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RedHat 9 (Linux i386) - man page for ioperm (redhat section 2)

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IOPERM(2)			    Linux Programmer's Manual				IOPERM(2)

       ioperm - set port input/output permissions

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

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

       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.

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

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

       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.


Linux					    1993-01-21					IOPERM(2)
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