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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | HISTORY | PORTABILITY | SEE ALSO | COLOPHON |
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@CLEAR@(1) General Commands Manual @CLEAR@(1)
@CLEAR@ - clear the terminal screen
@CLEAR@ [-Ttype] [-V] [-x]
@CLEAR@ clears your terminal's screen if this is possible,
including the terminal's 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” capability.
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@.
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), xterm(1).
This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@
(patch @NCURSES_PATCH@).
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
@CLEAR@(1)
Pages that refer to this page: setterm(1), user_caps(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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