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  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.

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 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.

SEE ALSO
       splice(2), tee(2)

COLOPHON
       This  page  is  part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2014-10-02                                VMSPLICE(2)