IOCTL(2) — SYSTEM CALLS

NAME

ioctl − control device

SYNOPSIS

#include <sys/ioctl.h>

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

DESCRIPTION

Ioctl performs a variety of functions on open descriptors. In particular, many operating characteristics of character special files (e.g. terminals) may be controlled with ioctl requests. The writeups of various devices in section 4 discuss how ioctl applies to them.

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.

If no error has occurred (using a STANDARD device driver), a value of 0 is returned.

ERRORS

Ioctl will fail if one or more of the following are true:

[EBADF] D is not a valid descriptor.

[ENOTTY] 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] Request or argp is not valid.

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