NAME
vmsplice - splice user pages into a pipe SYNOPSIS
#define GNUSOURCE /* See featuretestmacros(7) */
#include
#include
ssizet vmsplice(int fd, const struct iovec *iov, unsigned long nrsegs, unsigned int flags); DESCRIPTION The vmsplice() system call maps nrsegs 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 : struct iovec { void *iovbase; /* Starting address */ sizet iovlen; /* Number of bytes */ }; The flags argument is a bit mask that is composed by ORing together zero or more of the following values: SPLICEFMOVE Unused for vmsplice(); see splice(2). SPLICEFNONBLOCK Do not block on I/O; see splice(2) for further details. SPLICEFMORE Currently has no effect for vmsplice(), but may be implemented in the future; see splice(2). SPLICEFGIFT The user pages are a gift to the kernel. The appli‐ cation 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) SPLICEFMOVE can successfully move the pages; if this flag is not specified, then a subsequent splice(2) SPLICEFMOVE 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 nrsegs is 0 or greater than IOVMAX; or memory not aligned if SPLICEFGIFT 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 number of segments being passed in. This limit is IOVMAX as defined in
. At the time of this writ‐ ing, that limit is 1024. SEE ALSO splice(2), tee(2) COLOPHON This page is part of release 3.53 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/.
Linux 2012-05-04 VMSPLICE(2)