# outb

## NAME



           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
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#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 long count;
                      **unsigned short** _port_**, void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
           **void insw(** unsigned long count;
                      **unsigned short** _port_**, void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
           **void insl(** unsigned long count;
                      **unsigned short** _port_**, void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
           **void outsb(** unsigned long count;
                      **unsigned short** _port_**, const void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
           **void outsw(** unsigned long count;
                      **unsigned short** _port_**, const void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
           **void outsl(** unsigned long count;
                      **unsigned short** _port_**, const void** _addr_**[**_count_**],**
                      **unsigned long** _count_**);**
    


## DESCRIPTION



           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.
    


## VERSIONS



           **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.
    


## STANDARDS



           None.
    


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