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  30   * @Id: clear.1,v 1.43 2023/11/25 14:32:36 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 2023-11-25 ncurses 6.4 User commands</TITLE>
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  45 <H1 class="no-header">clear 1 2023-11-25 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>terminal-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-PORTABILITY">PORTABILITY</a></H2><PRE>
  90        Neither IEEE Std 1003.1/The Open  Group  Base  Specifications  Issue  7
  91        (POSIX.1-2008) nor X/Open Curses Issue 7 documents <STRONG>tset</STRONG> or <STRONG>reset</STRONG>.
  92
  93        The  latter documents <STRONG>tput</STRONG>, which could be used to replace this utility
  94        either via a shell script or by an alias (such as a symbolic  link)  to
  95        run <STRONG>tput</STRONG> as <STRONG>clear</STRONG>.
  96
  97
  98 </PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
  99        A <STRONG>clear</STRONG> command using the <EM>termcap</EM> database and library appeared in 2BSD
 100        (1979).  Eighth Edition Unix (1985) later included it.
 101
 102        The commercial Unix arm of AT&amp;T adapted a different BSD program  (<STRONG>tset</STRONG>)
 103        to  make  a  new  command,  <STRONG>tput</STRONG>, and replaced the <STRONG>clear</STRONG> program with a
 104        shell script that called "<STRONG>tput</STRONG> <STRONG>clear</STRONG>".
 105
 106            /usr/bin/tput ${1:+-T$1} clear 2&gt; /dev/null
 107            exit
 108
 109        In 1989, when Keith Bostic revised the BSD  <STRONG>tput</STRONG>  command  to  make  it
 110        similar to AT&amp;T's <STRONG>tput</STRONG>, he added a <STRONG>clear</STRONG> shell script as well.
 111
 112            exec tput clear
 113
 114        The remainder of the script in each case is a copyright notice.
 115
 116        In 1995, <EM>ncurses</EM>'s <STRONG>clear</STRONG> began by adapting BSD's original <STRONG>clear</STRONG> command
 117        to use <EM>terminfo</EM>.  The <STRONG>E3</STRONG> extension came later.
 118
 119        <STRONG>o</STRONG>   In June 1999, <EM>xterm</EM> provided an extension to the  standard  control
 120            sequence  for  clearing  the screen.  Rather than clearing just the
 121            visible part of the screen using
 122
 123                printf '\033[2J'
 124
 125            one could clear the scrollback buffer using
 126
 127                printf '\033[<STRONG>3</STRONG>J'
 128
 129            instead.  "XTerm  Control  Sequences"  documents  this  feature  as
 130            originating with <EM>xterm</EM>.
 131
 132        <STRONG>o</STRONG>   A few other terminal emulators adopted it, such as PuTTY in 2006.
 133
 134        <STRONG>o</STRONG>   In  April  2011, a Red Hat developer submitted a patch to the Linux
 135            kernel,  modifying  its  console  driver  to  do  the  same  thing.
 136            Documentation  of  this  change,  appearing  in  Linux 3.0, did not
 137            mention <EM>xterm</EM>, although that program was cited in the Red  Hat  bug
 138            report (#683733) motivating the feature.
 139
 140        <STRONG>o</STRONG>   Subsequently,  more  terminal  developers adopted the feature.  The
 141            next relevant step was to change the <EM>ncurses</EM> <STRONG>clear</STRONG> program in  2013
 142            to incorporate this extension.
 143
 144        <STRONG>o</STRONG>   In 2013, the <STRONG>E3</STRONG> capability was not exercised by "<STRONG>tput</STRONG> <STRONG>clear</STRONG>".  That
 145            oversight was addressed in 2016 by reorganizing <STRONG>tput</STRONG> to  share  its
 146            logic with <STRONG>clear</STRONG> and <STRONG>tset</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                       2023-11-25                          <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-PORTABILITY">PORTABILITY</a></li>
 163 <li><a href="#h2-HISTORY">HISTORY</a></li>
 164 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
 165 </ul>
 166 </div>
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