Provided by: ncurses-doc_6.1-1ubuntu1_all bug


       erase, werase, clear, wclear, clrtobot, wclrtobot, clrtoeol, wclrtoeol - clear all or part
       of a curses window


       # 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);


       The erase and werase routines copy blanks to every position in the  window,  clearing  the

       The  clear  and  wclear routines are like erase and werase, but they also call clearok, so
       that the screen is cleared completely on the next call to wrefresh  for  that  window  and
       repainted from scratch.

       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.

       The  clrtoeol  and  wclrtoeol  routines erase the current line to the right of the cursor,
       inclusive, to the end of the current line.

       Blanks created by erasure have the current  background  rendition  (as  set  by  wbkgdset)
       merged into them.


       All  routines return the integer OK on success and ERR on failure.  The SVr4.0 manual says
       "or a non-negative integer if immedok is set", but this appears to be an error.

       X/Open defines no error conditions.  In this  implementation,  functions  using  a  window
       pointer parameter return an error if it is null.


       Note that erase, werase, clear, wclear, clrtobot, and clrtoeol may be macros.


       These functions are described in the XSI Curses standard, Issue 4.  The standard specifies
       that they return ERR on failure, but specifies no error conditions.

       Some historic curses implementations had, as an undocumented feature, the  ability  to  do
       the  equivalent of clearok(..., 1) by saying touchwin(stdscr) or clear(stdscr).  This will
       not work under ncurses.

       This implementation, and others such as Solaris, sets the current position  to  0,0  after
       erasing  via werase and wclear.  That fact is not documented 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.


       ncurses(3NCURSES), outopts(3NCURSES), refresh(3NCURSES), curses_variables(3NCURSES)