arc4random

arc4random(3) is random-number-generating library function, first available on BSD platforms, and also on GNU/Linux with libbsd.

Manual pages

http://man.openbsd.org/?query=arc4random

https://www.freebsd.org/cgi/man.cgi?query=arc4random

https://manpages.debian.org/cgi-bin/man.cgi?query=arc4random