IOCTL(2) BSD System Calls Manual IOCTL(2)NAMEioctl — control device
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/ioctl.h>
int
ioctl(int d, unsigned long request, ...);
DESCRIPTION
The ioctl() system call manipulates the underlying device parameters of
special files. In particular, many operating characteristics of charac‐
ter special files (e.g. terminals) may be controlled with ioctl()
requests. The argument d must be an open file descriptor.
The third argument to ioctl() is traditionally named char *argp. Most
uses of ioctl() however, require the third argument to be a caddr_t or an
int.
An ioctl() request has encoded in it whether the argument is an “in”
argument or “out” argument, 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 VALUES
If an error has occurred, a value of -1 is returned and errno is set to
indicate the error.
ERRORSIoctl() 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.
[EFAULT] argp points outside the process's allocated address
space.
SEE ALSOexecve(2), fcntl(2), intro(4), tty(4), ioctl(9)HISTORY
An ioctl() function call appeared in Version 7 AT&T UNIX.
BSD December 11, 1993 BSD
