* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************
- * @Id: clear.1,v 1.14 2016/11/19 21:30:46 tom Exp @
+ * @Id: clear.1,v 1.16 2016/12/31 16:09:34 tom Exp @
* these would be fallbacks for DS/DE,
* but groff changed the meaning of the macros.
-->
<STRONG>clear</STRONG> clears your screen if this is possible, including
its scrollback buffer (if the extended "E3" capability is
defined). <STRONG>clear</STRONG> looks in the environment for the terminal
- type and then in the <STRONG>terminfo</STRONG> database to determine how to
- clear the screen.
+ type given by the environment variable <STRONG>TERM</STRONG>, and then in
+ the <STRONG>terminfo</STRONG> database to determine how to clear the
+ screen.
+
+ <STRONG>clear</STRONG> writes to the standard output. You can redirect the
+ standard output to a file (which prevents <STRONG>clear</STRONG> from actu-
+ ally clearing the screen), and later <STRONG>cat</STRONG> the file to the
+ screen, clearing it at that point.
<STRONG>clear</STRONG> ignores any command-line parameters that may be
- present.
+ present. The analogous "<STRONG>tput</STRONG> clear" has command-line
+ parameters including <STRONG>-T</STRONG> for overriding the <STRONG>TERM</STRONG> environ-
+ ment variable.
</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
AT&T adapted a different BSD program (<STRONG>tset</STRONG>) to make a new
command (<STRONG>tput</STRONG>), and used this to replace the <STRONG>clear</STRONG> command
with a shell script which calls <STRONG>tput</STRONG> <STRONG>clear</STRONG>, e.g.,
- /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
- exit
+
+ /usr/bin/tput ${1:+-T$1} clear 2> /dev/null
+ exit
In 1989, when Keith Bostic revised the BSD <STRONG>tput</STRONG> command to
make it similar to the AT&T <STRONG>tput</STRONG>, he added a shell script
for the <STRONG>clear</STRONG> command:
- exec tput clear
+
+ exec tput clear
The remainder of the script in each case is a copyright
notice.
dard control sequence for clearing the screen. Rather
than clearing just the visible part of the screen
using
- printf '\033[2J'
+
+ printf '\033[2J'
one could clear the <EM>scrollback</EM> using
- printf '\033[<STRONG>3</STRONG>J'
+
+ printf '\033[<STRONG>3</STRONG>J'
This is documented in <EM>XTerm</EM> <EM>Control</EM> <EM>Sequences</EM> as a
feature originating with xterm.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
- This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20161224).
+ This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20170401).