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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | VERSIONS | STANDARDS | SEE ALSO | COLOPHON |
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outb(2) System Calls Manual outb(2)
outb, outw, outl, outsb, outsw, outsl, inb, inw, inl, insb, insw,
insl, outb_p, outw_p, outl_p, inb_p, inw_p, inl_p - port I/O
Standard C library (libc, -lc)
#include <sys/io.h>
unsigned char inb(unsigned short port);
unsigned char inb_p(unsigned short port);
unsigned short inw(unsigned short port);
unsigned short inw_p(unsigned short port);
unsigned int inl(unsigned short port);
unsigned int inl_p(unsigned short port);
void outb(unsigned char value, unsigned short port);
void outb_p(unsigned char value, unsigned short port);
void outw(unsigned short value, unsigned short port);
void outw_p(unsigned short value, unsigned short port);
void outl(unsigned int value, unsigned short port);
void outl_p(unsigned int value, unsigned short port);
void insb(unsigned short port, void addr[.count],
unsigned long count);
void insw(unsigned short port, void addr[.count],
unsigned long count);
void insl(unsigned short port, void addr[.count],
unsigned long count);
void outsb(unsigned short port, const void addr[.count],
unsigned long count);
void outsw(unsigned short port, const void addr[.count],
unsigned long count);
void outsl(unsigned short port, const void addr[.count],
unsigned long count);
This family of functions is used to do low-level port input and
output. The out* functions do port output, the in* functions do
port input; the b-suffix functions are byte-width and the w-
suffix functions word-width; the _p-suffix functions pause until
the I/O completes.
They are primarily designed for internal kernel use, but can be
used from user space.
You must compile with -O or -O2 or similar. The functions are
defined as inline macros, and will not be substituted in without
optimization enabled, causing unresolved references at link time.
You use ioperm(2) or alternatively iopl(2) to tell the kernel to
allow the user space application to access the I/O ports in
question. Failure to do this will cause the application to
receive a segmentation fault.
outb() and friends are hardware-specific. The value argument is
passed first and the port argument is passed second, which is the
opposite order from most DOS implementations.
None.
ioperm(2), iopl(2)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 outb(2)
Pages that refer to this page: ioperm(2), iopl(2)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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