- clear clears your screen if this is possible. It looks in
- the environment for the terminal type and then in the ter-
- minfo database to figure out how to clear the screen.
+
+ 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 ignores any command-line parameters that may be
- present.
+ 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.
-
+ -Ttype
+ 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.
+
+
+
+ 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 tputclear, 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 XTermControlSequences 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.
+
+
+
+ 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.
+
+
+