GETRANDOM(2)

NAME
getrandom - get random data

LIBRARY
libc

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 DragonFly. /dev/random and /dev/urandom are identical.

GRND_INSECURE
    This flag is treated as an alternative name for GRND_NONBLOCK. It is provided solely for API compatibility with Linux.

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 (or GRND_INSECURE) 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 is invalid (typically if negative). DragonFly does not impose a limit on the buffer size.

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

STANDARDS
getrandom() is non-standard. It is present in Linux.

HISTORY
The getrandom() system call first appeared in DragonFly 5.7.

CAVEATS
Unlike Linux, the GRND_INSECURE flag on DragonFly does not produce any output before the random(4) device is seeded.