IOCTL(2) BSD Programmer's Manual IOCTL(2)
ioctl - control device
ioctl(int d, unsigned long request, char *argp);
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.
An ioctl request has encoded in it whether the argument is an ``in'' pa-
rameter 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
If an error has occurred, a value of -1 is returned and errno is set to
indicate the error.
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 argp is not valid.
mt(1), execve(2), fcntl(2), tty(4), intro(4)
An ioctl function call appeared in Version 7 AT&T UNIX.
4th Berkeley Distribution December 11, 1993 1