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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/\
  33   *   tput/clear.sh
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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>
  46 <PRE>
  47 <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>                         User commands                        <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
  48
  49
  50
  51
  52 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
  53        <STRONG>clear</STRONG> - clear the terminal screen
  54
  55
  56 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
  57        <STRONG>clear</STRONG> [<STRONG>-x</STRONG>] [<STRONG>-T</STRONG> <EM>type</EM>]
  58
  59        <STRONG>clear</STRONG> <STRONG>-V</STRONG>
  60
  61
  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.
  67
  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
  71        (1999).
  72
  73
  74 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
  75        <STRONG>clear</STRONG> recognizes the following options.
  76
  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.
  82
  83        <STRONG>-V</STRONG>       reports  the  version  of <EM>ncurses</EM> associated with this program
  84                 and exits with a successful status.
  85
  86        <STRONG>-x</STRONG>       prevents <STRONG>clear</STRONG> from attempting to clear the scrollback buffer.
  87
  88
  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.
  92
  93        The  commercial Unix arm of AT&amp;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>".
  96
  97            /usr/bin/tput ${1:+-T$1} clear 2&gt; /dev/null
  98            exit
  99
 100        In  1989,  when  Keith  Bostic  revised the BSD <STRONG>tput</STRONG> command to make it
 101        similar to AT&amp;T's <STRONG>tput</STRONG>, he added a <STRONG>clear</STRONG> shell script as well.
 102
 103            exec tput clear
 104
 105        The remainder of the script in each case is a copyright notice.
 106
 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.
 109
 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
 113
 114                printf '\033[2J'
 115
 116            one could clear the scrollback buffer using
 117
 118                printf '\033[<STRONG>3</STRONG>J'
 119
 120            "XTerm  Control  Sequences"  documents  this feature as originating
 121            with <EM>xterm</EM>.
 122
 123        <STRONG>o</STRONG>   A few other terminal emulators adopted it, such as PuTTY in 2006.
 124
 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.
 130
 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.
 134
 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>.
 138
 139
 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>.
 143
 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>.
 147
 148
 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>
 151
 152
 153
 154 ncurses 6.4                       2023-10-01                          <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>
 155 </PRE>
 156 <div class="nav">
 157 <ul>
 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>
 165 </ul>
 166 </div>
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