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30 * @Id: clear.1,v 1.27 2022/02/12 20:07:29 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 terminal's screen if this is possible, including the
61 terminal's scrollback buffer (if the extended "E3" capability is
62 defined). <STRONG>clear</STRONG> looks in the environment for the terminal type given
63 by the environment variable <STRONG>TERM</STRONG>, and then in the <STRONG>terminfo</STRONG> database to
64 determine how to clear the screen.
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, <STRONG>xterm</STRONG> 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 <STRONG>xterm</STRONG>.
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 <STRONG>xterm</STRONG>,
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>, <STRONG>xterm(1)</STRONG>.
153 This describes <STRONG>ncurses</STRONG> version 6.3 (patch 20220212).
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>