clear(1)			 User commands			      clear(1)

NAME
       clear - clear the terminal screen

SYNOPSIS
       clear [-x] [-T terminal-type]

       clear -V

DESCRIPTION
       clear clears your terminal's screen and its scrollback buffer, if any.
       clear retrieves the terminal type from the environment variable TERM,
       then consults the terminfo terminal capability database entry for that
       type to determine how to perform these actions.

       The capabilities to clear the screen and scrollback buffer are named
       “clear” and “E3”, respectively.	The latter is a user-defined
       capability, applying an extension mechanism introduced in ncurses 5.0
       (1999).

OPTIONS
       clear recognizes the following options.

       -T type	produces instructions suitable for the terminal type.
		Normally, this option is unnecessary, because the terminal
		type is inferred from the environment variable TERM.  If this
		option is specified, clear ignores the environment variables
		LINES and COLUMNS as well.

       -V	reports the version of ncurses associated with this program
		and exits with a successful status.

       -x	prevents clear from attempting to clear the scrollback buffer.

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

       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.

HISTORY
       A clear command using the termcap database and library appeared in 2BSD
       (1979).	Eighth Edition Unix (1985) later included it.

       The commercial Unix arm of AT&T adapted a different BSD program (tset)
       to make a new command, tput, and replaced the clear program with a
       shell script that called “tput clear”.

	   /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 AT&T's tput, he added a clear shell script as well.

	   exec tput clear

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

       In 1995, ncurses's clear began by adapting BSD's original clear command
       to use terminfo.	 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 buffer as well by using

	       printf '\033[3J'

	   instead.  “XTerm Control Sequences” documents this feature as
	   originating with xterm.

       •   A few other terminal emulators adopted it, such as 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.
	   Documentation of this change, appearing in Linux 3.0, did not
	   mention xterm, although that program was cited in the Red Hat bug
	   report (#683733) motivating the feature.

       •   Subsequently, more terminal developers adopted the feature.	The
	   next relevant step was to change the ncurses clear program in 2013
	   to incorporate this extension.

       •   In 2013, the E3 capability was not exercised by “tput clear”.  That
	   oversight was addressed in 2016 by reorganizing tput to share its
	   logic with clear and tset.

SEE ALSO
       tput(1), xterm(1), terminfo(5)

ncurses 6.5			  2024-03-16			      clear(1)