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Linux 2.6 - man page for vmsplice (linux section 2)

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

       vmsplice - splice user pages into a pipe

       #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);

       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  mod-
			  ify this memory ever, or page cache and on-disk data may differ.  Gift-
			  ing 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.

       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.

       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.

       The vmsplice() system call first appeared in Linux 2.6.17; library support  was	added  to
       glibc in version 2.5.

       This system call is Linux-specific.

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

       splice(2), tee(2)

       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

Linux					    2012-05-04				      VMSPLICE(2)

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