.TH IOCTL 2
.CT 2 file_io file_inq_creat
.SH NAME
ioctl \(mi miscellaneous control operations
.SH SYNOPSIS
.nf
.B #include <sgtty.h>
.PP
.B int ioctl(fildes, request, argp)
.B struct sgttyb *argp;
.fi
.SH DESCRIPTION
.I Ioctl
performs a variety of functions
on special files and streams.
The writeups of various devices
in section 4 discuss how
.I ioctl
applies to them.
.PP
Some calls, however, apply to any open file,
including
the process-exclusive calls
.BR FIOPX,
.BR FIONPX,
and
.BR FIOQX
(see
.IR pex (4)),
as well as
the following two standard calls,
.IP
.L
ioctl(fildes, FIOCLEX, (void *)0);
.br
.L
ioctl(fildes, FIONCLEX, (void *)0);
.LP
The first causes the file to be closed automatically upon
a successful
.IR exec (2);
the second causes the file to be left open.
.SH "SEE ALSO"
.IR stty (1), 
.IR exec (2),
.IR proc (4),
.IR ttyld (4)
.SH DIAGNOSTICS
.BR EBADF ,
.BR EFAULT ,
.BR EIO ,
.BR ELAB ,
.BR ENODEV ,
.BR ENOTTY
.SH BUGS
Strictly speaking,
since
.I ioctl
may be extended in different ways to devices with
different properties,
.I argp
should have an open-ended declaration like
.IP
.L
union { struct sgttyb ...; ... } *argp;
.PP
The important thing is that the size is at least
.B sizeof(struct
.BR sgttyb) .
.br
.I Ioctl
requests vary among UNIX systems;
undisciplined use is likely to compromise portability.