clear(3NCURSES) Library calls clear(3NCURSES)
NAME
erase, werase, clear, wclear, clrtobot, wclrtobot, clrtoeol, wclrtoeol -
clear all or part of a curses window
SYNOPSIS
#include <curses.h>
int erase(void);
int werase(WINDOW *win);
int clear(void);
int wclear(WINDOW *win);
int clrtobot(void);
int wclrtobot(WINDOW *win);
int clrtoeol(void);
int wclrtoeol(WINDOW *win);
DESCRIPTION
erase, werase
The erase and werase routines copy blanks to every position in the win-
dow, clearing the screen.
Blanks created by erasure have the current background rendition (as set
by wbkgdset(3NCURSES)) merged into them.
clear, wclear
The clear and wclear routines are like erase and werase, but they also
call clearok(3NCURSES), so that the screen is cleared completely on the
next call to wrefresh for that window and repainted from scratch.
clrtobot, wclrtobot
The clrtobot and wclrtobot routines erase from the cursor to the end of
screen. That is, they erase all lines below the cursor in the window.
Also, the current line to the right of the cursor, inclusive, is erased.
clrtoeol, wclrtoeol
The clrtoeol and wclrtoeol routines erase the current line to the right
of the cursor, inclusive, to the end of the current line.
RETURN VALUE
All routines return the integer OK on success and ERR on failure.
In this implementation,
• functions using a window pointer parameter return ERR if it is null
• wclrtoeol returns an error if the cursor position is about to wrap.
NOTES
erase, werase, clear, wclear, clrtobot, and clrtoeol may be implemented
as macros.
PORTABILITY
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
SVr4 documentation says that these functions return OK “or a non-nega-
tive integer if immedok() is set”, referring to the return value from
wrefresh, which in SVr4 returns a count of characters written to the
window if its immedok property is set; in ncurses, it does not.
Some historic curses implementations had, as an undocumented feature,
the ability to do the equivalent of clearok(..., 1) by saying touch-
win(stdscr) or clear(stdscr). This will not work under ncurses.
This implementation, and others such as Solaris, sets the current posi-
tion to 0,0 after erasing via werase and wclear. That fact is not docu-
mented in other implementations, and may not be true of implementations
which were not derived from SVr4 source.
Not obvious from the description, most implementations clear the screen
after wclear even for a subwindow or derived window. If you do not want
to clear the screen during the next wrefresh, use werase instead.
SEE ALSO
ncurses(3NCURSES), outopts(3NCURSES), refresh(3NCURSES),
curses_variables(3NCURSES)
ncurses 6.5 2025-01-18 clear(3NCURSES)
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