sys_uio.h(0P) POSIX Programmer's Manual sys_uio.h(0P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
sys/uio.h — definitions for vector I/O operations
SYNOPSIS
#include <sys/uio.h>
DESCRIPTION
The <sys/uio.h> header shall define the iovec structure, which shall
include at least the following members:
void *iov_base Base address of a memory region for input or output.
size_t iov_len The size of the memory pointed to by iov_base.
The <sys/uio.h> header uses the iovec structure for scatter/gather I/O.
The <sys/uio.h> header shall define the ssize_t and size_t types as
described in <sys/types.h>.
The following shall be declared as functions and may also be defined as
macros. Function prototypes shall be provided.
ssize_t readv(int, const struct iovec *, int);
ssize_t writev(int, const struct iovec *, int);
The following sections are informative.
APPLICATION USAGE
The implementation can put a limit on the number of scatter/gather ele‐
ments which can be processed in one call. The symbol {IOV_MAX} defined
in <limits.h> should always be used to learn about the limits instead
of assuming a fixed value.
RATIONALE
Traditionally, the maximum number of scatter/gather elements the system
can process in one call were described by the symbolic value {UIO_MAX‐
IOV}. In IEEE Std 1003.1‐2001 this value is replaced by the constant
{IOV_MAX} which can be found in <limits.h>.
FUTURE DIRECTIONS
None.
SEE ALSO
<limits.h>, <sys_types.h>
The System Interfaces volume of POSIX.1‐2008, read(), readv(), write(),
writev()COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 sys_uio.h(0P)
