Clearing the screen by printing a character?

Question

I\'m using chez-scheme and I can\'t find a way to clear the screen completely. (If someone knows a better way than printing I\'d be interested in that too but it\'s not my q

Answer 1

You can print \033c which resets the terminal:

petite -q <<< '(display "\033c")'

\033 is escape and c is literal c.

I can't give you any information about how widely this is supported.

Answer 2

If you want to clear the screen, the "ANSI" sequence in a printf

\033[2J

clears the entire screen, e.g.,

printf '\033[2J'

The command-line clear program uses this, along with moving the cursor to the "home" position, again an "ANSI" sequence:

\033[H

The program gets the information from the terminal database. For example, for TERM=vt100, it might see this (using \E as \033):

clear=\E[H\E[J$<50>

(the $<50> indicates padding needed for real VT100s). You might notice that the 2 is absent from this string. That is because the cursor is first moved to the home (upper left) position, and the 2 (entire screen) is not necessary. Eliminating that from the string made VT100s a little faster.

On the other hand, if you just want to reset the terminal, you can use the VT100-style RIS:

\033c

but that has side-effects, besides not being in ECMA-48. These bug reports were for side-effects of \033c:

• Debian Bug report logs - #60377 "reset" broken for dumb terminals
• Debian Bug report logs - #239205 "reset changes a unicode console to non-unicode"

Further reading:

• Why doesn't the screen clear when I type control/L?
• XTerm Control Sequences

CSI Ps J  Erase in Display (ED).
            Ps = 0  -> Erase Below (default).
            Ps = 1  -> Erase Above.
            Ps = 2  -> Erase All.
            Ps = 3  -> Erase Saved Lines (xterm).

• ECMA-48: Control Functions for Coded Character Sets