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GETENTROPY(2)               BSD System Calls Manual              GETENTROPY(2)

NAME
     getentropy -- get entropy

SYNOPSIS
     #include <&lt;unistd.h>&gt;

     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.  If buflen exceeds this,
     an error of EIO will be indicated.

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

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.

BSD                             April 28, 2017                             BSD