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         /* See feature_test_macros(7) */
10       #include <fcntl.h>
11       #include <sys/uio.h>
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13       ssize_t 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
32              Unused for vmsplice(); see splice(2).
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34       SPLICE_F_NONBLOCK
35              Do not block on I/O; see splice(2) for further details.
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37       SPLICE_F_MORE
38              Currently has no effect for vmsplice(), but may  be  implemented
39              in the future; see splice(2).
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41       SPLICE_F_GIFT
42              The  user  pages  are a gift to the kernel.  The application may
43              not modify this memory ever, otherwise the page  cache  and  on-
44              disk  data may differ.  Gifting pages to the kernel means that a
45              subsequent splice(2) SPLICE_F_MOVE  can  successfully  move  the
46              pages;  if  this  flag  is  not  specified,  then  a  subsequent
47              splice(2) SPLICE_F_MOVE must copy the pages.  Data must also  be
48              properly page aligned, both in memory and length.
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RETURN VALUE

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

56       EAGAIN SPLICE_F_NONBLOCK  was  specified  in  flags,  and the operation
57              would block.
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59       EBADF  fd either not valid, or doesn't refer to a pipe.
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61       EINVAL nr_segs is greater  than  IOV_MAX;  or  memory  not  aligned  if
62              SPLICE_F_GIFT set.
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64       ENOMEM Out of memory.
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VERSIONS

67       The vmsplice() system call first appeared in Linux 2.6.17; library sup‐
68       port was added to glibc in version 2.5.
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CONFORMING TO

71       This system call is Linux-specific.
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NOTES

74       vmsplice() follows the other vectorized read/write type functions  when
75       it  comes  to  limitations  on  the number of segments being passed in.
76       This limit is IOV_MAX as defined in <limits.h>.  Currently, this  limit
77       is 1024.
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COLOPHON

83       This  page  is  part of release 4.15 of the Linux man-pages project.  A
84       description of the project, information about reporting bugs,  and  the
85       latest     version     of     this    page,    can    be    found    at
86       https://www.kernel.org/doc/man-pages/.
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90Linux                             2017-09-15                       VMSPLICE(2)