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28 ****************************************************************************
29 * @Id: clear.1,v 1.16 2016/12/31 16:09:34 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>
58 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
59 <STRONG>clear</STRONG> clears your screen if this is possible, including
60 its scrollback buffer (if the extended "E3" capability is
61 defined). <STRONG>clear</STRONG> looks in the environment for the terminal
62 type given by the environment variable <STRONG>TERM</STRONG>, and then in
63 the <STRONG>terminfo</STRONG> database to determine how to clear the
66 <STRONG>clear</STRONG> writes to the standard output. You can redirect the
67 standard output to a file (which prevents <STRONG>clear</STRONG> from actu-
68 ally clearing the screen), and later <STRONG>cat</STRONG> the file to the
69 screen, clearing it at that point.
71 <STRONG>clear</STRONG> ignores any command-line parameters that may be
72 present. The analogous "<STRONG>tput</STRONG> clear" has command-line
73 parameters including <STRONG>-T</STRONG> for overriding the <STRONG>TERM</STRONG> environ-
77 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
78 A <STRONG>clear</STRONG> command appeared in 2.79BSD dated February 24,
79 1979. Later that was provided in Unix 8th edition (1985).
81 AT&T adapted a different BSD program (<STRONG>tset</STRONG>) to make a new
82 command (<STRONG>tput</STRONG>), and used this to replace the <STRONG>clear</STRONG> command
83 with a shell script which calls <STRONG>tput</STRONG> <STRONG>clear</STRONG>, e.g.,
85 /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
88 In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to
89 make it similar to the AT&T <STRONG>tput</STRONG>, he added a shell script
90 for the <STRONG>clear</STRONG> command:
94 The remainder of the script in each case is a copyright
97 The ncurses <STRONG>clear</STRONG> command began in 1995 by adapting the
98 original BSD <STRONG>clear</STRONG> command (with terminfo, of course).
100 The <STRONG>E3</STRONG> extension came later:
102 <STRONG>o</STRONG> In June 1999, xterm provided an extension to the stan-
103 dard control sequence for clearing the screen. Rather
104 than clearing just the visible part of the screen
109 one could clear the <EM>scrollback</EM> using
111 printf '\033[<STRONG>3</STRONG>J'
113 This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a
114 feature originating with xterm.
116 <STRONG>o</STRONG> A few other terminal developers adopted the feature,
119 <STRONG>o</STRONG> In April 2011, a Red Hat developer submitted a patch
120 to the Linux kernel, modifying its console driver to
121 do the same thing. The Linux change, part of the 3.0
122 release, did not mention xterm, although it was cited
123 in the Red Hat bug report (#683733) which led to the
126 <STRONG>o</STRONG> Again, a few other terminal developers adopted the
127 feature. But the next relevant step was a change to
128 the <STRONG>clear</STRONG> program in 2013 to incorporate this exten-
131 <STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> extension was overlooked in <STRONG>tput</STRONG> with
132 the "clear" parameter. That was addressed in 2016 by
133 reorganizing <STRONG>tput</STRONG> to share its logic with <STRONG>clear</STRONG> and
134 <STRONG>tset</STRONG>.
137 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
138 Neither IEEE Std 1003.1/The Open Group Base Specifica-
139 tions Issue 7 (POSIX.1-2008) nor X/Open Curses Issue 7
140 documents tset or reset.
142 The latter documents <STRONG>tput</STRONG>, which could be used to replace
143 this utility either via a shell script or by an alias
144 (such as a symbolic link) to 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 20170304).
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-HISTORY">HISTORY</a></li>
162 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
163 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>