ioctl

Purpose

     Controls input/output devices.

Syntax

     #include <sys/ioctl.h>
     #include <sys/devinfo.h>

     int ioctl (fildes, op, arg)
     int fildes, op;
     char *arg;

Description

     The ioctl system call performs a variety of control oper-
     ations on  the block  or character special  file (device)
     specified  by the  fildes  parameter.   The op  parameter
     specifies the operation, and the use of the arg parameter
     depends on the particular operation performed.  The ioctl
     operations that  are valid  for each  type of  device are
     explained in Chapter 4, "Special  Files." For more infor-
     mation on the  ioctl operations for use  with sockets and
     4.3BSD functions, see "socket" and "BSD 4.3 library."

     Two operations  are valid for  all types of  devices that
     support ioctl system call.  These two operations are:

     IOCTYPE     Returns  the  device   type  associated  with
                 fildes.  The device types  are defined in the
                 sys/devinfo.h header file, which is discussed
                 in "devinfo."

     IOCINFO     Stores device information for the file speci-
                 fied by fildes into  the buffer pointed to by
                 the  arg parameter.   See  "devinfo" for  the
                 format of the device information structure.

     Some devices  support additional requests.  See  the dis-
     cussion  of  individual  devices  in  Chapter 4, "Special
     Files" for details about device-dependent ioctl calls.

Return Value

     If ioctl  fails, a value of  -1 is returned and  errno is
     set to indicate the error.

Diagnostics

     The ioctl fails if one or more of the following are true:

     EBADF      fildes is not a valid open file descriptor.

     ENOTTY     fildes  is  not  associated with  a  character
                special file.

     ENODEV     The  device associated  with  fildes does  not
                support the ioctl system call.

     EFAULT     The arg parameter &pointsout..

     EINVAL     op or arg is not valid.

     EINTR      A signal  was caught  during the  ioctl system
                call.

Related Information

     In  this   book:   "devinfo,"   and   Chapter 4, "Special
     Files."

     The discussion  of ddioctl  in Device  Driver Development
     Guide.

     The discussion of termio in AIX Operating System Program-
     ming Tools and Interfaces.