getentropy —
get entropy
#include
<unistd.h>
int
getentropy(
void
*buf,
size_t
buflen);
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.
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.
getentropy() will succeed unless:
-
-
- [
EFAULT]
- The buf parameter points to an invalid
address.
-
-
- [
EIO]
- Too many bytes requested, or some other fatal error occurred.
arc4random(3)
The
getentropy() function appeared in
OpenBSD 5.6.
![[OpenBSD]](/openbsd.gif){kind=small}