man > clear

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  capa‐
       bility 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”, re‐
       spectively.  The latter is a user-defined capability, applying an extension mechanism  intro‐
       duced in ncurses 5.0 (1999).

OPTIONS
       clear recognizes the following options.

       -T type  produces  instructions suitable for the terminal type.  Normally, this option is un‐
                necessary, 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 suc‐
                cessful 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  Edi‐
       tion 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  ad‐
           dressed in 2016 by reorganizing tput to share its logic with clear and tset.

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

ncurses 6.4                                  2023-12-16                                     clear(1)