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> Yes, /dev/(u)random is supposed to do that, [...] getrandom() is often times suggested, but alas isn’t a standardized function, i.e. it’s not part of the POSIX specification.

Is /dev/random or /dev/urandom part of the POSIX specification?

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Neither one is last time I looked. I’m a lot more uptight about POSIX compliance with code that needs to compile than I am with code that just needs a special /dev file to run, for the simple reason, when using POSIX during the compile stage, I can place the blame on GCC and/or clang if the program doesn’t compile when my program is POSIX and C99 compliant (I was, like many, burned by the C23 changes which made a lot of code which previously used to compile no longer compile).

I actually at one time had a Windows binary which would use Windows proprietary calls to make a “urandom” file (secret.txt was its name) so people could have good entropy on systems using the exact same interface as fopen("/dev/urandom","rb") (i.e fopen("secret.txt","rb")) without needing an actual /dev/urandom.

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