Provided by: freebsd-manpages_8.2-1_all bug

NAME

     tty — general terminal interface

SYNOPSIS

     #include <sys/ioctl.h>

DESCRIPTION

     This section describes the interface to the terminal drivers in the system.

   Terminal Special Files
     Each hardware terminal port on the system usually has a terminal special device file
     associated with it in the directory ``/dev/'' (for example, ``/dev/tty03'').  When a user
     logs into the system on one of these hardware terminal ports, the system has already opened
     the associated device and prepared the line for normal interactive use (see getty(8).)
     There is also a special case of a terminal file that connects not to a hardware terminal
     port, but to another program on the other side.  These special terminal devices are called
     ptys and provide the mechanism necessary to give users the same interface to the system when
     logging in over a network (using rlogin(1), or telnet(1) for example).  Even in these cases
     the details of how the terminal file was opened and set up is already handled by special
     software in the system.  Thus, users do not normally need to worry about the details of how
     these lines are opened or used.  Also, these lines are often used for dialing out of a
     system (through an out-calling modem), but again the system provides programs that hide the
     details of accessing these terminal special files (see tip(1)).

     When an interactive user logs in, the system prepares the line to behave in a certain way
     (called a line discipline), the particular details of which is described in stty(1) at the
     command level, and in termios(4) at the programming level.  A user may be concerned with
     changing settings associated with his particular login terminal and should refer to the
     preceding man pages for the common cases.  The remainder of this man page is concerned with
     describing details of using and controlling terminal devices at a low level, such as that
     possibly required by a program wishing to provide features similar to those provided by the
     system.

   Terminal File Operations
     All of the following operations are invoked using the ioctl(2) system call.  Refer to that
     man page for a description of the request and argp parameters.  In addition to the ioctl
     requests defined here, the specific line discipline in effect will define other requests
     specific to it (actually termios(4) defines them as function calls, not ioctl requests.)
     The following section lists the available ioctl requests.  The name of the request, a
     description of its purpose, and the typed argp parameter (if any) are listed.  For example,
     the first entry says

           TIOCSPGRP int *tpgrp

     and would be called on the terminal associated with file descriptor zero by the following
     code fragment:

             int pgrp;

             pgrp = getpgrp();
             ioctl(0, TIOCSPGRP, &pgrp);

   Terminal File Request Descriptions
     TIOCSETD int *ldisc
                 This call is obsolete but left for compatibility.  Before FreeBSD 8.0, it would
                 change to the new line discipline pointed to by ldisc.

     TIOCGETD int *ldisc
                 Return the current line discipline in the integer pointed to by ldisc.

     TIOCSBRK void
                 Set the terminal hardware into BREAK condition.

     TIOCCBRK void
                 Clear the terminal hardware BREAK condition.

     TIOCSDTR void
                 Assert data terminal ready (DTR).

     TIOCCDTR void
                 Clear data terminal ready (DTR).

     TIOCGPGRP int *tpgrp
                 Return the current process group with which the terminal is associated in the
                 integer pointed to by tpgrp.  This is the underlying call that implements the
                 termios(4) tcgetattr() call.

     TIOCSPGRP int *tpgrp
                 Associate the terminal with the process group (as an integer) pointed to by
                 tpgrp.  This is the underlying call that implements the termios(4) tcsetattr()
                 call.

     TIOCGETA struct termios *term
                 Place the current value of the termios state associated with the device in the
                 termios structure pointed to by term.  This is the underlying call that
                 implements the termios(4) tcgetattr() call.

     TIOCSETA struct termios *term
                 Set the termios state associated with the device immediately.  This is the
                 underlying call that implements the termios(4) tcsetattr() call with the TCSANOW
                 option.

     TIOCSETAW struct termios *term
                 First wait for any output to complete, then set the termios state associated
                 with the device.  This is the underlying call that implements the termios(4)
                 tcsetattr() call with the TCSADRAIN option.

     TIOCSETAF struct termios *term
                 First wait for any output to complete, clear any pending input, then set the
                 termios state associated with the device.  This is the underlying call that
                 implements the termios(4) tcsetattr() call with the TCSAFLUSH option.

     TIOCOUTQ int *num
                 Place the current number of characters in the output queue in the integer
                 pointed to by num.

     TIOCSTI char *cp
                 Simulate typed input.  Pretend as if the terminal received the character pointed
                 to by cp.

     TIOCNOTTY void
                 This call is obsolete but left for compatibility.  In the past, when a process
                 that did not have a controlling terminal (see The Controlling Terminal in
                 termios(4)) first opened a terminal device, it acquired that terminal as its
                 controlling terminal.  For some programs this was a hazard as they did not want
                 a controlling terminal in the first place, and this provided a mechanism to
                 disassociate the controlling terminal from the calling process.  It must be
                 called by opening the file /dev/tty and calling TIOCNOTTY on that file
                 descriptor.

                 The current system does not allocate a controlling terminal to a process on an
                 open() call: there is a specific ioctl called TIOCSCTTY to make a terminal the
                 controlling terminal.  In addition, a program can fork() and call the setsid()
                 system call which will place the process into its own session - which has the
                 effect of disassociating it from the controlling terminal.  This is the new and
                 preferred method for programs to lose their controlling terminal.

     TIOCSTOP void
                 Stop output on the terminal (like typing ^S at the keyboard).

     TIOCSTART void
                 Start output on the terminal (like typing ^Q at the keyboard).

     TIOCSCTTY void
                 Make the terminal the controlling terminal for the process (the process must not
                 currently have a controlling terminal).

     TIOCDRAIN void
                 Wait until all output is drained.

     TIOCEXCL void
                 Set exclusive use on the terminal.  No further opens are permitted except by
                 root.  Of course, this means that programs that are run by root (or setuid) will
                 not obey the exclusive setting - which limits the usefulness of this feature.

     TIOCNXCL void
                 Clear exclusive use of the terminal.  Further opens are permitted.

     TIOCFLUSH int *what
                 If the value of the int pointed to by what contains the FREAD bit as defined in
                 <sys/file.h>, then all characters in the input queue are cleared.  If it
                 contains the FWRITE bit, then all characters in the output queue are cleared.
                 If the value of the integer is zero, then it behaves as if both the FREAD and
                 FWRITE bits were set (i.e., clears both queues).

     TIOCGWINSZ struct winsize *ws
                 Put the window size information associated with the terminal in the winsize
                 structure pointed to by ws.  The window size structure contains the number of
                 rows and columns (and pixels if appropriate) of the devices attached to the
                 terminal.  It is set by user software and is the means by which most full-screen
                 oriented programs determine the screen size.  The winsize structure is defined
                 in <sys/ioctl.h>.

     TIOCSWINSZ struct winsize *ws
                 Set the window size associated with the terminal to be the value in the winsize
                 structure pointed to by ws (see above).

     TIOCCONS int *on
                 If on points to a non-zero integer, redirect kernel console output (kernel
                 printf's) to this terminal.  If on points to a zero integer, redirect kernel
                 console output back to the normal console.  This is usually used on workstations
                 to redirect kernel messages to a particular window.

     TIOCMSET int *state
                 The integer pointed to by state contains bits that correspond to modem state.
                 Following is a list of defined variables and the modem state they represent:

                 TIOCM_LE   Line Enable.
                 TIOCM_DTR  Data Terminal Ready.
                 TIOCM_RTS  Request To Send.
                 TIOCM_ST   Secondary Transmit.
                 TIOCM_SR   Secondary Receive.
                 TIOCM_CTS  Clear To Send.
                 TIOCM_CAR  Carrier Detect.
                 TIOCM_CD   Carrier Detect (synonym).
                 TIOCM_RNG  Ring Indication.
                 TIOCM_RI   Ring Indication (synonym).
                 TIOCM_DSR  Data Set Ready.

                 This call sets the terminal modem state to that represented by state.  Not all
                 terminals may support this.

     TIOCMGET int *state
                 Return the current state of the terminal modem lines as represented above in the
                 integer pointed to by state.

     TIOCMBIS int *state
                 The bits in the integer pointed to by state represent modem state as described
                 above, however the state is OR-ed in with the current state.

     TIOCMBIC int *state
                 The bits in the integer pointed to by state represent modem state as described
                 above, however each bit which is on in state is cleared in the terminal.

IMPLEMENTATION NOTES

     The total number of input and output bytes through all terminal devices are available via
     the kern.tk_nin and kern.tk_nout read-only sysctl(8) variables.

SEE ALSO

     stty(1), ioctl(2), ng_tty(4), pty(4), termios(4), getty(8)