ioctl(2)

Name

ioctl − control device

Syntax

#include <sys/ioctl.h>

ioctl(d, request, argp)
int d, request;
char *argp;

Description

The ioctl call performs a variety of functions on open descriptors. In particular, many operating characteristics of character special files (for example, terminals) can be controlled with ioctl requests. Certain ioctl requests operate on a number of device types. These include informational ioctl requests, such as devio and nbuf. The descriptions of various devices in the Reference Pages, Section 4: Special Files discuss how ioctl applies to them. Also consult <sys/ioctl.h> for more information.

An ioctl request has encoded in it whether the argument is an “in” parameter or “out” parameter, and the size of the argument argp in bytes. Macros and defines used in specifying an ioctl request are located in the file <sys/ioctl.h>.

Return Value

If an error has occurred, a value of −1 is returned, and errno is set to indicate the error.

Diagnostics

The ioctl call fails under the following conditions:

[EBADF] The d is not a valid descriptor.

[ENOTTY] The d is not associated with a character special device.

[ENOTTY] The specified request does not apply to the kind of object which the descriptor d references.

[EINVAL] The request or argp is not valid.

[EFAULT] The argp points to memory that is not part of the process’ address space.

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