Ioctl – Comtrol eCos User Manual

Page 566

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Chapter 38. TCP/IP Library Reference

ioctl

IOCTL(2)

System Calls Manual

IOCTL(2)

NAME

ioctl - control device

SYNOPSIS

#include

sys/ioctl.h>

int

ioctl(int d, unsigned long request, ...);

DESCRIPTION

The ioctl() function manipulates the underlying device parameters of spe-

cial files.

In particular, many operating characteristics of character

special files (e.g., terminals) may be controlled with ioctl() requests.

The argument d must be an open file descriptor. The third argument is

called arg and contains additional information needed by this device to

perform the requested function.

arg is either an int or a pointer to a

device-specific data structure, depending upon the given request.

An ioctl request has encoded in it whether the argument is an “in”

parameter or “out” parameter, and the size of the third argument (arg)

in bytes.

Macros and defines used in specifying an ioctl request are

located in the file

sys/ioctl.h>.

RETURN VALUES

If an error has occurred, a value of -1 is returned and errno is set to

indicate the error.

ERRORS

ioctl() will fail if:

[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 that the descriptor d references.

[EINVAL]

request or arg is not valid.

[EFAULT]

arg points outside the process’s allocated address

space.