clear(1) clear(1)
clear - clear the terminal screen
clear
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 actu-
ally clearing the screen), and later cat the file to the
screen, clearing it at that point.
clear ignores any command-line parameters that may be
present. The analogous "tput clear" has command-line
parameters including -T for overriding the TERM environ-
ment variable.
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:
o In June 1999, xterm provided an extension to the stan-
dard 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.
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 exten-
sion.
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.
Neither IEEE Std 1003.1/The Open Group Base Specifica-
tions 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 6.0 (patch 20170318).
clear(1)