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Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

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Section: Miscellaneous Library Functions (3X)
Index Return to Main Contents


addch, waddch, mvaddch, mvwaddch, echochar, wechochar - add a character (with attributes) to a curses window, then advance the cursor  


#include <curses.h>

int addch(const chtype ch);
int waddch(WINDOW *win, const chtype ch);
int mvaddch(int y, int x, const chtype ch);
int mvwaddch(WINDOW *win, int y, int x, const chtype ch);
int echochar(const chtype ch);
int wechochar(WINDOW *win, const chtype ch);



Adding characters

The addch, waddch, mvaddch and mvwaddch routines put the character ch into the given window at its current window position, which is then advanced. They are analogous to putchar in stdio(3). If the advance is at the right margin:
The cursor automatically wraps to the beginning of the next line.
At the bottom of the current scrolling region, and if scrollok is enabled, the scrolling region is scrolled up one line.
If scrollok is not enabled, writing a character at the lower right margin succeeds. However, an error is returned because it is not possible to wrap to a new line

If ch is a tab, newline, carriage return or backspace, the cursor is moved appropriately within the window:

Backspace moves the cursor one character left; at the left edge of a window it does nothing.
Carriage return moves the cursor to the window left margin on the current line.
Newline does a clrtoeol, then moves the cursor to the window left margin on the next line, scrolling the window if on the last line.
Tabs are considered to be at every eighth column. The tab interval may be altered by setting the TABSIZE variable.

If ch is any other control character, it is drawn in ^X notation. Calling winch after adding a control character does not return the character itself, but instead returns the ^-representation of the control character.

Video attributes can be combined with a character argument passed to addch or related functions by logical-ORing them into the character. (Thus, text, including attributes, can be copied from one place to another using inch and addch.) See the curs_attr(3X) page for values of predefined video attribute constants that can be usefully OR'ed into characters.  

Echoing characters

The echochar and wechochar routines are equivalent to a call to addch followed by a call to refresh, or a call to waddch followed by a call to wrefresh. The knowledge that only a single character is being output is used and, for non-control characters, a considerable performance gain may be seen by using these routines instead of their equivalents.  

Line Graphics

The following variables may be used to add line drawing characters to the screen with routines of the addch family. The default character listed below is used if the acsc capability does not define a terminal-specific replacement for it. The names are taken from VT100 nomenclature.


ACS_BOARD#board of squares
ACS_BTEE+bottom tee
ACS_CKBOARD:checker board (stipple)
ACS_DARROWvarrow pointing down
ACS_DEGREE'degree symbol
ACS_HLINE-horizontal line
ACS_LANTERN#lantern symbol
ACS_LARROW<arrow pointing left
ACS_LLCORNER+lower left-hand corner
ACS_LRCORNER+lower right-hand corner
ACS_LTEE+left tee
ACS_PI*greek pi
ACS_RARROW>arrow pointing right
ACS_RTEE+right tee
ACS_S1-scan line 1
ACS_S3-scan line 3
ACS_S7-scan line 7
ACS_S9_scan line 9
ACS_STERLINGfpound-sterling symbol
ACS_TTEE+top tee
ACS_UARROW^arrow pointing up
ACS_ULCORNER+upper left-hand corner
ACS_URCORNER+upper right-hand corner
ACS_VLINE|vertical line


All routines return the integer ERR upon failure and OK on success (the SVr4 manuals specify only "an integer value other than ERR") upon successful completion, unless otherwise noted in the preceding routine descriptions.

Functions with a "mv" prefix first perform a cursor movement using wmove, and return an error if the position is outside the window, or if the window pointer is null.  


Note that addch, mvaddch, mvwaddch, and echochar may be macros.  


All these functions are described in the XSI Curses standard, Issue 4. The defaults specified for forms-drawing characters apply in the POSIX locale.

X/Open Curses states that the ACS_ definitions are char constants. For the wide-character implementation (see curs_add_wch), there are analogous WACS_ definitions which are cchar_t constants.

Some ACS symbols (ACS_S3, ACS_S7, ACS_LEQUAL, ACS_GEQUAL, ACS_PI, ACS_NEQUAL, ACS_STERLING) were not documented in any publicly released System V. However, many publicly available terminfos include acsc strings in which their key characters (pryz{|}) are embedded, and a second-hand list of their character descriptions has come to light. The ACS-prefixed names for them were invented for ncurses(3X).

The TABSIZE variable is implemented in some versions of curses, but is not part of X/Open curses.

If ch is a carriage return, the cursor is moved to the beginning of the current row of the window. This is true of other implementations, but is not documented.  


curses(3X), curs_attr(3X), curs_clear(3X), curs_inch(3X), curs_outopts(3X), curs_refresh(3X), curs_variables(3X), putc(3).

Comparable functions in the wide-character (ncursesw) library are described in curs_add_wch(3X).



Adding characters
Echoing characters
Line Graphics

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