1READV(3P)                  POSIX Programmer's Manual                 READV(3P)
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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

12       readv - read a vector
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SYNOPSIS

15       #include <sys/uio.h>
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17       ssize_t readv(int fildes, const struct iovec *iov, int iovcnt);
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DESCRIPTION

21       The readv() function shall be equivalent to read(), except as described
22       below.  The readv() function shall place the input data into the iovcnt
23       buffers specified by the members of the iov array: iov[0], iov[1], ...,
24       iov[  iovcnt-1].   The  iovcnt  argument is valid if greater than 0 and
25       less than or equal to {IOV_MAX}.
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27       Each iovec entry specifies the base address and length of  an  area  in
28       memory  where  data should be placed. The readv() function shall always
29       fill an area completely before proceeding to the next.
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31       Upon successful completion, readv() shall mark for update the  st_atime
32       field of the file.
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RETURN VALUE

35       Refer to read().
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ERRORS

38       Refer to read().
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40       In addition, the readv() function shall fail if:
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42       EINVAL The  sum  of  the  iov_len values in the iov array overflowed an
43              ssize_t.
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46       The readv() function may fail if:
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48       EINVAL The iovcnt argument was less than or equal to 0, or greater than
49              {IOV_MAX}.
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52       The following sections are informative.
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EXAMPLES

55   Reading Data into an Array
56       The following example reads data from the file associated with the file
57       descriptor fd into the buffers specified by members of the iov array.
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60              #include <sys/types.h>
61              #include <sys/uio.h>
62              #include <unistd.h>
63              ...
64              ssize_t bytes_read;
65              int fd;
66              char buf0[20];
67              char buf1[30];
68              char buf2[40];
69              int iovcnt;
70              struct iovec iov[3];
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73              iov[0].iov_base = buf0;
74              iov[0].iov_len = sizeof(buf0);
75              iov[1].iov_base = buf1;
76              iov[1].iov_len = sizeof(buf1);
77              iov[2].iov_base = buf2;
78              iov[2].iov_len = sizeof(buf2);
79              ...
80              iovcnt = sizeof(iov) / sizeof(struct iovec);
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83              bytes_read = readv(fd, iov, iovcnt);
84              ...
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APPLICATION USAGE

87       None.
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RATIONALE

90       Refer to read().
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FUTURE DIRECTIONS

93       None.
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SEE ALSO

96       read(), writev(), the Base Definitions volume of  IEEE Std 1003.1-2001,
97       <sys/uio.h>
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100       Portions  of  this text are reprinted and reproduced in electronic form
101       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
102       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
103       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
104       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
105       event of any discrepancy between this version and the original IEEE and
106       The  Open Group Standard, the original IEEE and The Open Group Standard
107       is the referee document. The original Standard can be  obtained  online
108       at http://www.opengroup.org/unix/online.html .
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112IEEE/The Open Group                  2003                            READV(3P)
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