ioctl()

Control a device

Synopsis:

#include <sys/ioctl.h> 

int ioctl( int fd, 
           int request, 
           ... );

Description:

The ioctl() function manipulates the underlying parameters of files. In particular, it can be used to control many of the operating attributes of files (such as the attributes of terminals).

The request argument determines whether the subsequent arguments are an "in" or "out" parameter; it also specifies the size of the arguments in bytes. Macros and defines used in specifying a request are located in the file <sys/ioctl.h>.

The argument fd must be an open file descriptor.

Returns:

A value based on the request, or -1 if an error occurs (errno is set).

Errors:

EBADF: Invalid descriptor fd.
EINVAL: The request or optional variables aren't valid.
ENOTTY: The fd argument isn't associated with a character special device; the specified request doesn't apply to the kind of object that the descriptor fd references.

Classification:

Standard Unix

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	No

Caveats:

The ioctl() function is a Unix function that varies greatly from platform to platform.