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175 lines
6.9 KiB
Perl
175 lines
6.9 KiB
Perl
.\" Copyright (c) 1983, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)2.4.t 8.1 (Berkeley) 6/8/93
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.\"
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.sh "Terminals and Devices
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.NH 3
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Terminals
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.PP
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Terminals support \fIread\fP and \fIwrite\fP I/O operations,
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as well as a collection of terminal specific \fIioctl\fP operations,
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to control input character interpretation and editing,
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and output format and delays.
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.NH 4
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Terminal input
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.PP
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Terminals are handled according to the underlying communication
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characteristics such as baud rate and required delays,
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and a set of software parameters.
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.NH 5
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Input modes
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.PP
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A terminal is in one of three possible modes: \fIraw\fP, \fIcbreak\fP,
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or \fIcooked\fP.
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In raw mode all input is passed through to the
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reading process immediately and without interpretation.
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In cbreak mode, the handler interprets input only by looking
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for characters that cause interrupts or output flow control;
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all other characters are made available as in raw mode.
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In cooked mode, input
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is processed to provide standard line-oriented local editing functions,
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and input is presented on a line-by-line basis.
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.NH 5
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Interrupt characters
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.PP
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Interrupt characters are interpreted by the terminal handler only in
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cbreak and cooked modes, and
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cause a software interrupt to be sent to all processes in the process
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group associated with the terminal. Interrupt characters exist
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to send SIGINT
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and SIGQUIT signals,
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and to stop a process group
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with the SIGTSTP signal either immediately, or when
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all input up to the stop character has been read.
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.NH 5
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Line editing
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.PP
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When the terminal is in cooked mode, editing of an input line
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is performed. Editing facilities allow deletion of the previous
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character or word, or deletion of the current input line.
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In addition, a special character may be used to reprint the current
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input line after some number of editing operations have been applied.
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.PP
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Certain other characters are interpreted specially when a process is
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in cooked mode. The \fIend of line\fP character determines
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the end of an input record. The \fIend of file\fP character simulates
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an end of file occurrence on terminal input. Flow control is provided
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by \fIstop output\fP and \fIstart output\fP control characters. Output
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may be flushed with the \fIflush output\fP character; and a \fIliteral
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character\fP may be used to force literal input of the immediately
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following character in the input line.
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.PP
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Input characters may be echoed to the terminal as they are received.
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Non-graphic ASCII input characters may be echoed as a two-character
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printable representation, ``^character.''
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.NH 4
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Terminal output
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.PP
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On output, the terminal handler provides some simple formatting services.
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These include converting the carriage return character to the
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two character return-linefeed sequence,
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inserting delays after certain standard control characters,
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expanding tabs, and providing translations
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for upper-case only terminals.
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.NH 4
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Terminal control operations
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.PP
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When a terminal is first opened it is initialized to a standard
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state and configured with a set of standard control, editing,
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and interrupt characters. A process
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may alter this configuration with certain
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control operations, specifying parameters in a standard structure:\(dg
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.FS
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\(dg The control interface described here is an internal interface only
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in 4.3BSD. Future releases will probably use a modified interface
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based on currently-proposed standards.
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.FE
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.DS
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._f
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struct ttymode {
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short tt_ispeed; /* input speed */
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int tt_iflags; /* input flags */
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short tt_ospeed; /* output speed */
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int tt_oflags; /* output flags */
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};
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.DE
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and ``special characters'' are specified with the
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\fIttychars\fP structure,
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.DS
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._f
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struct ttychars {
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char tc_erasec; /* erase char */
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char tc_killc; /* erase line */
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char tc_intrc; /* interrupt */
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char tc_quitc; /* quit */
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char tc_startc; /* start output */
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char tc_stopc; /* stop output */
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char tc_eofc; /* end-of-file */
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char tc_brkc; /* input delimiter (like nl) */
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char tc_suspc; /* stop process signal */
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char tc_dsuspc; /* delayed stop process signal */
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char tc_rprntc; /* reprint line */
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char tc_flushc; /* flush output (toggles) */
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char tc_werasc; /* word erase */
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char tc_lnextc; /* literal next character */
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};
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.DE
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.NH 4
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Terminal hardware support
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.PP
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The terminal handler allows a user to access basic
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hardware related functions; e.g. line speed,
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modem control, parity, and stop bits. A special signal,
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SIGHUP, is automatically
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sent to processes in a terminal's process
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group when a carrier transition is detected. This is
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normally associated with a user hanging up on a modem
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controlled terminal line.
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.NH 3
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Structured devices
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.PP
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Structures devices are typified by disks and magnetic
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tapes, but may represent any random-access device.
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The system performs read-modify-write type buffering actions on block
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devices to allow them to be read and written in a totally random
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access fashion like ordinary files.
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File systems are normally created in block devices.
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.NH 3
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Unstructured devices
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.PP
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Unstructured devices are those devices which
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do not support block structure. Familiar unstructured devices
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are raw communications lines (with
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no terminal handler), raster plotters, magnetic tape and disks unfettered
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by buffering and permitting large block input/output and positioning
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and formatting commands.
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