Manpage of VMSPLICE

VMSPLICE

Section: Linux Programmer's Manual (2)
Updated: 2014-10-02
Index
 

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_segsranges of user memory described by iovinto a pipe. The file descriptor fdmust refer to a pipe.

The pointer iovpoints to an array of iovecstructures as defined in <sys/uio.h>:

struct iovec {
    void  *iov_base;        /* Starting address */
    size_t iov_len;         /* Number of bytes */
};

The flagsargument 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_MOVEcan successfully move the pages; if this flag is not specified, then a subsequent splice(2) SPLICE_F_MOVEmust 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 errnois set to indicate the error.  

ERRORS

EAGAIN
SPLICE_F_NONBLOCKwas specified in flags, and the operation would block.
EBADF
fdeither not valid, or doesn't refer to a pipe.
EINVAL
nr_segsis greater than IOV_MAX; or memory not aligned if SPLICE_F_GIFTset.
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_MAXas defined in <limits.h>. Currently, this limit is 1024.  

SEE ALSO

splice(2), tee(2)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
SEE ALSO

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