vmsplice(2)

1vmsplice(2)                Linux Programmer's Manual               vmsplice(2)
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NAME

6       vmsplice - splice user pages into a pipe
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SYNOPSIS

9       #define _GNU_SOURCE
10       #include <fcntl.h>
11       #include <sys/uio.h>
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13       long vmsplice(int fd, const struct iovec *iov,
14                     unsigned long nr_segs, unsigned int flags);
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DESCRIPTION

17       The vmsplice() system call maps nr_segs ranges of user memory described
18       by iov into a pipe.  The file descriptor fd must refer to a pipe.
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20       The pointer iov points to an array of iovec structures  as  defined  in
21       <sys/uio.h>:
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23         struct iovec {
24             void  *iov_base;            /* Starting address */
25             size_t iov_len;             /* Number of bytes */
26         };
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28       The  flags  argument  is  a bit mask that is composed by ORing together
29       zero or more of the following values:
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31       SPLICE_F_MOVE      Unused for vmsplice(); see splice(2).
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33       SPLICE_F_NONBLOCK  Do not block  on  I/O;  see  splice(2)  for  further
34                          details.
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36       SPLICE_F_MORE      Currently  has  no effect for vmsplice(), but may be
37                          implemented in the future; see splice(2).
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39       SPLICE_F_GIFT      The user pages are a gift to the kernel.  The appli‐
40                          cation  may  not  modify  this  memory ever, or page
41                          cache and on-disk data may differ.  Gifting pages to
42                          the   kernel   means   that  a  subsequent  splice()
43                          SPLICE_F_MOVE can successfully move  the  pages;  if
44                          this  flag  is  not  specified,  then  a  subsequent
45                          splice() SPLICE_F_MOVE must copy  the  pages.   Data
46                          must  also  be properly page aligned, both in memory
47                          and length.
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RETURN VALUE

50       Upon successful completion, vmsplice()  returns  the  number  of  bytes
51       transferred  to  the pipe.  On error, vmplice() returns -1 and errno is
52       set to indicate the error.
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ERRORS

55       EBADF  fd either not valid, or doesn't refer to a pipe.
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57       EINVAL nr_segs is 0 or greater than IOV_MAX; or memory not  aligned  if
58              SPLICE_F_GIFT set.
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60       ENOMEM Out of memory.
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NOTES

63       vmsplice()  follows the other vectorized read/write type functions when
64       it comes to limitations on number of segments being  passed  in.   This
65       limit  is  IOV_MAX as defined in <limits.h>.  At the time of this writ‐
66       ing, that limit is 1024.
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HISTORY

69       The vmsplice(2) system call first appeared in Linux-2.6.17.
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CONFORMING TO

72       This system call is Linux specific.
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