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* @Id: clear.1,v 1.48 2024/03/16 15:35:01 tom Exp @

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<TITLE>clear 1 2024-03-16 ncurses 6.5 User commands</TITLE>

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<H1 class="no-header">clear 1 2024-03-16 ncurses 6.5 User commands</H1>

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<PRE>

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<A HREF="clear.1.html">clear(1)</A> User commands <A HREF="clear.1.html">clear(1)</A>

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</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>

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clear - clear the terminal screen

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</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>

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clear [-x] [-T terminal-type]

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clear -V

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</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>

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clear clears your terminal's screen and its scrollback buffer, if any.

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clear retrieves the terminal type from the environment variable TERM,

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then consults the terminfo terminal capability database entry for that

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type to determine how to perform these actions.

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The capabilities to clear the screen and scrollback buffer are named

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"clear" and "E3", respectively. The latter is a user-defined

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capability, applying an extension mechanism introduced in ncurses 5.0

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(1999).

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</PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>

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clear recognizes the following options.

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-T type produces instructions suitable for the terminal type.

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Normally, this option is unnecessary, because the terminal

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type is inferred from the environment variable TERM. If this

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option is specified, clear ignores the environment variables

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LINES and COLUMNS as well.

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-V reports the version of ncurses associated with this program

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and exits with a successful status.

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-x prevents clear from attempting to clear the scrollback buffer.

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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 Specifications Issue 7

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(POSIX.1-2008) nor X/Open Curses Issue 7 documents clear.

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The latter documents tput, 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

run tput as clear.

</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>

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A clear command using the termcap database and library appeared in 2BSD

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(1979). Eighth Edition Unix (1985) later included it.

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The commercial Unix arm of AT&T adapted a different BSD program (tset)

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to make a new command, tput, and replaced the clear program with a

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shell script that called "tput clear".

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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 tput command to make it

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similar to AT&T's tput, he added a clear shell script as well.

exec tput clear

The remainder of the script in each case is a copyright notice.

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In 1995, ncurses's clear began by adapting BSD's original clear command

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to use terminfo. The E3 extension came later.

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o In June 1999, xterm provided an extension to the standard control

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sequence for clearing the screen. Rather than clearing just the

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visible part of the screen using

printf '\033[2J'

one could clear the scrollback buffer as well by using

printf '\033[3J'

instead. "XTerm Control Sequences" documents this feature as

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originating with xterm.

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o A few other terminal emulators adopted it, such as PuTTY in 2006.

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o 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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Documentation of this change, appearing in Linux 3.0, did not

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mention xterm, although that program was cited in the Red Hat bug

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report (#683733) motivating the feature.

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o Subsequently, more terminal developers adopted the feature. The

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next relevant step was to change the ncurses clear program in 2013

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to incorporate this extension.

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o In 2013, the E3 capability was not exercised by "tput clear". That

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oversight was addressed in 2016 by reorganizing tput to share its

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logic with clear and tset.

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</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>

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<A HREF="tput.1.html">tput(1)</A>, xterm(1), <A HREF="terminfo.5.html">terminfo(5)</A>

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ncurses 6.5 2024-03-16 <A HREF="clear.1.html">clear(1)</A>

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</PRE>

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<ul>

<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-OPTIONS">OPTIONS</a></li>

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<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>

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<li><a href="#h2-HISTORY">HISTORY</a></li>

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</ul>

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</div>

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