NAME
getentropy —
get entropy
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
int
getentropy(void
*buf, size_t
buflen);
DESCRIPTION
getentropy()
fills a buffer with high-quality random data.
The maximum buflen permitted is 256 bytes.
If it does not produce an error,
getentropy()
always provides the requested number of bytes of random data.
Similar to reading from
/dev/urandom just after boot,
getentropy()
may block until the system has collected enough entropy to seed the
CSPRNG.
IMPLEMENTATION NOTES
The getentropy() function is implemented
using getrandom(2).
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
STANDARDS
getentropy() is non-standard. It is
present on OpenBSD and Linux.
HISTORY
The getentropy() function appeared in
OpenBSD 5.6. The FreeBSD
libc compatibility shim first appeared in FreeBSD
12.0.