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30 * @Id: clear.1,v 1.23 2020/02/02 23:34:34 tom Exp @
31 * these would be fallbacks for DS/DE,
32 * but groff changed the meaning of the macros.
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44 <H1 class="no-header">clear 1</H1>
46 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG> General Commands Manual <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
51 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
52 <STRONG>clear</STRONG> - clear the terminal screen
55 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
56 <STRONG>clear</STRONG> [<STRONG>-T</STRONG><EM>type</EM>] [<STRONG>-V</STRONG>] [<STRONG>-x</STRONG>]
59 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
60 <STRONG>clear</STRONG> clears your screen if this is possible, including its scrollback
61 buffer (if the extended "E3" capability is defined). <STRONG>clear</STRONG> looks in
62 the environment for the terminal type given by the environment variable
63 <STRONG>TERM</STRONG>, and then in the <STRONG>terminfo</STRONG> database to determine how to clear the
66 <STRONG>clear</STRONG> writes to the standard output. You can redirect the standard
67 output to a file (which prevents <STRONG>clear</STRONG> from actually clearing the
68 screen), and later <STRONG>cat</STRONG> the file to the screen, clearing it at that
72 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
73 <STRONG>-T</STRONG> <EM>type</EM>
74 indicates the <EM>type</EM> of terminal. Normally this option is
75 unnecessary, because the default is taken from the environment
76 variable <STRONG>TERM</STRONG>. If <STRONG>-T</STRONG> is specified, then the shell variables <STRONG>LINES</STRONG>
77 and <STRONG>COLUMNS</STRONG> will also be ignored.
79 <STRONG>-V</STRONG> reports the version of ncurses which was used in this program, and
80 exits. The options are as follows:
82 <STRONG>-x</STRONG> do not attempt to clear the terminal's scrollback buffer using the
83 extended "E3" capability.
86 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
87 A <STRONG>clear</STRONG> command appeared in 2.79BSD dated February 24, 1979. Later
88 that was provided in Unix 8th edition (1985).
90 AT&T adapted a different BSD program (<STRONG>tset</STRONG>) to make a new command
91 (<STRONG>tput</STRONG>), and used this to replace the <STRONG>clear</STRONG> command with a shell script
92 which calls <STRONG>tput</STRONG> <STRONG>clear</STRONG>, e.g.,
94 /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
97 In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to make it
98 similar to the AT&T <STRONG>tput</STRONG>, he added a shell script for the <STRONG>clear</STRONG>
103 The remainder of the script in each case is a copyright notice.
105 The ncurses <STRONG>clear</STRONG> command began in 1995 by adapting the original BSD
106 <STRONG>clear</STRONG> command (with terminfo, of course).
108 The <STRONG>E3</STRONG> extension came later:
110 <STRONG>o</STRONG> In June 1999, xterm provided an extension to the standard control
111 sequence for clearing the screen. Rather than clearing just the
112 visible part of the screen using
116 one could clear the <EM>scrollback</EM> using
118 printf '\033[<STRONG>3</STRONG>J'
120 This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a feature
121 originating with xterm.
123 <STRONG>o</STRONG> A few other terminal developers adopted the feature, e.g., PuTTY in
126 <STRONG>o</STRONG> In April 2011, a Red Hat developer submitted a patch to the Linux
127 kernel, modifying its console driver to do the same thing. The
128 Linux change, part of the 3.0 release, did not mention xterm,
129 although it was cited in the Red Hat bug report (#683733) which led
132 <STRONG>o</STRONG> Again, a few other terminal developers adopted the feature. But
133 the next relevant step was a change to the <STRONG>clear</STRONG> program in 2013 to
134 incorporate this extension.
136 <STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> extension was overlooked in <STRONG>tput</STRONG> with the "clear"
137 parameter. That was addressed in 2016 by reorganizing <STRONG>tput</STRONG> to
138 share its logic with <STRONG>clear</STRONG> and <STRONG>tset</STRONG>.
141 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
142 Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
143 (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.
145 The latter documents <STRONG>tput</STRONG>, which could be used to replace this utility
146 either via a shell script or by an alias (such as a symbolic link) to
147 run <STRONG>tput</STRONG> as <STRONG>clear</STRONG>.
150 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
151 <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
153 This describes <STRONG>ncurses</STRONG> version 6.2 (patch 20210403).
157 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
161 <li><a href="#h2-NAME">NAME</a></li>
162 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
163 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
164 <li><a href="#h2-OPTIONS">OPTIONS</a></li>
165 <li><a href="#h2-HISTORY">HISTORY</a></li>
166 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
167 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>