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

NAME

       vmsplice - splice user pages into a pipe

SYNOPSIS

       #define _GNU_SOURCE	   /* See feature_test_macros(7) */
       #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, otherwise the 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

       EAGAIN SPLICE_F_NONBLOCK was specified in flags, and the operation would block.

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

       EINVAL nr_segs is 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; library support was added to glibc in version 2.5.

CONFORMING TO

       This system call is Linux-specific.

NOTES

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

SEE ALSO

       splice(2), tee(2), pipe(7)

COLOPHON

       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/.

Linux								    2017-09-15							       VMSPLICE(2)