ct -- Device Driver

Controlling terminal driver

Most  processes that  the COHERENT  kernel executes  are associated  with a
controlling terminal.  (The only exceptions  are daemon processes  that are
started by  the process  init.) This terminal  directs I/O to  the physical
device  through  which  the  user  who  invoked the  process  is  accessing
COHERENT.  Usually, this is a serial port or the console, but it could also
be a socket (in the case of a telnet or ftp session), or some other device.

The driver ct lets a program access the controlling terminal automatically.
It is  accessed through the  device /dev/tty. Thus, when  a program invokes
the system calls open(),  close(), ioctl(), read(), or write() on /dev/tty,
driver ct  directs those calls automatically to  the appropriate driver for
the controlling terminal.  This spares applications from having to know the
details  of the  controlling  device --  all  it has  to  do is  manipulate
/dev/tty and let ct take care of the details.

Files

/dev/tty

See Also

device drivers,
init

Diagnostics

When a call finds no valid controlling terminal for a process, it returns a
value of -1 and sets errno to ENXIO.

© 2012 by Stephen A. Ness