NAME

getentropy — get entropy

SYNOPSIS

#include <unistd.h>

int
getentropy(void *buf, size_t buflen);

DESCRIPTION

getentropy() fills a buffer with high-quality entropy, which can be used as input for process-context pseudorandom generators like arc4random(3).

The maximum buffer size permitted is 256 bytes.

getentropy() is not intended for regular code; please use the arc4random(3) family of functions instead.

The high-quality entropy data is provided by the random(4) subsystem.

RETURN VALUES

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

getentropy() will succeed unless:

[EFAULT]

The buf parameter points to an invalid address.

[EIO]

Too many bytes requested, or some other fatal error occurred.

SEE ALSO

arc4random(3)

HISTORY

The getentropy() function appeared in OpenBSD 5.6.