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GETRANDOM(2)             DragonFly System Calls Manual            GETRANDOM(2)


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 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.

DragonFly 6.1-DEVELOPMENT      December 31, 2021     DragonFly 6.1-DEVELOPMENT

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