noble (1) clear.1.gz

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)