HP-UX Reference (11i v1 05/09) - 5 Miscellaneous Topics (vol 9)

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ioctl(5) ioctl(5)

NAME

ioctl - generic device control commands

SYNOPSIS

#include <sys/ioctl.h>

ioctl(fildes, request, arg)

int fildes, request;

DESCRIPTION

The ioctl(2) system call provides for control over open devices. This include ﬁle describes requests and

arguments used in ioctl(2) which are of a generic nature. For details about how individual requests will

affect any particular device, see the corresponding device manual entry in Section (7). If a device does not

support an ioctl request it returns

EINVAL.

FIONREAD

Returns in the long integer whose address is arg the number of characters immediately readable

from the device ﬁle.

FIOSSAIOSTAT

For those character device ﬁles which support this command, if the integer whose address is arg is

non-zero, system asynchronous

I/O is enabled; that is, enable SIGIO to be sent to the process

currently designated with FIOSSAIOOWN (see below) whenever device-ﬁle-dependent events occur.

If no process has been designated with FIOSSAIOOWN, then enable SIGIO to be sent to the ﬁrst pro-

cess to open the device ﬁle.

If the designated process has exited, the SIGIO signal is not sent to any process.

If the integer whose address is arg is 0, system asynchronous I/O is disabled.

FIOGSAIOSTAT

For those character device ﬁles which support this command, the integer whose address is arg is

set to 1, if system asynchronous

I/O is enabled. Otherwise, the integer whose address is arg is set

to 0.

FIOSSAIOOWN

For those character device ﬁles which support this command, set process ID to receive the

SIGIO

signals with system asynchronous I/O to the value of the integer whose address is arg. Users with

appropriate privileges can designate that any process receive the

SIGIO signals. If the request is

not made by the super-user, only the calling process is allowed to designate that itself or another

process whose real or saved effective user ID matches its real or effective user

ID, or a process

which is a descendant of the calling process, receive the

SIGIO signals. If no process can be found

corresponding to that speciﬁed by the integer whose address is arg, the call will fail, with errno

set to

ESRCH. If the request is not made by the super-user and the calling process attempts to

designate a process other than itself or (1) another process whose real or saved effective user

matches its real or effective user ID, or (2) a process which is not a descendant of the calling pro-

cess, the call fails, with errno set to EPERM.

If the designated process subsequently exits, the SIGIO signal will not be sent to any process.

The default when opening a device ﬁle is that the process performing the open is set to receive the

SIGIO signals.

FIOGSAIOOWN

For those character device ﬁles which support this command, the integer whose address is arg is

set to the process ID designated to receive SIGIO signals.

FIOSNBIO

For those character device ﬁles which support this command, if the integer whose address is arg is

non-zero, non-blocking I/O is enabled; that is, subsequent reads and writes to the device ﬁle are

handled in a non-blocking manner (see below). If the integer whose address is arg is 0, non-

blocking I/O is disabled.

For reads, non-blocking I/O prevents all read requests to that device from blocking, whether the

requests succeed or fail. Such read requests complete in one of three ways:

• If there is enough data available to satisfy the entire request, the read completes success-

fully, having read all of the data, and returns the number of bytes read;

HP-UX 11i Version 1: September 2005 − 1 − Hewlett-Packard Company Section 5−−73