mirror of
https://github.com/Aigor44/ncursesw-morphos.git
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ce4803687b
+ fix several formatting issues with manual pages. + correct read of terminfo entry in which all strings are absent or explicitly cancelled. Before this fix, the result was that all were treated as only absent. + modify infocmp to suppress mixture of absent/cancelled capabilities that would only show as "NULL, NULL", unless the -q option is used, e.g., to show "-, @" or "@, -".
168 lines
7.8 KiB
HTML
168 lines
7.8 KiB
HTML
<!--
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****************************************************************************
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* Copyright (c) 1998-2013,2016 Free Software Foundation, Inc. *
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* Permission is hereby granted, free of charge, to any person obtaining a *
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* The above copyright notice and this permission notice shall be included *
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****************************************************************************
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* @Id: clear.1,v 1.16 2016/12/31 16:09:34 tom Exp @
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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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-->
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
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<HTML>
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<HEAD>
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<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
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<meta name="generator" content="Manpage converted by man2html - see http://invisible-island.net/scripts/readme.html#others_scripts">
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<TITLE>clear 1</TITLE>
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<link rev=made href="mailto:bug-ncurses@gnu.org">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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</HEAD>
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<BODY>
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<H1 class="no-header">clear 1</H1>
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<PRE>
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<STRONG><A HREF="clear.1.html">clear(1)</A></STRONG> <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
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</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
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<STRONG>clear</STRONG> - clear the terminal screen
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</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
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<STRONG>clear</STRONG>
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</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
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<STRONG>clear</STRONG> clears your screen if this is possible, including
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its scrollback buffer (if the extended "E3" capability is
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defined). <STRONG>clear</STRONG> looks in the environment for the terminal
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type given by the environment variable <STRONG>TERM</STRONG>, and then in
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the <STRONG>terminfo</STRONG> database to determine how to clear the
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screen.
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<STRONG>clear</STRONG> writes to the standard output. You can redirect the
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standard output to a file (which prevents <STRONG>clear</STRONG> from actu-
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ally clearing the screen), and later <STRONG>cat</STRONG> the file to the
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screen, clearing it at that point.
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<STRONG>clear</STRONG> ignores any command-line parameters that may be
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present. The analogous "<STRONG>tput</STRONG> clear" has command-line
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parameters including <STRONG>-T</STRONG> for overriding the <STRONG>TERM</STRONG> environ-
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ment variable.
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</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
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A <STRONG>clear</STRONG> command appeared in 2.79BSD dated February 24,
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1979. Later that was provided in Unix 8th edition (1985).
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AT&T adapted a different BSD program (<STRONG>tset</STRONG>) to make a new
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command (<STRONG>tput</STRONG>), and used this to replace the <STRONG>clear</STRONG> command
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with a shell script which calls <STRONG>tput</STRONG> <STRONG>clear</STRONG>, e.g.,
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/usr/bin/tput ${1:+-T$1} clear 2> /dev/null
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exit
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In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to
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make it similar to the AT&T <STRONG>tput</STRONG>, he added a shell script
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for the <STRONG>clear</STRONG> command:
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exec tput clear
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The remainder of the script in each case is a copyright
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notice.
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The ncurses <STRONG>clear</STRONG> command began in 1995 by adapting the
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original BSD <STRONG>clear</STRONG> command (with terminfo, of course).
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The <STRONG>E3</STRONG> extension came later:
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<STRONG>o</STRONG> In June 1999, xterm provided an extension to the stan-
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dard control sequence for clearing the screen. Rather
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than clearing just the visible part of the screen
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using
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printf '\033[2J'
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one could clear the <EM>scrollback</EM> using
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printf '\033[<STRONG>3</STRONG>J'
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This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a
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feature originating with xterm.
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<STRONG>o</STRONG> A few other terminal developers adopted the feature,
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e.g., PuTTY in 2006.
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<STRONG>o</STRONG> In April 2011, a Red Hat developer submitted a patch
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to the Linux kernel, modifying its console driver to
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do the same thing. The Linux change, part of the 3.0
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release, did not mention xterm, although it was cited
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in the Red Hat bug report (#683733) which led to the
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change.
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<STRONG>o</STRONG> Again, a few other terminal developers adopted the
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feature. But the next relevant step was a change to
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the <STRONG>clear</STRONG> program in 2013 to incorporate this exten-
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sion.
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<STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> extension was overlooked in <STRONG>tput</STRONG> with
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the "clear" parameter. That was addressed in 2016 by
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reorganizing <STRONG>tput</STRONG> to share its logic with <STRONG>clear</STRONG> and
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<STRONG>tset</STRONG>.
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</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
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Neither IEEE Std 1003.1/The Open Group Base Specifica-
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tions Issue 7 (POSIX.1-2008) nor X/Open Curses Issue 7
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documents tset or reset.
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The latter documents <STRONG>tput</STRONG>, which could be used to replace
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this utility either via a shell script or by an alias
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(such as a symbolic link) to run <STRONG>tput</STRONG> as <STRONG>clear</STRONG>.
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</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
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<STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
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This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20170218).
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<STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
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</PRE>
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<div class="nav">
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<ul>
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<li><a href="#h2-NAME">NAME</a></li>
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<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
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<li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
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<li><a href="#h2-HISTORY">HISTORY</a></li>
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<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
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<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
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</ul>
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</div>
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</BODY>
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</HTML>
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