bionic (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,
              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 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  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

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