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NAME | SYNOPSIS | DESCRIPTION | NOTES | PORTABILITY | SEE ALSO | COLOPHON |
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curs_variables(3X) curs_variables(3X)
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 curs_threads(3X) and curs_opaque(3X)) which provide
read-only access to curses's state. In either case, applications
should treat them as read-only to avoid confusing the library.
COLOR_PAIRS
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.
COLORS
After initializing curses, this variable contains the number of
colors which the terminal can support.
COLS
After initializing curses, this variable contains the width of the
screen, i.e., the number of columns.
ESCDELAY
This variable holds the number of milliseconds to wait after read‐
ing an escape character, to distinguish between an individual es‐
cape character entered on the keyboard from escape sequences sent
by cursor- and function-keys (see curses(3X)).
LINES
After initializing curses, this variable contains the height of
the screen, i.e., the number of lines.
TABSIZE
This variable holds the number of columns used by the curses li‐
brary when converting a tab character to spaces as it adds the tab
to a window (see curs_addch(3X).
The Current Screen
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 curs_re‐
fresh(3X) and curs_outopts(3X) manual pages.
The New Screen
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 curs_ker‐
nel(3X), curs_refresh(3X) and curs_outopts(3X) manual pages.
The Standard Screen
Upon initializing curses, a default window called stdscr, which is
the size of the terminal screen, is created. Many curses func‐
tions 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.
TABSIZE is a feature of SVr4 curses which is not documented by
X/Open curses.
• In SVr4 curses, TABSIZE is initially set from the terminal de‐
scription's init_tabs capability. After that, it can be al‐
tered by the applications using SVr4 curses.
SVr4 curses uses the current value of TABSIZE to compute the
position of tabstops for updating both the virtual screen with
addch(3X) as well as the physical screen with mvcur(3X).
• This implementation uses the current value of TABSIZE only for
updating the virtual screen. It uses the terminal descrip‐
tion's it (init_tabs) capability for computing hardware tabs
(i.e., tab stops on the physical screen).
• Other implementations differ. For instance, NetBSD curses al‐
lows TABSIZE to be set through an environment variable. This
implementation does not.
NetBSD curses does not support hardware tabs; it uses the
init_tabs capability and the TABSIZE variable only for updat‐
ing the virtual screen.
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 millisec‐
onds, 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.
curses(3X), curs_opaque(3X), curs_terminfo(3X), curs_threads(3X),
term_variables(3X), terminfo(5).
This page is part of the ncurses (new curses) project. Informa‐
tion about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
bug-ncurses-request@gnu.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
curs_variables(3X)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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