GNU/Linux man pages
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Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.2 |
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vmsplice(2) |
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vmsplice − splice user pages into a pipe
#define
_GNU_SOURCE
#include <fcntl.h>
#include <sys/uio.h>
long
vmsplice(int fd, const struct iovec
*iov,
unsigned long nr_segs, unsigned int
flags);
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:
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SPLICE_F_MOVE |
Unused for vmsplice(); see splice(2). | ||
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SPLICE_F_NONBLOCK |
Do not block on I/O; see splice(2) for further details. | ||
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SPLICE_F_MORE |
Currently has no effect for vmsplice(), but may be implemented in the future; see splice(2). | ||
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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() SPLICE_F_MOVE can successfully move the pages; if this flag is not specified, then a subsequent splice() 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, vmplice() returns −1 and errno is set to indicate the error.
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EBADF |
fd either not valid, or doesn’t refer to a pipe. | ||
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EINVAL |
nr_segs is 0 or greater than IOV_MAX; or memory not aligned if SPLICE_F_GIFT set. | ||
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ENOMEM |
Out of memory. |
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.
The vmsplice(2) system call first appeared in Linux-2.6.17.
This system call is Linux specific.
splice(2), tee(2)
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vmsplice(2) | |