/dev/null sez nothing is also a file

You'll know you've reached stage 6 when you seriously start considering running Plan 9 as a daily driver

Unfortunately, no one can be told what a file is. You have to see it for yourself.

This is your last chance. After this, there is no turning back. You take the blue pill - the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill - you stay in Wonderland and I show you how deep the file system goes.

true enlightenment: everything is a string over an IO socket

Am I a file?

"How can files be real if the filesystem isn't real?" - Jaden Smith (probably)

Okay, but what are blocks then? A file is really just a bunch of blocked stacked together with the inode metadata also sitting on another block, so is everything just blocks or because you can emulate a block device on a filesystem, are blocks themselves files? If that last part is true then files are infinitely recursive and my head is starting to spin.

7. Everything is a FIFO

Files? In my Linux?

It's more likely than you think.

And the hidden 0th level that you only get after being nearly killed by a falling server rack:

"Files Aren't Things"

Which looks great on a tshirt, btw :p

Missing stage 7: Not everything is a file.

Linux is closer than other *nixes (sysctl equivalents in some platforms are not files, but they are files in Linux).

However get very far into network and the file-like behaviors become more limited. From an application, at least you have a decent chance of having unseekable, but otherwise 'file-like' interaction with stream protocols. Then you need recvmsg/sendmsg. Then you want to deal with low level interaction with the network stack and dealing with NETLINK and such..