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487 lines
16 KiB
Groff
487 lines
16 KiB
Groff
.\"
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.\" Devin Reade, January 1997
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.\"
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.\" $Id: tty.4,v 1.2 1998/04/16 05:03:39 gdr-ftp Exp $
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.\"
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.TH TTY 4 "15 April 1998" GNO Devices
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.SH NAME
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.BR tty
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\- general terminal interface
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.SH SYNOPSIS
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#include <sgtty.h>
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.SH DESCRIPTION
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This file documents the special file
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.BR .tty
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and the terminal drivers used for user-oriented I/O.
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.LP
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Terminals are controlled through calls to the
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.BR ioctl (2)
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system call:
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.nf
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#include <sgtty.h>
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ioctl(int \fIfiledes\fR, unsigned long \fIcode\fR, void *\fIarg\fR);
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.fi
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This is a very flexible interface where
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.I filedes
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specifies the terminal to modify,
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.I code
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indicates an action code, and
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.I arg
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is a pointer to a parameter block. The type of variable pointed to by
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.I arg
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and how it is interpreted depends on the value of
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.IR code.
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.LP
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Due to the colorful history of UNIX systems, the data structures used to
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manipulate terminal modes and settings are separated into five groups.
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Future revisions of GNO will implement the POSIX termio interface, which
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consolidates these structures into one place.
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.LP
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This manual page first explains the concepts of
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.IR "controlling terminals" ,
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.IR "process groups" ,
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and
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.IR "terminal modes" .
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It then goes on to explain each
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.I code
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that can be used with
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.BR ioctl (2)
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to control a terminal. Since there are five data structures used in
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.BR ioctl
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calls to control terminals, the description of the possible
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.IR code s
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in this man page is ordered by the type of the data structure pointed to by
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.IR arg .
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.IP "\fBThe Controlling Terminal\fR"
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Every process has associated with it a controlling terminal, which is
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the terminal from which the process was invoked. In some versions of
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UNIX, the controlling terminal association is responsible for job
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control; this is not so under GNO. A process' controlling terminal is
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inherited from its parent. By opening the special file
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.BR .tty ,
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a process can access its controlling terminal. This is useful where the
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input and output of a process was redirected and the process wants to
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be sure of getting input from or output to the user at the terminal.
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.sp 1
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A process can remove the association it has with its controlling terminal
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by opening the file
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.BR .tty
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and issuing the system call:
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.nf
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ioctl (\fIfd\fR, TIOCNOTTY, NULL);
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.fi
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where
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.IR fd
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is the file descriptor associated with
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.BR .tty .
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This is often desirable in server processes.
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.IP "\fBProcess Groups\fR"
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Every terminal has an associated process group. Any time a
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signal-generating special character is typed at the terminal, the
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terminal's process group is sent that signal. UNIX systems set process
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groups using
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.BR ioctl (2)
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calls, but under GNO a new interface method is used;
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process group assignments are controlled with the
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.BR JOBCONTROL (2)
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routines.
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.IP \fBModes\fR
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.\"
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.\" NOTE:
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.\"
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.\" The GNO v2.0.1 manual page listed four modes. The GNO v2.0.4
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.\" listed only three. I asked Jawaid about this, and he doesn't
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.\" recall what if any changes were made. What really needs to be
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.\" done is to have a kernel code review to see what the current
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.\" implementation does. In the interim, I have left (commented out)
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.\" the descriptions from the v2.0.1 manual page, below.
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.\" -- Devin Reade
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.\"
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.\" cooked mode
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.\"
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.\" On Unix systems, this mode also allows for input editing. It
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.\" is called cooked mode and is the normal state of the terminal driver.
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.\" Due to the history of the Apple II and it's operating systems, this
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.\" this precedent was not followed. Instead, to get input editing
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.\" features, use the ReadLine Toolbox call. Cooked-mode input editing
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.\" may be implemented for future releases of GNO.
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.\"
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.\" newline mode
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.\"
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.\" This mode is selected by using the GS/OS NewLine call. Input is
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.\" collected until one of the newline characters specified in the
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.\" NewLine call is encountered. At that point, the line of input is
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.\" returned, even if less than the number of bytes requested in the
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.\" Read call are read. I/O processing features are enabled and
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.\" disabled independently of newline mode; see cooked, cbreak, and raw.
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.\"
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.\" cbreak mode
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.\"
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.\" With GNO, this mode is the default state of the terminal driver,
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.\" and is synonymous with cooked mode. The requested number of
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.\" characters are read without regard to any newline setting; input
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.\" is not line buffered before being returned to the process.
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.\"
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.\" raw mode
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.\"
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.\" Like cbreak mode, except that no input or output processing whatsoever
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.\" is performed. The driver does not check for any special characters.
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.\"
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There are three modes in which terminal drivers operate. These modes
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control how the driver deals with I/O.
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.RS
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.IP \fIcooked\fR
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This is the default mode of the terminal driver. If an incoming character
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is one of the special characters defined in
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.BR sgttyb ,
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.BR tchars ,
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or
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.BR ltchars ,
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the appropriate action is performed (see below).
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This mode also allows for input editing, as input is internally buffered
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line by line, and data is returned to a reading process only when CR is
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entered.
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.IP \fIcbreak\fR
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Input is returned on a per-character basis, instead of line by line as in
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.I cooked
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mode. If no data is available, a read will block the calling process.
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If data is available, a number of characters up to but not exceeding the
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requested number will be returned. Special characters such as t_intrc are
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not handled, but are passed on to the caller as data.
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.IP \fIraw\fR
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Like
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.I cbreak
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mode, except that no input or output processing whatsoever is performed.
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.RE
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.IP "\fBstruct sgttyb\fR"
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The basic ioctls use the sgttyb structure:
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.nf
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struct sgttyb {
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char sg_ispeed;
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char sg_ospeed;
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char sg_erase;
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char sg_kill;
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short sg_flags;
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};
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.fi
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.RS
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.LP
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sg_ispeed and sg_ospeed indicate the baud rates for input and output
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according to the following table. Speed changes that do not apply to a
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particular piece of hardware are ignored (for instance, the console driver
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does not access a serial port so all baud rate settings are, in effect,
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impossible). Also, not all the baud rates supported by a particular
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device are allowed to be set from this interface.
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.LP
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These symbolic names for the baud rate settings are defined in <sgtty.h>.
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.RS
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.nf
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B0 0 (hang up dataphone)
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B50 1 50 baud
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B75 2 75 baud
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B110 3 110 baud
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B134 4 134.5 baud
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B150 5 150 baud
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B200 6 200 baud
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B300 7 300 baud
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B600 8 600 baud
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B1200 9 1200 baud
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B1800 10 1800 baud
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B2400 11 2400 baud
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B4800 12 4800 baud
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B9600 13 9600 baud
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B19200 14 19200 baud
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EXTA 14 19200 baud
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B38400 15 38400 baud
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EXTB 15 38400 baud
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.fi
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.RE
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The sg_erase and sg_kill fields specify the line-editing erase and kill
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characters. sg_erase is 0x7F (delete) by default, and sg_kill is not
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currently used.
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.LP
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sg_flags is a bitmapped value that indicates various state settings for
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the terminal driver (values are in hex).
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.nf
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EVENP 0x80 Use Even parity (serial devices only)
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ODDP 0x40 Use Odd parity (serial devices only)
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RAW 0x20 Raw mode: wake up on all characters,
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8-bit interface
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CRMOD 0x10 Map CR into LF; output LF as CR-LF
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ECHO 0x08 Echo (full duplex)
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CBREAK 0x02 Return each character as soon as typed
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TANDEM 0x01 Automatic flow control
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.fi
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.LP
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.B RAW
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and
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.B CBREAK
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modes were described above, in Modes.
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.LP
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If the
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.B CRMOD
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bit is set, a line feed character is appended to any emitted carriage return.
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.LP
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The
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.B ECHO
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bit controls input echoing; if enabled, any characters read from the terminal
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are echoed. This behavior differs slightly from UNIX, where input characters
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are echoed as soon as typed.
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.LP
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.B TANDEM
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mode enables automatic software flow control utilizing the special characters
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.B t_startc
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and
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.B t_stopc
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in tchars (below). Whenever the input queue is in danger of overflowing,
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the system sends t_stopc; when the queue has drained sufficiently, t_startc
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is sent. This mode has no effect on the console driver.
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.LP
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.IR Note :
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t_startc and t_stopc are used for both directions of flow control; when
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t_stopc is received from a remote system (or user), the terminal stops
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output, and when t_startc is received output resumes. Certain drivers
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may also require t_stopc and t_startc to be the same character, in which
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case one or the other setting will be ignored.
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See the driver's documentation for details.
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.LP
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The ioctl
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.IR code s
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that apply to sgtty are:
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.IP TIOCGETP
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Fetch the basic parameters associated with the terminal, and store in
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the sgttyb structure pointed to by
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.IR arg .
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.IP TIOCSETP
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Set the terminal's basic parameters according to the sgttyb structure
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pointed to by
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.IR arg .
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The input queue is flushed, and the call waits for the output queue to
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drain before the parameters are changed.
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.IP TIOCSETN
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This is like TIOCSETP, except there is no delay and the input queue is not
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flushed.
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.IP TIOCEXCL
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Set "exclusive-use" mode. The terminal may not be opened again by any
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process until all existing references are closed.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCNXCL
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Turns off "exclusive-use" mode.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCHPCL
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When the last reference to the terminal is closed, the terminal line is
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forced to hang up. This applies only to modem drivers.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCGETD
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The current line discipline number is stored in the int variable pointed to by
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.IR arg .
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This value is currently ignored.
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.IP TIOCSETD
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The line discipline is set to the value of the int pointed to by
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.IR arg .
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.IP TIOCFLUSH
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The specified queue is flushed. If the value pointed to by
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.I arg
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is zero, both the input and output queues are flushed. If the value is
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FREAD (defined in <sys/fcntl.h>), the input queue is flushed. If the value
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is FWRITE, the output queue is flushed.
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.IP TIOCSTI
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The character pointed to by
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.IR arg
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is placed in the input queue as if it had been typed on the terminal.
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.IP TIOCSBRK
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Begins a break sequence on the terminal.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCCBRK
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Ends a break sequence.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCSDTR
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The DTR line is turned on.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCCDTR
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The DTR line is turned off.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCSTOP
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Output is stopped as if t_stopc had been typed on the terminal.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCSTART
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If output is stopped, it is resumed as if t_startc had been typed on
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the terminal.
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.IR arg
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is ignored and should be the NULL pointer.
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.IP TIOCOUTQ
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The number of characters in the output queue is returned in the int
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pointed to by
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.IR arg .
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.IP FIONREAD
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The number of characters immediately available for input from the terminal
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is returned in the int pointed to by
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.IR arg .
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This is the preferred method of non-blocking I/O (checking for the presence
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of characters without waiting for them).
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.RE
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.IP "\fBstruct tchars\fR"
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The second structure associated with a terminal defines special
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characters. The structure is defined in <sys/ioctl.h> which is
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automatically included by <sgtty.h>:
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.RS
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.nf
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struct tchars {
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char t_intrc; /* interrupt */
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char t_quitc; /* quit */
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char t_startc; /* start output */
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char t_stopc; /* stop output */
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char t_eofc; /* end-of-file */
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char t_brkc; /* input delimiter (like nl) */
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};
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.fi
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The default values for these characters are ^C, ^\, ^Q, ^S, ^D and -1
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respectively. A value of -1 for any of the characters means that the
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effect of that character is ignored. The stop and start characters may
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be the same to produce a 'toggle' effect. It is not recommended to set
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any of the other characters to the same values; the order in which the
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special characters are checked is not defined, and the results you get
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may not be what was expected.
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.LP
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The ioctl calls that apply to tchars are:
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.IP TIOCGETC
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Returns the special characters settings in the tchars structure pointed to by
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.IR arg .
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.IP TIOCSETC
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The special characters are set according to tchars structure pointed to by
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.IR arg .
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.RE
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.IP "\fBLocal Mode\fR"
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The third "structure" in the terminal interface is a local mode word;
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.IR arg
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points to an int variable, which is broken up into bitfields.
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.\" From the GNO v2.0.1 man page:
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.\" None of the options are currently implemented for the console driver.
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.\" Other drivers may implement them; see the appropriate manpages for
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.\" details.
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The various bitfields in this word are as follows:
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.RS
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.LP
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.nf
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LCRTBS 0x0001 Backspace on erase rather than echoing erase
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LPRTERA 0x0002 Printing terminal erase mode
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LCRTERA 0x0004 Erase character echoes as backspace-space-backspace
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LTILDE 0x0008 Convert ~ to ` on output (for Hazeltine terminals)
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LMDMBUF 0x0010 Stop/start output when carrier drops
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LLITOUT 0x0020 Suppress output translations
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LTOSTOP 0x0040 Send SIGTTOU for background output (not implemented)
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LFLUSHO 0x0080 Output is being flushed
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LNOHANG 0x0100 Don't send hangup when carrier drops
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LPASSOUT 0x0200 Cooked mode with 8-bit output
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LCRTKIL 0x0400 BS-space-BS erase entire line on line kill
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LPASS8 0x0800 Pass all 8 bits through on input, in any mode
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LCTLECH 0x1000 Echo input control chars as ^?
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LPENDIN 0x2000 Retype pending input at next read or input character
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LDECCTQ 0x4000 Only ^Q restarts output after ^S
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LNOFLSH 0x8000 Inhibit flushing of pending I/O when intr char is typed
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.fi
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.LP
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The ioctl's used to access the local mode follow. In all cases
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.IR arg
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is a pointer to an int.
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.IP TIOCLBIS
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The bits of the local mode word specified by `1' bits in the argument are set;
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this operation is a bit-wise OR.
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.IP TIOCLBIC
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The bits of the local mode word specified by `1' bits in the argument are
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cleared; this operation ANDs the local mode with the bitwise negation of
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the argument.
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.IP TIOCLSET
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Sets the local mode word to the value of the argument.
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.IP TIOCLGET
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Returns the local mode word in the int pointed to by arg.
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.RE
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.IP "\fBstruct ltchars\fR"
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The fourth terminal structure is another set of special
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characters. The structure is named ltchars (for Local Special Characters)
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and is again defined in <ioctl.h>.
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.RS
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.nf
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struct ltchars {
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char t_suspc; /* stop process signal */
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char t_dsuspc; /* delayed stop process signal */
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char t_rprntc; /* reprint line */
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char t_flushc; /* flush output (toggles) */
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char t_werasc; /* word erase */
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char t_lnextc; /* literal next character */
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};
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.fi
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Defaults for these characters are ^Z, ^Y, ^R, ^O, ^W, and ^V.
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As with tchars, a value of -1 disables the effect of that character.
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Only t_suspc is currently implemented for the console driver.
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.LP
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The applicable ioctl functions are:
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.IP TIOCSLTC
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sets the local characters according to the ltchars structure pointed to by
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.IR arg .
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.IP TIOCGLTC
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retreives the local characters, storing them in the ltchars structure
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pointed to by
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.IR arg .
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.RE
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.IP "\fBstruct winsize\fR"
|
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The fifth structure associated with terminals is the winsize struct.
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Provision is made in the kernel for storage of the current window or terminal
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size along with the other terminal information. This info is
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recorded in a winsize structure, and is defined in <ioctl.h>:
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.RS
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.LP
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.nf
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struct winsize {
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unsigned short ws_row; /* rows, in characters */
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unsigned short ws_col; /* columns, in characters */
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unsigned short ws_xpixel; /* horizontal size, pixels */
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unsigned short ws_ypixel; /* vertical size, pixels */
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};
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.fi
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.LP
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A '0' in a field indicates that the field value is undefined. '0' is
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the default when a terminal is first opened. These values are not used
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by the terminal driver itself; rather, they are for the benefit of
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applications. The ioctl calls for winsize are:
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.IP TIOCGWINSZ
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Returns the window size parameters in the provided winsize structure.
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.IP TIOCSWINSZ
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Sets the window size parameters. If any of the values differ from the
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old ones, a SIGWINCH signal is sent to the terminal's process group.
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.RE
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.SH FILES
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.BR ".tty"
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.br
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.BR ".ttyco" " (console driver)"
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.br
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.BR ".tty*" " (user-installed drivers)"
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.SH "SEE ALSO"
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.IR "GNO Shell Reference Manual" ,
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.BR stty (1),
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.BR ioctl(2),
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.BR signal(2)
|