|IOCTL(2)||System Calls Manual||IOCTL(2)|
ioctl — control
d, unsigned long
function manipulates the underlying device parameters of special files. In
particular, many operating characteristics of character special files (e.g.,
terminals) may be controlled with
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.
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
Some ioctls are applicable to any file descriptor. These include:
Some generic ioctls are not implemented for all types of file descriptors. These include:
EAGAINimmediately when no data is available.
FIOSETOWNwill start receiving
SIGIOsignals when data is available. The
SIGIOsignal will be delivered when data is available on the file descriptor.
FIOSETOWN, FIOGETOWNint *
SIGIOsignals when data is available.
If an error has occurred, a value of -1 is returned and errno is set to indicate the error.
ioctl() will fail if:
ioctl() function call appeared in
Version 7 AT&T UNIX.
|August 11, 2019||OpenBSD-current|