trusty (2) vmsplice.2.gz

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, 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; 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 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)

COLOPHON

       This  page  is  part  of  release 3.54 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/.