|GETENTROPY(3)||Linux Programmer's Manual||GETENTROPY(3)|
int getentropy(void *buffer, size_t length);
A successful call to getentropy() always provides the requested number of bytes of entropy.
- Part or all of the buffer specified by buffer and length is not in valid addressable memory.
- length is greater than 256.
- An unspecified error occurred while trying to overwrite buffer with random data.
- This kernel version does not implement the getrandom(2) system call required to implement this function.
Whereas the glibc wrapper makes getrandom(2) a cancellation point, getentropy() is not a cancellation point.
getentropy() is also declared in <sys/random.h>. (No feature test macro need be defined to obtain the declaration from that header file.)
A call to getentropy() may 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.