1sys_uio.h(0P)              POSIX Programmer's Manual             sys_uio.h(0P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       sys/uio.h — definitions for vector I/O operations
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SYNOPSIS

16       #include <sys/uio.h>
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DESCRIPTION

19       The <sys/uio.h> header shall define the iovec  structure,  which  shall
20       include at least the following members:
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22           void   *iov_base  Base address of a memory region for input or output.
23           size_t  iov_len   The size of the memory pointed to by iov_base.
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25       The <sys/uio.h> header uses the iovec structure for scatter/gather I/O.
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27       The  <sys/uio.h>  header  shall  define the ssize_t and size_t types as
28       described in <sys/types.h>.
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30       The following shall be declared as functions and may also be defined as
31       macros. Function prototypes shall be provided.
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33           ssize_t readv(int, const struct iovec *, int);
34           ssize_t writev(int, const struct iovec *, int);
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36       The following sections are informative.
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APPLICATION USAGE

39       The implementation can put a limit on the number of scatter/gather ele‐
40       ments which can be processed in one call. The symbol {IOV_MAX}  defined
41       in  <limits.h>  should always be used to learn about the limits instead
42       of assuming a fixed value.
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RATIONALE

45       Traditionally, the maximum number of scatter/gather elements the system
46       can  process in one call were described by the symbolic value {UIO_MAX‐
47       IOV}.  In IEEE Std 1003.1‐2001 this value is replaced by  the  constant
48       {IOV_MAX} which can be found in <limits.h>.
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FUTURE DIRECTIONS

51       None.
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SEE ALSO

54       <limits.h>, <sys_types.h>
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56       The System Interfaces volume of POSIX.1‐2008, read(), readv(), write(),
57       writev()
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60       Portions of this text are reprinted and reproduced in  electronic  form
61       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
62       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
63       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
64       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
65       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
66       event of any discrepancy between this version and the original IEEE and
67       The  Open Group Standard, the original IEEE and The Open Group Standard
68       is the referee document. The original Standard can be  obtained  online
69       at http://www.unix.org/online.html .
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71       Any  typographical  or  formatting  errors that appear in this page are
72       most likely to have been introduced during the conversion of the source
73       files  to  man page format. To report such errors, see https://www.ker‐
74       nel.org/doc/man-pages/reporting_bugs.html .
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78IEEE/The Open Group                  2013                        sys_uio.h(0P)
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