.TH FT 4 
.UC
.SH NAME
ft \- fake interval timer
.SH DESCRIPTION
.I Ft
is a pseudo-device that makes it possible to simulate an
.IR alarm (2)
call with better than 1 second resolution.
.PP
To use the interval timer, open one of the files
.I /dev/ft?.
This opens the interval timer for exclusive use;
an attempt by another process to open the timer will fail
with error indication EBUSY in 
.I errno
\- see
.IR intro (2).
The resulting file descriptor can be the argument of an
.IR ioctl (2)
call:
.RS 1
.nf

 #include <sgtty.h>

struct	requestbuf {
	short	time;
	short	signo;
 } request;

 ioctl(fildes, FTIOCSET, (struct sgttyb *) &request);

.fi
.RE
After
.I time
clock cycles (fiftieths or sixtieths of a second),
a signal of type
.I signo
will be sent to the requesting process.
The requested
.I time
may not exceed 60 seconds
(if longer delays are required the real
.IR alarm (2)
call should be used).
The
.IR ioctl (2)
call
.RS 1

 ioctl(fildes, FTIOCCANCEL, (struct sgttyb *) NULL);

.RE
cancels any outstanding interrupt request.
.SH FILES
/dev/ft?
.SH "SEE ALSO"
alarm(2), ioctl(2)
.SH BUGS
An FTIOCCANCEL request prevents the signal from being sent
when the interval has expired, but does not actually cancel
the timeout request.
It cannot be followed by a new FTIOCSET request
until the original delay has expired.