clear(1)



clear(1)                    General Commands Manual                   clear(1)

NAME
       clear - clear the terminal screen

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

DESCRIPTION
       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.

OPTIONS
       -T type
            indicates the type of terminal.  Normally this option is  unneces-
            sary,  because  the default is taken from the environment variable
            TERM.

       -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" capability.

HISTORY
       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
         exit

       In 1989, when Keith Bostic revised the BSD tput command to make it sim-
       ilar 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:

       o   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 origi-
           nating with xterm.

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

       o   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.

       o   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.

       o   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.

PORTABILITY
       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.

SEE ALSO
       tput(1), terminfo(5)

       This describes ncurses version 6.0 (patch 20170902).

                                                                      clear(1)

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