getentropy(3) Library Functions Manual getentropy(3) getentropy - (libc -lc) #include int getentropy(size_t length; void buffer[length], size_t length); glibc ( feature_test_macros(7)): getentropy(): _DEFAULT_SOURCE getentropy() length buffer. length 256. getentropy() . . -1 errno . EFAULT buffer length . EIO length 256. EIO buffer . ENOSYS getrandom(2) . POSIX.1-2024. OpenBSD 5.6, glibc 2.25, FreeBSD 12.0, POSIX.1-2024. getentropy() getrandom(2). glibc getrandom(2) getentropy() . getentropy() . ( .) getentropy() . getentropy() . getrandom(2), urandom(4), random(7) 3 . . : . 6.18 21 2026 getentropy(3)