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Command: getentropy | Section: 2 | Source: OpenBSD | File: getentropy.2
GETENTROPY(2) FreeBSD System Calls Manual GETENTROPY(2)
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 GETENTROPY_MAX (256) bytes.
getentropy() is not intended for regular code; 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.
[EINVAL] Too many bytes requested.
SEE ALSO
arc4random(3)
STANDARDS
The getentropy() function conforms to.
HISTORY
The getentropy() function appeared in OpenBSD 5.6.
FreeBSD 14.1-RELEASE-p8 August 2, 2024 FreeBSD 14.1-RELEASE-p8