NAME

       getrandom — get random data

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <sys/random.h>

       ssize_t
       getrandom(void *buf, size_t buflen, unsigned int flags);

DESCRIPTION

       getrandom() fills buf with up to buflen bytes of random data.

       The flags argument may include zero or more of the following:

       ‘GRND_NONBLOCK’  Return  EAGAIN instead of blocking, if the random(4) device has not yet been seeded.  By
                        default, getrandom() will block until the device is seeded.

       ‘GRND_RANDOM’    This flag does nothing on FreeBSD.  /dev/random and /dev/urandom are identical.

       If the random(4) device has been seeded, reads of up to 256 bytes will always return  as  many  bytes  as
       requested and will not be interrupted by signals.

RETURN VALUES

       Upon  successful  completion,  the  number  of  bytes which were actually read is returned.  For requests
       larger than 256 bytes, this can be fewer bytes than were requested.  Otherwise, -1 is  returned  and  the
       global variable errno is set to indicate the error.

ERRORS

       The getrandom() operation returns the following errors:

       [EAGAIN]           The ‘GRND_NONBLOCK’ flag was set and the random(4) device was not yet seeded.

       [EFAULT]           The buf parameter points to an invalid address.

       [EINTR]            The sleep was interrupted by a signal.

       [EINVAL]           An invalid flags was specified.

       [EINVAL]           The requested buflen was larger than IOSIZE_MAX.

SEE ALSO

       arc4random(3), getentropy(3), random(4)

STANDARDS

       getentropy() is non-standard.  It is present in Linux.

HISTORY

       The getrandom() system call first appeared in FreeBSD 12.0.

Debian                                          February 24, 2018                                   GETRANDOM(2)