I got about halfway through "A terminal case of Linux" which is about terminals, syscalls and stuff like that. An interesting read!
https://fasterthanli.me/articles/a-terminal-case-of-linux

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Then it returns -1, which strace helpfully translates to ENOTTY, ie. "error not a TTY".
So that means... we can make that syscall ourselves!

Found via https://fosstodon.org/@esoteric_programmer@social.stealthy.club/111930232259064492 by @esoteric_programmer