vmsplice(2)



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 sup-
       port 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 4.16 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)

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