clear

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
            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” 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
       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.

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 6.2 (patch 20200212).



                                                                        clear(1)