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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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vmsplice(2) System Calls Manual vmsplice(2)
vmsplice - splice user pages to/from a pipe
Standard C library (libc, -lc)
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <fcntl.h>
ssize_t vmsplice(int fd, const struct iovec *iov,
size_t nr_segs, unsigned int flags);
If fd is opened for writing, the vmsplice() system call maps
nr_segs ranges of user memory described by iov into a pipe. If fd
is opened for reading, the vmsplice() system call fills nr_segs
ranges of user memory described by iov from a pipe. The file
descriptor fd must refer to a pipe.
The pointer iov points to an array of iovec structures as
described in iovec(3type).
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.
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.
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.
Linux.
Linux 2.6.17, glibc 2.5.
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.
vmsplice() really supports true splicing only from user memory to
a pipe. In the opposite direction, it actually just copies the
data to user space. But this makes the interface nice and
symmetric and enables people to build on vmsplice() with room for
future improvement in performance.
splice(2), tee(2), pipe(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 vmsplice(2)
Pages that refer to this page: pipe(2), splice(2), syscalls(2), tee(2), pipe(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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