getentropy - fill a buffer with random bytes
On success, this function returns zero. On error, -1 is returned, and
errno is set appropriately.
Part or all of the buffer specified by
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.
The getentropy() function first appeared in glibc 2.25.
This function is nonstandard. It is also present on OpenBSD.
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.
This page is part of release 4.15 of the Linux
man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.