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 3.25 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)