e18651243e
While I didn't plan another upgrade, This version incorporate fixes from kevans@ so let's upgrade to it
164 lines
6.1 KiB
Groff
164 lines
6.1 KiB
Groff
.\"***************************************************************************
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.\" Copyright 2018,2020 Thomas E. Dickey *
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.\" Copyright 1998-2016,2017 Free Software Foundation, Inc. *
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.\" *
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.\" Permission is hereby granted, free of charge, to any person obtaining a *
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.\" copy of this software and associated documentation files (the *
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.\" "Software"), to deal in the Software without restriction, including *
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.\" without limitation the rights to use, copy, modify, merge, publish, *
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.\" distribute, distribute with modifications, sublicense, and/or sell *
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.\" copies of the Software, and to permit persons to whom the Software is *
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.\" furnished to do so, subject to the following conditions: *
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.\" *
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.\" The above copyright notice and this permission notice shall be included *
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.\" in all copies or substantial portions of the Software. *
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.\" *
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
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.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
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.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
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.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
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.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
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.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
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.\" *
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.\" Except as contained in this notice, the name(s) of the above copyright *
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.\" holders shall not be used in advertising or otherwise to promote the *
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.\" sale, use or other dealings in this Software without prior written *
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.\" authorization. *
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.\"***************************************************************************
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.\"
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.\" $Id: clear.1,v 1.23 2020/02/02 23:34:34 tom Exp $
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.TH @CLEAR@ 1 ""
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.\" these would be fallbacks for DS/DE,
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.\" but groff changed the meaning of the macros.
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.de NS
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.ie n .sp
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.el .sp .5
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.ie n .in +4
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.el .in +2
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.nf
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.ft C \" Courier
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..
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.de NE
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.fi
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.ft R
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.ie n .in -4
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.el .in -2
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..
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.ie \n(.g .ds `` \(lq
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.el .ds `` ``
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.ie \n(.g .ds '' \(rq
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.el .ds '' ''
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.de bP
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.ie n .IP \(bu 4
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.el .IP \(bu 2
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..
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.ds n 5
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.SH NAME
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\fB@CLEAR@\fR \- clear the terminal screen
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.SH SYNOPSIS
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\fB@CLEAR@\fR [\fB\-T\fR\fItype\fR] [\fB\-V\fP] [\fB\-x\fP]
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.br
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.SH DESCRIPTION
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\fB@CLEAR@\fR clears your screen if this is possible,
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including its scrollback buffer
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(if the extended \*(``E3\*('' capability is defined).
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\fB@CLEAR@\fR looks in the environment for the terminal type
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given by the environment variable \fBTERM\fP,
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and then in the
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\fBterminfo\fR database to determine how to clear the screen.
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.PP
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\fB@CLEAR@\fR writes to the standard output.
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You can redirect the standard output to a file (which prevents
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\fB@CLEAR@\fR from actually clearing the screen),
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and later \fBcat\fP the file to the screen, clearing it at that point.
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.SH OPTIONS
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.PP
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.TP 5
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.B \-T \fItype\fP
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indicates the \fItype\fR of terminal.
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Normally this option is
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unnecessary, because the default is taken from the environment
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variable \fBTERM\fR.
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If \fB\-T\fR is specified, then the shell
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variables \fBLINES\fR and \fBCOLUMNS\fR will also be ignored.
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.TP
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.B \-V
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reports the version of ncurses which was used in this program, and exits.
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The options are as follows:
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.TP
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.B \-x
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do not attempt to clear the terminal's scrollback buffer
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using the extended \*(``E3\*('' capability.
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.SH HISTORY
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A \fBclear\fP command appeared in 2.79BSD dated February 24, 1979.
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Later that was provided in Unix 8th edition (1985).
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.PP
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AT&T adapted a different BSD program (\fBtset\fP) to make
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a new command (\fBtput\fP),
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and used this to replace the \fBclear\fP command with a shell script
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which calls \fBtput clear\fP, e.g.,
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.NS
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/usr/bin/tput ${1:+-T$1} clear 2> /dev/null
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exit
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.NE
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.PP
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In 1989, when Keith Bostic revised the BSD \fBtput\fP command
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to make it similar to the AT&T \fBtput\fP,
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he added a shell script for the \fBclear\fP command:
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.NS
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exec tput clear
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.NE
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.PP
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The remainder of the script in each case is a copyright notice.
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.PP
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The ncurses \fBclear\fP command began in 1995 by adapting the original
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BSD \fBclear\fP command (with terminfo, of course).
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.PP
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The \fBE3\fP extension came later:
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.bP
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In June 1999, xterm provided an extension to the standard control
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sequence for clearing the screen.
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Rather than clearing just the visible part of the screen using
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.NS
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printf '\\033[2J'
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.NE
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.IP
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one could clear the \fIscrollback\fP using
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.NS
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printf '\\033[\fB3\fPJ'
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.NE
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.IP
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This is documented in \fIXTerm Control Sequences\fP as a feature originating
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with xterm.
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.bP
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A few other terminal developers adopted the feature, e.g., PuTTY in 2006.
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.bP
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In April 2011, a Red Hat developer submitted a patch to the Linux
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kernel, modifying its console driver to do the same thing.
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The Linux change, part of the 3.0 release, did not mention xterm,
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although it was cited in the Red Hat bug report (#683733)
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which led to the change.
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.bP
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Again, a few other terminal developers adopted the feature.
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But the
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next relevant step was a change to the \fBclear\fP program in 2013
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to incorporate this extension.
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.bP
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In 2013, the \fBE3\fP extension was overlooked in \fB@TPUT@\fP with
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the \*(``clear\*('' parameter.
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That was addressed in 2016 by reorganizing \fB@TPUT@\fP to share
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its logic with \fB@CLEAR@\fP and \fB@TSET@\fP.
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.SH PORTABILITY
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Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
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(POSIX.1-2008) nor X/Open Curses Issue 7 documents @TSET@ or @RESET@.
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.PP
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The latter documents \fBtput\fP, which could be used to replace this utility
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either via a shell script or by an alias (such as a symbolic link) to
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run \fB@TPUT@\fP as \fB@CLEAR@\fP.
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.SH SEE ALSO
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\fB@TPUT@\fR(1), \fBterminfo\fR(\*n)
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.PP
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This describes \fBncurses\fR
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version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@).
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