clear 1 2023-10-01 ncurses 6.4 User commands

clear(1)                         User commands                        clear(1)


       clear - clear the terminal screen


       clear [-x] [-T type]

       clear -V


       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


       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.


       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

       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.

       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 buffer using

               printf '\033[3J'

           "XTerm  Control  Sequences"  documents  this feature as originating
           with xterm.

       o   A few other terminal emulators adopted it, such as 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.
           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.

       o   Subsequently, more terminal developers adopted  the  feature.   The
           next  relevant step was to change the ncurses clear program in 2013
           to incorporate this extension.

       o   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.


       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), xterm(1), terminfo(5)

ncurses 6.4                       2023-10-01                          clear(1)