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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>

       long 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 descrip-
       tor 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  subse-
                          quent  splice(2)  SPLICE_F_MOVE  can successfully move the pages; if this flag is not speci-
                          fied, 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 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2006-04-28                       VMSPLICE(2)