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29 * @Id: clear.1,v 1.17 2017/08/19 14:12:50 tom Exp @
30 * these would be fallbacks for DS/DE,
31 * but groff changed the meaning of the macros.
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43 <H1 class="no-header">clear 1</H1>
45 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG> <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
50 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
51 <STRONG>clear</STRONG> - clear the terminal screen
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>clear</STRONG> [<STRONG>-T</STRONG><EM>type</EM>] [<STRONG>-V</STRONG>] [<STRONG>-x</STRONG>]
58 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
59 <STRONG>clear</STRONG> clears your screen if this is possible, including its scrollback
60 buffer (if the extended "E3" capability is defined). <STRONG>clear</STRONG> looks in
61 the environment for the terminal type given by the environment variable
62 <STRONG>TERM</STRONG>, and then in the <STRONG>terminfo</STRONG> database to determine how to clear the
65 <STRONG>clear</STRONG> writes to the standard output. You can redirect the standard
66 output to a file (which prevents <STRONG>clear</STRONG> from actually clearing the
67 screen), and later <STRONG>cat</STRONG> the file to the screen, clearing it at that
71 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
72 <STRONG>-T</STRONG> <EM>type</EM>
73 indicates the <EM>type</EM> of terminal. Normally this option is unneces-
74 sary, because the default is taken from the environment variable
75 <STRONG>TERM</STRONG>.
77 <STRONG>-V</STRONG> reports the version of ncurses which was used in this program, and
78 exits. The options are as follows:
80 <STRONG>-x</STRONG> do not attempt to clear the terminal's scrollback buffer using the
81 extended "E3" capability.
84 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
85 A <STRONG>clear</STRONG> command appeared in 2.79BSD dated February 24, 1979. Later
86 that was provided in Unix 8th edition (1985).
88 AT&T adapted a different BSD program (<STRONG>tset</STRONG>) to make a new command
89 (<STRONG>tput</STRONG>), and used this to replace the <STRONG>clear</STRONG> command with a shell script
90 which calls <STRONG>tput</STRONG> <STRONG>clear</STRONG>, e.g.,
92 /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
95 In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to make it sim-
96 ilar to the AT&T <STRONG>tput</STRONG>, he added a shell script for the <STRONG>clear</STRONG> command:
100 The remainder of the script in each case is a copyright notice.
102 The ncurses <STRONG>clear</STRONG> command began in 1995 by adapting the original BSD
103 <STRONG>clear</STRONG> command (with terminfo, of course).
105 The <STRONG>E3</STRONG> extension came later:
107 <STRONG>o</STRONG> In June 1999, xterm provided an extension to the standard control
108 sequence for clearing the screen. Rather than clearing just the
109 visible part of the screen using
113 one could clear the <EM>scrollback</EM> using
115 printf '\033[<STRONG>3</STRONG>J'
117 This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a feature origi-
120 <STRONG>o</STRONG> A few other terminal developers adopted the feature, e.g., PuTTY in
123 <STRONG>o</STRONG> In April 2011, a Red Hat developer submitted a patch to the Linux
124 kernel, modifying its console driver to do the same thing. The
125 Linux change, part of the 3.0 release, did not mention xterm,
126 although it was cited in the Red Hat bug report (#683733) which led
129 <STRONG>o</STRONG> Again, a few other terminal developers adopted the feature. But
130 the next relevant step was a change to the <STRONG>clear</STRONG> program in 2013 to
131 incorporate this extension.
133 <STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> extension was overlooked in <STRONG>tput</STRONG> with the "clear"
134 parameter. That was addressed in 2016 by reorganizing <STRONG>tput</STRONG> to
135 share its logic with <STRONG>clear</STRONG> and <STRONG>tset</STRONG>.
138 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
139 Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
140 (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.
142 The latter documents <STRONG>tput</STRONG>, which could be used to replace this utility
143 either via a shell script or by an alias (such as a symbolic link) to
144 run <STRONG>tput</STRONG> as <STRONG>clear</STRONG>.
147 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
148 <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
150 This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20170819).
154 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
158 <li><a href="#h2-NAME">NAME</a></li>
159 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
160 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
161 <li><a href="#h2-OPTIONS">OPTIONS</a></li>
162 <li><a href="#h2-HISTORY">HISTORY</a></li>
163 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
164 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>