1clear(1)                    General Commands Manual                   clear(1)
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NAME

6       clear - clear the terminal screen
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SYNOPSIS

9       clear [-Ttype] [-V] [-x]
10

DESCRIPTION

12       clear  clears your screen if this is possible, including its scrollback
13       buffer (if the extended “E3” capability is defined).   clear  looks  in
14       the environment for the terminal type given by the environment variable
15       TERM, and then in the terminfo database to determine how to  clear  the
16       screen.
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18       clear  writes  to  the  standard output.  You can redirect the standard
19       output to a file (which  prevents  clear  from  actually  clearing  the
20       screen),  and  later  cat  the  file to the screen, clearing it at that
21       point.
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OPTIONS

24       -T type
25            indicates the type of terminal.  Normally this option is  unneces‐
26            sary,  because  the default is taken from the environment variable
27            TERM.  If -T is specified, then the shell variables LINES and COL‐
28            UMNS will also be ignored.
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30       -V   reports the version of ncurses which was used in this program, and
31            exits.  The options are as follows:
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33       -x   do not attempt to clear the terminal's scrollback buffer using the
34            extended “E3” capability.
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HISTORY

37       A  clear  command  appeared  in 2.79BSD dated February 24, 1979.  Later
38       that was provided in Unix 8th edition (1985).
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40       AT&T adapted a different BSD program  (tset)  to  make  a  new  command
41       (tput),  and used this to replace the clear command with a shell script
42       which calls tput clear, e.g.,
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44           /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
45           exit
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47       In 1989, when Keith Bostic revised the BSD tput command to make it sim‐
48       ilar to the AT&T tput, he added a shell script for the clear command:
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50           exec tput clear
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52       The remainder of the script in each case is a copyright notice.
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54       The  ncurses  clear  command began in 1995 by adapting the original BSD
55       clear command (with terminfo, of course).
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57       The E3 extension came later:
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59       ·   In June 1999, xterm provided an extension to the  standard  control
60           sequence  for  clearing  the screen.  Rather than clearing just the
61           visible part of the screen using
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63               printf '\033[2J'
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65           one could clear the scrollback using
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67               printf '\033[3J'
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69           This is documented in XTerm Control Sequences as a  feature  origi‐
70           nating with xterm.
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72       ·   A few other terminal developers adopted the feature, e.g., PuTTY in
73           2006.
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75       ·   In April 2011, a Red Hat developer submitted a patch to  the  Linux
76           kernel,  modifying  its  console  driver to do the same thing.  The
77           Linux change, part of the  3.0  release,  did  not  mention  xterm,
78           although it was cited in the Red Hat bug report (#683733) which led
79           to the change.
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81       ·   Again, a few other terminal developers adopted  the  feature.   But
82           the next relevant step was a change to the clear program in 2013 to
83           incorporate this extension.
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85       ·   In 2013, the E3 extension was overlooked in tput with  the  “clear”
86           parameter.   That  was  addressed  in  2016 by reorganizing tput to
87           share its logic with clear and tset.
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PORTABILITY

90       Neither IEEE Std 1003.1/The Open  Group  Base  Specifications  Issue  7
91       (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.
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93       The  latter documents tput, which could be used to replace this utility
94       either via a shell script or by an alias (such as a symbolic  link)  to
95       run tput as clear.
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SEE ALSO

98       tput(1), terminfo(5)
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100       This describes ncurses version 6.1 (patch 20180923).
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