1clear(1) General Commands Manual clear(1)
2
6 clear - clear the terminal screen
7
9 clear [-Ttype] [-V] [-x]
10
12 clear clears your terminal's screen if this is possible, including the
13 terminal's scrollback buffer (if the extended “E3” capability is de‐
14 fined). clear looks in the environment for the terminal type given by
15 the environment variable TERM, and then in the terminfo database to de‐
16 termine how to clear the screen.
17 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.
22
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.
29 -V reports the version of ncurses which was used in this program, and
31 exits. The options are as follows:
32 -x do not attempt to clear the terminal's scrollback buffer using the
34 extended “E3” capability.
35
37 A clear command appeared in 2.79BSD dated February 24, 1979. Later
38 that was provided in Unix 8th edition (1985).
39 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.,
43 /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
45 exit
46 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:
49 exec tput clear
51 The remainder of the script in each case is a copyright notice.
53 The ncurses clear command began in 1995 by adapting the original BSD
55 clear command (with terminfo, of course).
56 The E3 extension came later:
58 • 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
62 printf '\033[2J'
64 one could clear the scrollback using
66 printf '\033[3J'
68 This is documented in XTerm Control Sequences as a feature origi‐
70 nating with xterm.
71 • A few other terminal developers adopted the feature, e.g., PuTTY in
73 2006.
74 • 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, al‐
78 though it was cited in the Red Hat bug report (#683733) which led
79 to the change.
80 • 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.
84 • 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.
88
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.
92 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.
96
98 tput(1), terminfo(5), xterm(1).
99 This describes ncurses version 6.3 (patch 20220501).
101 clear(1)