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30 * @Id: clear.1,v 1.40 2023/10/01 22:12:38 tom Exp @
31 * https://minnie.tuhs.org/cgi-bin/utree.pl?file=2BSD/src/clear.c
32 * https://minnie.tuhs.org/cgi-bin/utree.pl?file=Net2/usr/src/usr.bin/\
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40 <TITLE>clear 1 2023-10-01 ncurses 6.4 User commands</TITLE>
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45 <H1 class="no-header">clear 1 2023-10-01 ncurses 6.4 User commands</H1>
47 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG> User commands <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
52 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
53 <STRONG>clear</STRONG> - clear the terminal screen
56 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
57 <STRONG>clear</STRONG> [<STRONG>-x</STRONG>] [<STRONG>-T</STRONG> <EM>type</EM>]
59 <STRONG>clear</STRONG> <STRONG>-V</STRONG>
62 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
63 <STRONG>clear</STRONG> clears your terminal's screen and its scrollback buffer, if any.
64 <STRONG>clear</STRONG> retrieves the terminal type from the environment variable <STRONG>TERM</STRONG>,
65 then consults the <EM>terminfo</EM> terminal capability database entry for that
66 type to determine how to perform these actions.
68 The capabilities to clear the screen and scrollback buffer are named
69 "clear" and "E3", respectively. The latter is a <EM>user-defined</EM>
70 <EM>capability</EM>, applying an extension mechanism introduced in <EM>ncurses</EM> 5.0
74 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
75 <STRONG>clear</STRONG> recognizes the following options.
77 <STRONG>-T</STRONG> <EM>type</EM> produces instructions suitable for the terminal <EM>type</EM>.
78 Normally, this option is unnecessary, because the terminal
79 type is inferred from the environment variable <STRONG>TERM</STRONG>. If this
80 option is specified, <STRONG>clear</STRONG> ignores the environment variables
81 <STRONG>LINES</STRONG> and <STRONG>COLUMNS</STRONG> as well.
83 <STRONG>-V</STRONG> reports the version of <EM>ncurses</EM> associated with this program
84 and exits with a successful status.
86 <STRONG>-x</STRONG> prevents <STRONG>clear</STRONG> from attempting to clear the scrollback buffer.
89 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
90 A <STRONG>clear</STRONG> command using the <EM>termcap</EM> database and library appeared in 2BSD
91 (1979). Eighth Edition Unix (1985) later included it.
93 The commercial Unix arm of AT&T adapted a different BSD program (<STRONG>tset</STRONG>)
94 to make a new command, <STRONG>tput</STRONG>, and replaced the <STRONG>clear</STRONG> program with a
95 shell script that called "<STRONG>tput</STRONG> <STRONG>clear</STRONG>".
97 /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
100 In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to make it
101 similar to AT&T's <STRONG>tput</STRONG>, he added a <STRONG>clear</STRONG> shell script as well.
105 The remainder of the script in each case is a copyright notice.
107 In 1995, <EM>ncurses</EM>'s <STRONG>clear</STRONG> began by adapting BSD's original <STRONG>clear</STRONG> command
108 to use <EM>terminfo</EM>. The <STRONG>E3</STRONG> extension came later.
110 <STRONG>o</STRONG> In June 1999, <EM>xterm</EM> 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 scrollback buffer using
118 printf '\033[<STRONG>3</STRONG>J'
120 "XTerm Control Sequences" documents this feature as originating
123 <STRONG>o</STRONG> A few other terminal emulators adopted it, such as PuTTY in 2006.
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.
127 Documentation of this change, appearing in Linux 3.0, did not
128 mention <EM>xterm</EM>, although that program was cited in the Red Hat bug
129 report (#683733) motivating the feature.
131 <STRONG>o</STRONG> Subsequently, more terminal developers adopted the feature. The
132 next relevant step was to change the <EM>ncurses</EM> <STRONG>clear</STRONG> program in 2013
133 to incorporate this extension.
135 <STRONG>o</STRONG> In 2013, the <STRONG>E3</STRONG> capability was not exercised by "<STRONG>tput</STRONG> <STRONG>clear</STRONG>". That
136 oversight was addressed in 2016 by reorganizing <STRONG>tput</STRONG> to share its
137 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 <STRONG>tset</STRONG> or <STRONG>reset</STRONG>.
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>xterm(1)</STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
154 ncurses 6.4 2023-10-01 <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>