1sys_uio.h(0P) POSIX Programmer's Manual sys_uio.h(0P)
2
3
4
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.
10
12 sys/uio.h — definitions for vector I/O operations
13
15 #include <sys/uio.h>
16
18 The <sys/uio.h> header shall define the iovec structure, which shall
19 include at least the following members:
20
21
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.
24
25 The <sys/uio.h> header uses the iovec structure for scatter/gather I/O.
26
27 The <sys/uio.h> header shall define the ssize_t and size_t types as
28 described in <sys/types.h>.
29
30 The following shall be declared as functions and may also be defined as
31 macros. Function prototypes shall be provided.
32
33
34 ssize_t readv(int, const struct iovec *, int);
35 ssize_t writev(int, const struct iovec *, int);
36
37 The following sections are informative.
38
40 The implementation can put a limit on the number of scatter/gather ele‐
41 ments which can be processed in one call. The symbol {IOV_MAX} defined
42 in <limits.h> should always be used to learn about the limits instead
43 of assuming a fixed value.
44
46 Traditionally, the maximum number of scatter/gather elements the system
47 can process in one call were described by the symbolic value {UIO_MAX‐
48 IOV}. In IEEE Std 1003.1‐2001 this value is replaced by the constant
49 {IOV_MAX} which can be found in <limits.h>.
50
52 None.
53
55 <limits.h>, <sys_types.h>
56
57 The System Interfaces volume of POSIX.1‐2017, read(), readv(), write(),
58 writev()
59
61 Portions of this text are reprinted and reproduced in electronic form
62 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
63 table Operating System Interface (POSIX), The Open Group Base Specifi‐
64 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
65 Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
70
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 .
75
76
77
78IEEE/The Open Group 2017 sys_uio.h(0P)