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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 unneces-
75 sary, because the default is taken from the environment variable
76 <STRONG>TERM</STRONG>. If <STRONG>-T</STRONG> is specified, then the shell variables <STRONG>LINES</STRONG> and <STRONG>COL-</STRONG>
77 <STRONG>UMNS</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 sim-
98 ilar to the AT&T <STRONG>tput</STRONG>, he added a shell script for the <STRONG>clear</STRONG> command:
102 The remainder of the script in each case is a copyright notice.
104 The ncurses <STRONG>clear</STRONG> command began in 1995 by adapting the original BSD
105 <STRONG>clear</STRONG> command (with terminfo, of course).
107 The <STRONG>E3</STRONG> extension came later:
109 <STRONG>o</STRONG> In June 1999, xterm provided an extension to the standard control
110 sequence for clearing the screen. Rather than clearing just the
111 visible part of the screen using
115 one could clear the <EM>scrollback</EM> using
117 printf '\033[<STRONG>3</STRONG>J'
119 This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a feature origi-
122 <STRONG>o</STRONG> A few other terminal developers adopted the feature, e.g., PuTTY in
125 <STRONG>o</STRONG> In April 2011, a Red Hat developer submitted a patch to the Linux
126 kernel, modifying its console driver to do the same thing. The
127 Linux change, part of the 3.0 release, did not mention xterm,
128 although it was cited in the Red Hat bug report (#683733) which led
131 <STRONG>o</STRONG> Again, a few other terminal developers adopted the feature. But
132 the next relevant step was a change to the <STRONG>clear</STRONG> program in 2013 to
133 incorporate this extension.
135 <STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> extension was overlooked in <STRONG>tput</STRONG> with the "clear"
136 parameter. That was addressed in 2016 by reorganizing <STRONG>tput</STRONG> to
137 share its logic with <STRONG>clear</STRONG> and <STRONG>tset</STRONG>.
140 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
141 Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
142 (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.
144 The latter documents <STRONG>tput</STRONG>, which could be used to replace this utility
145 either via a shell script or by an alias (such as a symbolic link) to
146 run <STRONG>tput</STRONG> as <STRONG>clear</STRONG>.
149 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
150 <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
152 This describes <STRONG>ncurses</STRONG> version 6.2 (patch 20200212).
156 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
160 <li><a href="#h2-NAME">NAME</a></li>
161 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
162 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
163 <li><a href="#h2-OPTIONS">OPTIONS</a></li>
164 <li><a href="#h2-HISTORY">HISTORY</a></li>
165 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
166 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>