Section (3) getentropy
getentropy — fill a buffer with random bytes
of high-quality random data to the buffer starting at the
location pointed to by
buffer. The maximum permitted
value for the
argument is 256.
A successful call to
getentropy() always provides the requested
number of bytes of entropy.
On success, this function returns zero. On error, −1
is returned, and
errno is set
Part or all of the buffer specified by
lengthis not in valid addressable memory.
lengthis greater than 256.
An unspecified error occurred while trying to overwrite
bufferwith random data.
This kernel version does not implement the getrandom(2) system call required to implement this function.
getentropy() function is
implemented using getrandom(2).
Whereas the glibc wrapper makes getrandom(2) a cancellation
getentropy() is not a
getentropy() is also
> (No feature test macro need be defined
to obtain the declaration from that header file.)
A call to
block if the system has just booted and the kernel has not
yet collected enough randomness to initialize the entropy
pool. In this case,
getentropy() will keep blocking even if a
signal is handled, and will return only once the entropy pool
has been initialized.
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