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    The following form allows you to view linux man pages.

    Command:

    iopl

    
    
    

    SYNOPSIS

           #include <sys/io.h>
    
           int iopl(int level);
    
    
    

    DESCRIPTION

           iopl() changes the I/O privilege level of the calling process, as spec-
           ified by the two least significant bits in level.
    
           This call is necessary to allow 8514-compatible X servers to run  under
           Linux.   Since  these  X servers require access to all 65536 I/O ports,
           the ioperm(2) call is not sufficient.
    
           In addition to granting unrestricted I/O  port  access,  running  at  a
           higher  I/O  privilege  level also allows the process to disable inter-
           rupts.  This will probably crash the system, and is not recommended.
    
           Permissions are inherited by fork(2) and execve(2).
    
           The I/O privilege level for a normal process is 0.
    
           This call is mostly for the i386 architecture.  On many other architec-
           tures it does not exist or will always return an error.
    
    
    

    RETURN VALUE

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

    ERRORS

           EINVAL level is greater than 3.
    
           ENOSYS This call is unimplemented.
    
           EPERM  The calling process has insufficient privilege to  call  iopl();
                  the CAP_SYS_RAWIO capability is required to raise the I/O privi-
                  lege level above its current value.
    
    
    

    CONFORMING TO

           iopl() is Linux-specific and should not be used in  programs  that  are
           intended to be portable.
    
    
    

    NOTES

           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

           ioperm(2), outb(2), capabilities(7)
    
    
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