console.log()` inside the functions never logs. Which leads me to consider the possibility that `readFileSync` may not be working at all.

[addaleax]

You can’t use fs.readFileSync with callbacks, it just gives you the file contents as the return value. You’ll have to write something like this:

ifs.eth0 = fs.readFileSync('/sys/class/net/eth0/address');

etc.

I’ll be closing this as it’s very likely not an issue with node core, but if you have any trouble getting this to work, please open an issue at https://github.com/nodejs/help :)

[noncreature0714]

@addaleax I think Homer Simpson has a word for this... But thanks!