VMSPLICE(2)						     Linux Programmer's Manual						       VMSPLICE(2)

NAME

       vmsplice - splice user pages into a pipe

SYNOPSIS

       #define _GNU_SOURCE
       #include <fcntl.h>
       #include <sys/uio.h>

       ssize_t vmsplice(int fd, const struct iovec *iov,
			unsigned long nr_segs, unsigned int flags);

DESCRIPTION

       The vmsplice() system call maps nr_segs ranges of user memory described by iov into a pipe.  The file descriptor fd must refer to a pipe.

       The pointer iov points to an array of iovec structures as defined in <sys/uio.h>:

	   struct iovec {
	       void  *iov_base; 	   /* Starting address */
	       size_t iov_len;		   /* Number of bytes */
	   };

       The flags argument is a bit mask that is composed by ORing together zero or more of the following values:

       SPLICE_F_MOVE	  Unused for vmsplice(); see splice(2).

       SPLICE_F_NONBLOCK  Do not block on I/O; see splice(2) for further details.

       SPLICE_F_MORE	  Currently has no effect for vmsplice(), but may be implemented in the future; see splice(2).

       SPLICE_F_GIFT	  The  user  pages  are  a gift to the kernel.	The application may not modify this memory ever, or page cache and on-disk
			  data may differ.  Gifting pages to the kernel means that a subsequent splice(2) SPLICE_F_MOVE can successfully move  the
			  pages;  if this flag is not specified, then a subsequent splice(2) SPLICE_F_MOVE must copy the pages.  Data must also be
			  properly page aligned, both in memory and length.

RETURN VALUE

       Upon successful completion, vmsplice() returns the number of bytes transferred to the pipe.  On error, vmsplice() returns -1 and  errno	is
       set to indicate the error.

ERRORS

       EBADF  fd either not valid, or doesn't refer to a pipe.

       EINVAL nr_segs is 0 or greater than IOV_MAX; or memory not aligned if SPLICE_F_GIFT set.

       ENOMEM Out of memory.

VERSIONS

       The vmsplice() system call first appeared in Linux 2.6.17.

CONFORMING TO

       This system call is Linux-specific.

NOTES

       vmsplice() follows the other vectorized read/write type functions when it comes to limitations on number of segments being passed in.  This
       limit is IOV_MAX as defined in <limits.h>.  At the time of this writing, that limit is 1024.

SEE ALSO

       splice(2), tee(2), feature_test_macros(7)

COLOPHON

       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2009-09-15							       VMSPLICE(2)