Provided by: ncurses-bin_6.2-0ubuntu2.1_amd64 bug


       clear - clear the terminal screen


       clear [-Ttype] [-V] [-x]


       clear  clears  your  screen  if  this is possible, including its scrollback buffer (if the
       extended “E3” capability is defined).  clear looks in the  environment  for  the  terminal
       type  given  by  the  environment  variable  TERM,  and  then  in the terminfo database to
       determine how to clear the screen.

       clear writes to the standard output.  You can redirect  the  standard  output  to  a  file
       (which  prevents  clear  from actually clearing the screen), and later cat the file to the
       screen, clearing it at that point.


       -T type
            indicates the type of terminal.  Normally this option  is  unnecessary,  because  the
            default  is  taken  from the environment variable TERM.  If -T is specified, then the
            shell variables LINES and COLUMNS will also be ignored.

       -V   reports the version of ncurses which was  used  in  this  program,  and  exits.   The
            options are as follows:

       -x   do  not  attempt  to  clear  the terminal's scrollback buffer using the extended “E3”


       A clear command appeared in 2.79BSD dated February 24, 1979.  Later that was  provided  in
       Unix 8th edition (1985).

       AT&T adapted a different BSD program (tset) to make a new command (tput), and used this to
       replace the clear command with a shell script which calls tput clear, e.g.,

           /usr/bin/tput ${1:+-T$1} clear 2> /dev/null

       In 1989, when Keith Bostic revised the BSD tput command to make it  similar  to  the  AT&T
       tput, he added a shell script for the clear command:

           exec tput clear

       The remainder of the script in each case is a copyright notice.

       The  ncurses  clear command began in 1995 by adapting the original BSD clear command (with
       terminfo, of course).

       The E3 extension came later:

       •   In June 1999, xterm provided  an  extension  to  the  standard  control  sequence  for
           clearing the screen.  Rather than clearing just the visible part of the screen using

               printf '\033[2J'

           one could clear the scrollback using

               printf '\033[3J'

           This is documented in XTerm Control Sequences as a feature originating with xterm.

       •   A few other terminal developers adopted the feature, e.g., PuTTY in 2006.

       •   In  April  2011,  a Red Hat developer submitted a patch to the Linux kernel, modifying
           its console driver to do the same thing.  The Linux change, part of the  3.0  release,
           did not mention xterm, although it was cited in the Red Hat bug report (#683733) which
           led to the change.

       •   Again, a few other terminal developers adopted the feature.   But  the  next  relevant
           step was a change to the clear program in 2013 to incorporate this extension.

       •   In 2013, the E3 extension was overlooked in tput with the “clear” parameter.  That was
           addressed in 2016 by reorganizing tput to share its logic with clear and tset.


       Neither IEEE Std 1003.1/The Open  Group  Base  Specifications  Issue  7 (POSIX.1-2008) nor
       X/Open Curses Issue 7 documents tset or reset.

       The  latter documents tput, which could be used to replace this utility either via a shell
       script or by an alias (such as a symbolic link) to run tput as clear.


       tput(1), terminfo(5)

       This describes ncurses version 6.2 (patch 20200212).