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.
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
· 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
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).
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_refresh(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_kernel(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 functions
use this window.
TABSIZE is a feature of SVr4 curses which is not documented by X/Open
· In SVr4 curses, TABSIZE is initially set from the terminal
description's init_tabs capability. After that, it can be
altered 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 description's
it (init_tabs) capability for computing hardware tabs (i.e., tab
stops on the physical screen).
· Other implementations differ. For instance, NetBSD curses allows
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 updating
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
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.
This page is part of the ncurses (new curses) project. Information
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
firstname.lastname@example.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2020-07-14. (At that
time, the date of the most recent commit that was found in the repos‐
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