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NAME    [Toc]    [Back]

       ioperm - set port input/output permissions

SYNOPSIS    [Toc]    [Back]

       #include <unistd.h> /* for libc5 */
       #include <sys/io.h> /* for glibc */

       int ioperm(unsigned long from, unsigned long num, int turn_on);

DESCRIPTION    [Toc]    [Back]

       Ioperm  sets  the  port	access permission bits for the process for num
       bytes starting from port address from to the value turn_on.  The use of
       ioperm requires root privileges.

       Only  the  first  0x3ff I/O ports can be specified in this manner.  For
       more ports, the iopl function must be used.  Permissions are not inherited
  on  fork,	but  on  exec they are. This is useful for giving port
       access permissions to non-privileged tasks.

RETURN VALUE    [Toc]    [Back]

       On success, zero is returned.  On error, -1 is returned, and  errno  is
       set appropriately.

CONFORMING TO    [Toc]    [Back]

       ioperm is Linux specific and should not be used in programs intended to
       be portable.

NOTES    [Toc]    [Back]

       Libc5 treats it as a system call and has  a  prototype  in  <unistd.h>.
       Glibc1  does  not  have	a  prototype.  Glibc2  has a prototype both in
       <sys/io.h> and in <sys/perm.h>.	Avoid the latter, it is  available  on
       i386 only.

SEE ALSO    [Toc]    [Back]


Linux				  1993-01-21			     IOPERM(2)
[ Back ]
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