DOKK / manpages / debian 10 / ncurses-doc / curses_variables.3ncurses.en
curses_variables(3NCURSES) curses_variables(3NCURSES)

COLORS, COLOR_PAIRS, COLS, ESCDELAY, LINES, TABSIZE, curscr, newscr, stdscr - curses global variables

#include <curses.h>
int COLOR_PAIRS;


int COLORS;


int COLS;


int ESCDELAY;


int LINES;


int TABSIZE;


WINDOW * curscr;


WINDOW * newscr;


WINDOW * stdscr;

This page summarizes variables provided by the curses library. A more complete description is given in the curses(3X) manual page.

Depending on the configuration, these may be actual variables, or macros (see threads(3NCURSES) and opaque(3NCURSES)) which provide read-only access to curses's state. In either case, applications should treat them as read-only to avoid confusing the library.

After initializing curses, this variable contains the number of color pairs which the terminal can support. Usually the number of color pairs will be the product COLORS*COLORS, however this is not always true:

  • a few terminals use HLS colors, which do not follow this rule
  • terminals supporting a large number of colors are limited by the number of color pairs that can be represented in a signed short value.

After initializing curses, this variable contains the number of colors which the terminal can support.

After initializing curses, this variable contains the width of the screen, i.e., the number of columns.

This variable holds the number of milliseconds to wait after reading an escape character, to distinguish between an individual escape character entered on the keyboard from escape sequences sent by cursor- and function-keys (see curses(3X)).

After initializing curses, this variable contains the height of the screen, i.e., the number of lines.

This variable holds the number of columns used by the curses library when converting a tab character to spaces as it adds the tab to a window (see curs_addch(3X).

This implementation of curses uses a special window curscr to record its updates to the terminal screen.

This is referred to as the “physical screen” in the refresh(3NCURSES) and outopts(3NCURSES) manual pages.

This implementation of curses uses a special window newscr to hold updates to the terminal screen before applying them to curscr.

This is referred to as the “virtual screen” in the kernel(3NCURSES), refresh(3NCURSES) and outopts(3NCURSES) manual pages.

Upon initializing curses, a default window called stdscr, which is the size of the terminal screen, is created. Many curses functions use this window.

The curses library is initialized using either initscr(3X), or newterm(3X).

If curses is configured to use separate curses/terminfo libraries, most of these variables reside in the curses library.

ESCDELAY and TABSIZE are extensions, not provided in most other implementations of curses.

ESCDELAY is an extension in AIX curses:

  • In AIX, the units for ESCDELAY are fifths of a millisecond.
  • The default value for AIX's ESCDELAY is 0.1 seconds.
  • AIX also enforces a limit of 10,000 seconds for ESCDELAY; this implementation currently has no upper limit.

This implementation has long used ESCDELAY with units of milliseconds, making it impossible to be completely compatible with AIX. Likewise, most users have either decided to override the value, or rely upon its default value.

ncurses(3NCURSES), opaque(3NCURSES), terminfo(3NCURSES), threads(3NCURSES), terminfo_variables(3NCURSES), terminfo(5).