Provided by: ncurses-doc_6.5+20251123-1_all 
NAME
ncurses - character-cell terminal interface with optimized output
SYNOPSIS
#include <curses.h>
DESCRIPTION
The “new curses” library offers the programmer a terminal-independent means of reading keyboard and mouse
input and writing to character-cell displays with output optimized to minimize screen updates. ncurses
replaces the curses libraries from System V Release 4 Unix (“SVr4”) and 4.4BSD Unix, the development of
which ceased in the 1990s. This document describes ncurses version 6.5 (patch 20251123).
ncurses permits control of the terminal screen's contents; abstraction and subdivision thereof with
windows and pads; acquisition of keyboard and mouse events; selection of color and rendering attributes
(such as bold or underline); the definition and use of soft label keys; access to the terminfo terminal
capability database; a termcap compatibility interface; and an abstraction of the system's API for
manipulating the terminal (such as termios(3)).
ncurses implements the interface described by X/Open Curses Issue 7. In many behavioral details not
standardized by X/Open, ncurses emulates the curses library of SVr4 and provides numerous useful
extensions.
ncurses man pages employ several sections to clarify matters of usage and interoperability with other
curses implementations.
• “NOTES” describes issues and caveats of which any user of the ncurses API should be aware, such as
limitations on the size of an underlying integral type or the availability of a preprocessor macro
exclusive of a function definition (which prevents its address from being taken). This section also
describes implementation details of significance to the programmer but which are not standardized.
• “EXTENSIONS” presents ncurses innovations beyond the X/Open Curses standard and/or the SVr4 curses
implementation. They are termed extensions to indicate that they cannot be implemented solely by
using the library API, but require access to the library's internal state.
• “PORTABILITY” discusses matters (beyond the exercise of extensions) that should be considered when
writing to a curses standard, or for multiple implementations.
• “HISTORY” examines points of detail in ncurses and other curses implementations over the decades of
their development, particularly where precedent or inertia have frustrated better design (and, in a
few cases, where such inertia has been overcome).
A curses application must be linked with the library; use the -lncurses option to your compiler or
linker. A debugging version of the library may be available; if so, link with it using -lncurses_g.
(Your system integrator may have installed these libraries such that you can use the options -lcurses and
-lcurses_g, respectively.) The ncurses_g library logs events describing ncurses actions to a file called
trace in the application's working directory at startup. See section “ALTERNATE CONFIGURATIONS” below.
Application Structure
A curses application uses information from the system locale; setlocale(3) prepares it for curses library
calls.
setlocale(LC_ALL, "");
If the locale is not thus initialized, the library assumes that characters are printable as in
ISO 8859-1, to work with certain legacy programs. You should initialize the locale; do not expect
consistent behavior from the library when the locale has not been set up.
initscr(3NCURSES) or newterm(3NCURSES) must be called to initialize curses before use of any functions
that access or manipulate windows or screens.
To get character-at-a-time input without echoing — most interactive, screen-oriented programs want this —
use the following sequence.
initscr(); cbreak(); noecho();
Most applications would perform further setup as follows.
noqiflush();
keypad(stdscr, TRUE);
A curses program then often enters an event-handling loop. Call endwin(3NCURSES) before exiting.
Overview
A curses library abstracts the terminal with a SCREEN data structure, and represents all or part of its
display with WINDOW structures. Distinct properties apply to each; for example, the line discipline of a
typical Unix terminal driver is in one of three modes: raw, cbreak, or canonical (“cooked”). In curses,
the line discipline is a property of the screen, applying identically to all windows associated with it.
A window is a rectangular grid of character cells, addressed by line and column coordinates (y, x), with
the upper left corner as (0, 0). A window called stdscr, by default the same size as the terminal
screen, is always available. Create others with newwin(3NCURSES).
A curses library does not manage overlapping windows (but see below). You can either use stdscr to
manage one screen-filling window, or tile the screen into non-overlapping windows and not use stdscr at
all. Mixing the two approaches will result in unpredictable and undesired effects.
Functions permit manipulation of a window and the cursor identifying the cell within it at which the next
operation will occur. Among those, the most basic are move(3NCURSES) and addch(3NCURSES): these place
the cursor within and write a character to stdscr, respectively.
Frequent changes to the terminal screen can cause unpleasant flicker or inefficient use of the
communication channel to the device, so as a rule the library does not update it automatically.
Therefore, after using curses functions to accumulate a set of desired updates that make sense to present
together, call refresh(3NCURSES) to tell the library to make the user's screen look like stdscr. The
library optimizes its output by computing a minimal volume of operations to mutate the screen from its
state at the previous refresh to the new one. Effective optimization demands accurate information about
the terminal device: the management of such information is the province of the terminfo(3NCURSES) API, a
feature of every standard curses implementation.
Special windows called pads may also be manipulated. These are not constrained to the size of the
terminal screen and their contents need not be completely displayed. See pad(3NCURSES).
Many terminals support configuration of character cell foreground and background colors as well as
attributes, which cause characters to render in such modes as boldfaced, underlined, or in reverse video.
See color(3NCURSES) and attr(3NCURSES).
curses defines constants to simplify access to a small set of forms-drawing graphics corresponding to the
DEC Alternate Character Set (ACS), a feature of VT100 and other terminals. See addch(3NCURSES).
curses is implemented using the operating system's terminal driver; key events are received not as scan
codes but as byte sequences. The driver reports graphical keycaps (alphanumeric and punctuation keys,
and the space) as-is. Everything else, including the tab, enter/return, keypad, arrow, and function
keys, appears to curses as a control character or a multibyte escape sequence. curses can translate the
latter into unique key codes. See keypad(3NCURSES) and getch(3NCURSES).
ncurses provides reimplementations of the SVr4 panel(3NCURSES), form(3FORM), and menu(3MENU) libraries;
they permit overlapping windows and ease construction of user interfaces with curses.
Initialization
The selection of an appropriate value of TERM in the process environment is essential to correct curses
and terminfo library operation. A well-configured system selects a correct TERM value automatically;
tset(1) may assist with troubleshooting exotic situations.
If you change the terminal type from a shell, export TERM, then run tset(1) or the “tput init” command.
See subsection “Tabs and Initialization” of terminfo(5).
If the environment variables LINES and COLUMNS are set, or if the curses program is executing in a
graphical windowing environment, the information obtained thence overrides that obtained by terminfo. An
ncurses extension supports resizable terminal displays; see wresize(3NCURSES).
If the environment variable TERMINFO is defined, a curses program checks first for a terminal type
description in the location it identifies. TERMINFO is useful for developing type descriptions or when
write permission to /etc/terminfo is not available.
See section “ENVIRONMENT” below.
Naming Conventions
curses offers many functions in variant forms using a regular set of alternatives to the name of an
elemental one. Those prefixed with “w” require a WINDOW pointer argument; those with a “mv” prefix first
perform cursor movement using wmove(3NCURSES); a “mvw” prefix indicates both. The “w” function is
typically the elemental one; the removal of this prefix usually indicates operation on stdscr.
Four functions prefixed with “p” require a pad argument; see below.
In function synopses, ncurses man pages apply the following names to parameters. We introduce the
character types in the next subsection.
bf a bool (TRUE or FALSE)
c a char or int
ch a chtype
wc a wchar_t or wint_t
wch a cchar_t
win pointer to a WINDOW
pad pointer to a WINDOW that is a pad
pair a foreground/background color pair identifier
Wide and Non-wide Character Configurations
This man page primarily surveys functions that appear in any configuration of the library. There are two
common configurations; for others, see section “ALTERNATE CONFIGURATIONS” below.
ncurses is the library in its “non-wide” configuration, handling only eight-bit characters. It stores
a character combined with attributes and a color pair identifier in a chtype datum, which is
often an alias of int. A string of curses characters is similar to a C char string; a chtype
string ends with an integral 0, the null curses character.
Attributes and a color pair identifier (with no corresponding character) can be stored in
variables of chtype or attr_t type. In either case, they are accessed via an integral bit
mask.
ncurses stores each cell of a WINDOW as a chtype. X/Open Curses does not specify the sizes of
the character code or color pair identifier, nor the quantity of attribute bits, in chtype;
these are implementation-dependent. ncurses uses eight bits for the character code. An
application requiring a wider character type, for instance to represent Unicode, should use the
wide-character API.
ncursesw is the library in its “wide” configuration, which handles character encodings requiring a
larger data type than char (a byte-sized type) can represent. It provides additional functions
that complement those in the non-wide library where the size of the underlying character type
is significant. A somewhat regular naming convention relates many of the wide variants to
their non-wide counterparts; where a non-wide function name contains “ch” or “str”, prefix it
with “_w” to obtain the wide counterpart. For example, waddch becomes wadd_wch. An exception
is ins_nwstr (and its variants), spelled thus instead of “insn_wstr”. (Exceptions that add
only “w” comprise addwstr, inwstr, and their variants.)
This convention is inapplicable to some non-wide function names, so other transformations are
used for the wide configuration: the window background management function “bkgd” becomes
“bkgrnd”; the window border-drawing and -clearing functions are suffixed with “_set”; and
character attribute manipulation functions like “attron” become “attr_on”.
cchar_t is a curses complex character and corresponds to the non-wide-character
configuration's chtype. It is a structure type because it requires more storage than
a standard scalar type offers. A character code may not be representable as a char,
and moreover more than one character may occupy a cell (as with accent marks and other
diacritics). Each character is of type wchar_t; a complex character contains one
spacing character and zero or more non-spacing characters (see below). A string of
complex characters ends with a cchar_t whose wchar_t member is the null wide
character. Attributes and a color pair identifier are stored in separate fields of
the structure, not combined into an integer as in chtype.
ncurses stores each cell of a WINDOW as a cchar_t. setcchar(3NCURSES) and getcchar(3NCURSES)
store and retrieve cchar_t data.
The wide library API of ncurses depends on two data types standardized by ISO C95.
wchar_t stores a wide character. Like chtype, it may be an alias of int. Depending on the
character encoding, a wide character may be spacing, meaning that it occupies a
character cell by itself and typically accompanies cursor advancement, or non-spacing,
meaning that it occupies the same cell as a spacing character, is often regarded as a
“modifier” of the base glyph with which it combines, and typically does not advance
the cursor.
wint_t can store a wchar_t or the constant WEOF, analogously to the int-sized character
manipulation functions of ISO C and its constant EOF.
Function Name Index
The following table lists the curses functions provided in the non-wide and wide APIs and the
corresponding man pages that describe them. Those flagged with “*” are ncurses-specific, neither
described by X/Open Curses nor present in SVr4.
curses Function Name Man Page
───────────────────────────────────────────────────
COLOR_PAIR color(3NCURSES)
PAIR_NUMBER color(3NCURSES)
add_wch add_wch(3NCURSES)
add_wchnstr add_wchstr(3NCURSES)
add_wchstr add_wchstr(3NCURSES)
addch addch(3NCURSES)
addchnstr addchstr(3NCURSES)
addchstr addchstr(3NCURSES)
addnstr addstr(3NCURSES)
addnwstr addwstr(3NCURSES)
addstr addstr(3NCURSES)
addwstr addwstr(3NCURSES)
alloc_pair new_pair(3NCURSES)*
assume_default_colors default_colors(3NCURSES)*
attr_get attr(3NCURSES)
attr_off attr(3NCURSES)
attr_on attr(3NCURSES)
attr_set attr(3NCURSES)
attroff attr(3NCURSES)
attron attr(3NCURSES)
attrset attr(3NCURSES)
baudrate termattrs(3NCURSES)
beep beep(3NCURSES)
bkgd bkgd(3NCURSES)
bkgdset bkgd(3NCURSES)
bkgrnd bkgrnd(3NCURSES)
bkgrndset bkgrnd(3NCURSES)
border border(3NCURSES)
border_set border_set(3NCURSES)
box border(3NCURSES)
box_set border_set(3NCURSES)
can_change_color color(3NCURSES)
cbreak inopts(3NCURSES)
chgat attr(3NCURSES)
clear clear(3NCURSES)
clearok outopts(3NCURSES)
clrtobot clear(3NCURSES)
clrtoeol clear(3NCURSES)
color_content color(3NCURSES)
color_set attr(3NCURSES)
copywin overlay(3NCURSES)
curs_set kernel(3NCURSES)
curses_trace trace(3NCURSES)*
curses_version extensions(3NCURSES)*
def_prog_mode kernel(3NCURSES)
def_shell_mode kernel(3NCURSES)
define_key define_key(3NCURSES)*
del_curterm terminfo(3NCURSES)
delay_output util(3NCURSES)
delch delch(3NCURSES)
deleteln deleteln(3NCURSES)
delscreen initscr(3NCURSES)
delwin window(3NCURSES)
derwin window(3NCURSES)
doupdate refresh(3NCURSES)
dupwin window(3NCURSES)
echo inopts(3NCURSES)
echo_wchar add_wch(3NCURSES)
echochar addch(3NCURSES)
endwin initscr(3NCURSES)
erase clear(3NCURSES)
erasechar termattrs(3NCURSES)
erasewchar termattrs(3NCURSES)
exit_curses memleaks(3NCURSES)*
exit_terminfo memleaks(3NCURSES)*
extended_color_content color(3NCURSES)*
extended_pair_content color(3NCURSES)*
extended_slk_color slk(3NCURSES)*
filter util(3NCURSES)
find_pair new_pair(3NCURSES)*
flash beep(3NCURSES)
flushinp util(3NCURSES)
free_pair new_pair(3NCURSES)*
get_escdelay threads(3NCURSES)*
get_wch get_wch(3NCURSES)
get_wstr get_wstr(3NCURSES)
getattrs attr(3NCURSES)
getbegx legacy(3NCURSES)*
getbegy legacy(3NCURSES)*
getbegyx getyx(3NCURSES)
getbkgd bkgd(3NCURSES)
getbkgrnd bkgrnd(3NCURSES)
getcchar getcchar(3NCURSES)
getch getch(3NCURSES)
getcurx legacy(3NCURSES)*
getcury legacy(3NCURSES)*
getmaxx legacy(3NCURSES)*
getmaxy legacy(3NCURSES)*
getmaxyx getyx(3NCURSES)
getmouse mouse(3NCURSES)*
getn_wstr get_wstr(3NCURSES)
getnstr getstr(3NCURSES)
getparx legacy(3NCURSES)*
getpary legacy(3NCURSES)*
getparyx getyx(3NCURSES)
getstr getstr(3NCURSES)
getsyx kernel(3NCURSES)
getwin util(3NCURSES)
getyx getyx(3NCURSES)
halfdelay inopts(3NCURSES)
has_colors color(3NCURSES)
has_ic termattrs(3NCURSES)
has_il termattrs(3NCURSES)
has_key getch(3NCURSES)*
has_mouse mouse(3NCURSES)*
hline border(3NCURSES)
hline_set border_set(3NCURSES)
idcok outopts(3NCURSES)
idlok outopts(3NCURSES)
immedok outopts(3NCURSES)
in_wch in_wch(3NCURSES)
in_wchnstr in_wchstr(3NCURSES)
in_wchstr in_wchstr(3NCURSES)
inch inch(3NCURSES)
inchnstr inchstr(3NCURSES)
inchstr inchstr(3NCURSES)
init_color color(3NCURSES)
init_extended_color color(3NCURSES)*
init_extended_pair color(3NCURSES)*
init_pair color(3NCURSES)
initscr initscr(3NCURSES)
innstr instr(3NCURSES)
innwstr inwstr(3NCURSES)
ins_nwstr ins_wstr(3NCURSES)
ins_wch ins_wch(3NCURSES)
ins_wstr ins_wstr(3NCURSES)
insch insch(3NCURSES)
insdelln deleteln(3NCURSES)
insertln deleteln(3NCURSES)
insnstr insstr(3NCURSES)
insstr insstr(3NCURSES)
instr instr(3NCURSES)
intrflush inopts(3NCURSES)
inwstr inwstr(3NCURSES)
is_cbreak inopts(3NCURSES)*
is_cleared opaque(3NCURSES)*
is_echo inopts(3NCURSES)*
is_idcok opaque(3NCURSES)*
is_idlok opaque(3NCURSES)*
is_immedok opaque(3NCURSES)*
is_keypad opaque(3NCURSES)*
is_leaveok opaque(3NCURSES)*
is_linetouched touch(3NCURSES)
is_nl inopts(3NCURSES)*
is_nodelay opaque(3NCURSES)*
is_notimeout opaque(3NCURSES)*
is_pad opaque(3NCURSES)*
is_raw inopts(3NCURSES)*
is_scrollok opaque(3NCURSES)*
is_subwin opaque(3NCURSES)*
is_syncok opaque(3NCURSES)*
is_term_resized resizeterm(3NCURSES)*
is_wintouched touch(3NCURSES)
isendwin initscr(3NCURSES)
key_defined key_defined(3NCURSES)*
key_name util(3NCURSES)
keybound keybound(3NCURSES)*
keyname util(3NCURSES)
keyok keyok(3NCURSES)*
keypad inopts(3NCURSES)
killchar termattrs(3NCURSES)
killwchar termattrs(3NCURSES)
leaveok outopts(3NCURSES)
longname termattrs(3NCURSES)
mcprint print(3NCURSES)*
meta inopts(3NCURSES)
mouse_trafo mouse(3NCURSES)*
mouseinterval mouse(3NCURSES)*
mousemask mouse(3NCURSES)*
move move(3NCURSES)
mvadd_wch add_wch(3NCURSES)
mvadd_wchnstr add_wchstr(3NCURSES)
mvadd_wchstr add_wchstr(3NCURSES)
mvaddch addch(3NCURSES)
mvaddchnstr addchstr(3NCURSES)
mvaddchstr addchstr(3NCURSES)
mvaddnstr addstr(3NCURSES)
mvaddnwstr addwstr(3NCURSES)
mvaddstr addstr(3NCURSES)
mvaddwstr addwstr(3NCURSES)
mvchgat attr(3NCURSES)
mvcur kernel(3NCURSES)
mvdelch delch(3NCURSES)
mvderwin window(3NCURSES)
mvget_wch get_wch(3NCURSES)
mvget_wstr get_wstr(3NCURSES)
mvgetch getch(3NCURSES)
mvgetn_wstr get_wstr(3NCURSES)
mvgetnstr getstr(3NCURSES)
mvgetstr getstr(3NCURSES)
mvhline border(3NCURSES)
mvhline_set border_set(3NCURSES)
mvin_wch in_wch(3NCURSES)
mvin_wchnstr in_wchstr(3NCURSES)
mvin_wchstr in_wchstr(3NCURSES)
mvinch inch(3NCURSES)
mvinchnstr inchstr(3NCURSES)
mvinchstr inchstr(3NCURSES)
mvinnstr instr(3NCURSES)
mvinnwstr inwstr(3NCURSES)
mvins_nwstr ins_wstr(3NCURSES)
mvins_wch ins_wch(3NCURSES)
mvins_wstr ins_wstr(3NCURSES)
mvinsch insch(3NCURSES)
mvinsnstr insstr(3NCURSES)
mvinsstr insstr(3NCURSES)
mvinstr instr(3NCURSES)
mvinwstr inwstr(3NCURSES)
mvprintw printw(3NCURSES)
mvscanw scanw(3NCURSES)
mvvline border(3NCURSES)
mvvline_set border_set(3NCURSES)
mvwadd_wch add_wch(3NCURSES)
mvwadd_wchnstr add_wchstr(3NCURSES)
mvwadd_wchstr add_wchstr(3NCURSES)
mvwaddch addch(3NCURSES)
mvwaddchnstr addchstr(3NCURSES)
mvwaddchstr addchstr(3NCURSES)
mvwaddnstr addstr(3NCURSES)
mvwaddnwstr addwstr(3NCURSES)
mvwaddstr addstr(3NCURSES)
mvwaddwstr addwstr(3NCURSES)
mvwchgat attr(3NCURSES)
mvwdelch delch(3NCURSES)
mvwget_wch get_wch(3NCURSES)
mvwget_wstr get_wstr(3NCURSES)
mvwgetch getch(3NCURSES)
mvwgetn_wstr get_wstr(3NCURSES)
mvwgetnstr getstr(3NCURSES)
mvwgetstr getstr(3NCURSES)
mvwhline border(3NCURSES)
mvwhline_set border_set(3NCURSES)
mvwin window(3NCURSES)
mvwin_wch in_wch(3NCURSES)
mvwin_wchnstr in_wchstr(3NCURSES)
mvwin_wchstr in_wchstr(3NCURSES)
mvwinch inch(3NCURSES)
mvwinchnstr inchstr(3NCURSES)
mvwinchstr inchstr(3NCURSES)
mvwinnstr instr(3NCURSES)
mvwinnwstr inwstr(3NCURSES)
mvwins_nwstr ins_wstr(3NCURSES)
mvwins_wch ins_wch(3NCURSES)
mvwins_wstr ins_wstr(3NCURSES)
mvwinsch insch(3NCURSES)
mvwinsnstr insstr(3NCURSES)
mvwinsstr insstr(3NCURSES)
mvwinstr instr(3NCURSES)
mvwinwstr inwstr(3NCURSES)
mvwprintw printw(3NCURSES)
mvwscanw scanw(3NCURSES)
mvwvline border(3NCURSES)
mvwvline_set border_set(3NCURSES)
napms kernel(3NCURSES)
newpad pad(3NCURSES)
newterm initscr(3NCURSES)
newwin window(3NCURSES)
nl inopts(3NCURSES)
nocbreak inopts(3NCURSES)
nodelay inopts(3NCURSES)
noecho inopts(3NCURSES)
nofilter util(3NCURSES)*
nonl inopts(3NCURSES)
noqiflush inopts(3NCURSES)
noraw inopts(3NCURSES)
notimeout inopts(3NCURSES)
overlay overlay(3NCURSES)
overwrite overlay(3NCURSES)
pair_content color(3NCURSES)
pecho_wchar pad(3NCURSES)
pechochar pad(3NCURSES)
pnoutrefresh pad(3NCURSES)
prefresh pad(3NCURSES)
printw printw(3NCURSES)
putp terminfo(3NCURSES)
putwin util(3NCURSES)
qiflush inopts(3NCURSES)
raw inopts(3NCURSES)
redrawwin refresh(3NCURSES)
refresh refresh(3NCURSES)
reset_color_pairs color(3NCURSES)*
reset_prog_mode kernel(3NCURSES)
reset_shell_mode kernel(3NCURSES)
resetty kernel(3NCURSES)
resize_term resizeterm(3NCURSES)*
resizeterm resizeterm(3NCURSES)*
restartterm terminfo(3NCURSES)
ripoffline kernel(3NCURSES)
savetty kernel(3NCURSES)
scanw scanw(3NCURSES)
scr_dump scr_dump(3NCURSES)
scr_init scr_dump(3NCURSES)
scr_restore scr_dump(3NCURSES)
scr_set scr_dump(3NCURSES)
scrl scroll(3NCURSES)
scroll scroll(3NCURSES)
scrollok outopts(3NCURSES)
set_curterm terminfo(3NCURSES)
set_escdelay threads(3NCURSES)*
set_tabsize threads(3NCURSES)*
set_term initscr(3NCURSES)
setcchar getcchar(3NCURSES)
setscrreg outopts(3NCURSES)
setsyx kernel(3NCURSES)
setupterm terminfo(3NCURSES)
slk_attr slk(3NCURSES)*
slk_attr_off slk(3NCURSES)
slk_attr_on slk(3NCURSES)
slk_attr_set slk(3NCURSES)
slk_attroff slk(3NCURSES)
slk_attron slk(3NCURSES)
slk_attrset slk(3NCURSES)
slk_clear slk(3NCURSES)
slk_color slk(3NCURSES)
slk_init slk(3NCURSES)
slk_label slk(3NCURSES)
slk_noutrefresh slk(3NCURSES)
slk_refresh slk(3NCURSES)
slk_restore slk(3NCURSES)
slk_set slk(3NCURSES)
slk_touch slk(3NCURSES)
slk_wset slk(3NCURSES)
standend attr(3NCURSES)
standout attr(3NCURSES)
start_color color(3NCURSES)
subpad pad(3NCURSES)
subwin window(3NCURSES)
syncok window(3NCURSES)
term_attrs termattrs(3NCURSES)
termattrs termattrs(3NCURSES)
termname termattrs(3NCURSES)
tgetent termcap(3NCURSES)
tgetflag termcap(3NCURSES)
tgetnum termcap(3NCURSES)
tgetstr termcap(3NCURSES)
tgoto termcap(3NCURSES)
tigetflag terminfo(3NCURSES)
tigetnum terminfo(3NCURSES)
tigetstr terminfo(3NCURSES)
timeout inopts(3NCURSES)
tiparm terminfo(3NCURSES)
tiparm_s terminfo(3NCURSES)*
tiscan_s terminfo(3NCURSES)*
touchline touch(3NCURSES)
touchwin touch(3NCURSES)
tparm terminfo(3NCURSES)
tputs termcap(3NCURSES)
tputs terminfo(3NCURSES)
trace trace(3NCURSES)*
typeahead inopts(3NCURSES)
unctrl util(3NCURSES)
unget_wch get_wch(3NCURSES)
ungetch getch(3NCURSES)
ungetmouse mouse(3NCURSES)*
untouchwin touch(3NCURSES)
use_default_colors default_colors(3NCURSES)*
use_env util(3NCURSES)
use_extended_names extensions(3NCURSES)*
use_legacy_coding legacy_coding(3NCURSES)*
use_screen threads(3NCURSES)*
use_tioctl util(3NCURSES)*
use_window threads(3NCURSES)*
vid_attr terminfo(3NCURSES)
vid_puts terminfo(3NCURSES)
vidattr terminfo(3NCURSES)
vidputs terminfo(3NCURSES)
vline border(3NCURSES)
vline_set border_set(3NCURSES)
vw_printw printw(3NCURSES)
vw_scanw scanw(3NCURSES)
vwprintw printw(3NCURSES)
vwscanw scanw(3NCURSES)
wadd_wch add_wch(3NCURSES)
wadd_wchnstr add_wchstr(3NCURSES)
wadd_wchstr add_wchstr(3NCURSES)
waddch addch(3NCURSES)
waddchnstr addchstr(3NCURSES)
waddchstr addchstr(3NCURSES)
waddnstr addstr(3NCURSES)
waddnwstr addwstr(3NCURSES)
waddstr addstr(3NCURSES)
waddwstr addwstr(3NCURSES)
wattr_get attr(3NCURSES)
wattr_off attr(3NCURSES)
wattr_on attr(3NCURSES)
wattr_set attr(3NCURSES)
wattroff attr(3NCURSES)
wattron attr(3NCURSES)
wattrset attr(3NCURSES)
wbkgd bkgd(3NCURSES)
wbkgdset bkgd(3NCURSES)
wbkgrnd bkgrnd(3NCURSES)
wbkgrndset bkgrnd(3NCURSES)
wborder border(3NCURSES)
wborder_set border_set(3NCURSES)
wchgat attr(3NCURSES)
wclear clear(3NCURSES)
wclrtobot clear(3NCURSES)
wclrtoeol clear(3NCURSES)
wcolor_set attr(3NCURSES)
wcursyncup window(3NCURSES)
wdelch delch(3NCURSES)
wdeleteln deleteln(3NCURSES)
wecho_wchar add_wch(3NCURSES)
wechochar addch(3NCURSES)
wenclose mouse(3NCURSES)*
werase clear(3NCURSES)
wget_wch get_wch(3NCURSES)
wget_wstr get_wstr(3NCURSES)
wgetbkgrnd bkgrnd(3NCURSES)
wgetch getch(3NCURSES)
wgetdelay opaque(3NCURSES)*
wgetn_wstr get_wstr(3NCURSES)
wgetnstr getstr(3NCURSES)
wgetparent opaque(3NCURSES)*
wgetscrreg opaque(3NCURSES)*
wgetstr getstr(3NCURSES)
whline border(3NCURSES)
whline_set border_set(3NCURSES)
win_wch in_wch(3NCURSES)
win_wchnstr in_wchstr(3NCURSES)
win_wchstr in_wchstr(3NCURSES)
winch inch(3NCURSES)
winchnstr inchstr(3NCURSES)
winchstr inchstr(3NCURSES)
winnstr instr(3NCURSES)
winnwstr inwstr(3NCURSES)
wins_nwstr ins_wstr(3NCURSES)
wins_wch ins_wch(3NCURSES)
wins_wstr ins_wstr(3NCURSES)
winsch insch(3NCURSES)
winsdelln deleteln(3NCURSES)
winsertln deleteln(3NCURSES)
winsnstr insstr(3NCURSES)
winsstr insstr(3NCURSES)
winstr instr(3NCURSES)
winwstr inwstr(3NCURSES)
wmouse_trafo mouse(3NCURSES)*
wmove move(3NCURSES)
wnoutrefresh refresh(3NCURSES)
wprintw printw(3NCURSES)
wredrawln refresh(3NCURSES)
wrefresh refresh(3NCURSES)
wresize wresize(3NCURSES)*
wscanw scanw(3NCURSES)
wscrl scroll(3NCURSES)
wsetscrreg outopts(3NCURSES)
wstandend attr(3NCURSES)
wstandout attr(3NCURSES)
wsyncdown window(3NCURSES)
wsyncup window(3NCURSES)
wtimeout inopts(3NCURSES)
wtouchln touch(3NCURSES)
wunctrl util(3NCURSES)
wvline border(3NCURSES)
wvline_set border_set(3NCURSES)
ncurses's screen-pointer extension adds additional functions corresponding to many of the above, each
with an “_sp” suffix; see sp_funcs(3NCURSES).
The availability of some extensions is configurable when ncurses is compiled; see sections “ALTERNATE
CONFIGURATIONS” and “EXTENSIONS” below.
RETURN VALUE
Unless otherwise noted, functions that return integers return the constants OK on success and ERR on
failure; see curses_variables(3NCURSES). Functions that return pointers return a null pointer on
failure. Typically, ncurses treats a null pointer passed as a function parameter as a failure.
Functions prefixed with “mv” first perform cursor movement and fail if the position (y, x) is outside the
window boundaries.
ENVIRONMENT
The following symbols from the process environment customize the runtime behavior of ncurses
applications. The library may be configured to disregard the variables TERMINFO, TERMINFO_DIRS,
TERMPATH, and HOME, if the user is the superuser (root), or the application uses setuid(2) or setgid(2).
BAUDRATE
The debugging library checks this variable when the application has redirected output to a file. ncurses
interprets its integral value as the terminal's line speed in bits per second. If that value is absent
or invalid, ncurses uses 9600. This feature allows developers to construct repeatable test cases that
take into account optimization decisions that depend on the terminal's line speed.
CC (command character)
When set, the command_character (cmdch) capability value of loaded terminfo entries changes to the value
of this variable. Very few terminfo entries provide this feature.
Because this name is also used in development environments to store the C compiler's name, ncurses
ignores its value if it is not one character in length.
COLUMNS
This variable specifies the width of the screen in character cells. Applications running in a windowing
environment usually are able to obtain the width of the window in which they are executing. ncurses
enforces an upper limit of 512 when reading the value. If COLUMNS is not defined and the terminal's
screen size is not available from the terminal driver, ncurses uses the size specified by the columns
(cols) capability of the terminal type's entry in the terminfo database, if any.
It is important that your application use the correct screen size. Automatic detection thereof is not
always possible because an application may be running on a host that does not honor NAWS (Negotiations
About Window Size) or as a different user ID than the owner of the terminal device file. Setting COLUMNS
and/or LINES overrides the library's use of the screen size obtained from the operating system.
The COLUMNS and LINES variables may be specified independently. This property is useful to circumvent
misfeatures of legacy terminal type descriptions; xterm(1) descriptions specifying 65 lines were once
notorious. For best results, avoid specifying cols and lines capability codes in terminfo descriptions
of terminal emulators.
use_env(3NCURSES) can disable use of the process environment in determining the screen size.
use_tioctl(3NCURSES) can update COLUMNS and LINES to match the screen size obtained from system calls or
the terminal database.
ESCDELAY
For curses to distinguish the ESC character resulting from a user's press of the “Escape” key on the
input device from one beginning an escape sequence (as commonly produced by function keys), it waits
after receiving the escape character to see if further characters are available on the input stream
within a short interval. A global variable ESCDELAY stores this interval in milliseconds. The default
value of 1000 (one second) is adequate for most uses. This environment variable overrides it; ncurses
enforces an upper limit of 30,000 (30 seconds) when reading the value.
The most common instance where you may wish to change this value is to work with a remote host over a
slow communication channel. If the host running a curses application does not receive the characters of
an escape sequence in a timely manner, the library can interpret them as multiple key stroke events.
Conversely, a fast typist on a low-latency connection who happens to input an ESC followed by characters
that match an escape sequence may experience confusing application behavior.
xterm(1) mouse events are a form of escape sequence; therefore, if your application makes heavy use of
multiple-clicking, you may wish to lengthen the default value because the delay applies to the composite
multi-click event as well as the individual clicks.
Portable applications should not rely upon the presence of ESCDELAY in either form, but setting the
environment variable rather than the global variable does not create problems when compiling an
application.
If keypad(3NCURSES) is disabled for the curses window receiving input, ESCDELAY is irrelevant and a
program must disambiguate escape sequences itself.
HOME
ncurses may read and write auxiliary terminal descriptions in .termcap and .terminfo files in the user's
home directory.
LINES
This counterpart to COLUMNS specifies the height of the screen in characters. The corresponding terminfo
capability and code is lines. See the description of the COLUMNS variable above.
MOUSE_BUTTONS_123
(OS/2 EMX port only) OS/2 numbers a three-button mouse inconsistently with other platforms, such that 1
is the left button, 2 the right, and 3 the middle. This variable customizes the mouse button numbering.
Its value must be three digits 1-3 in any order. By default, ncurses assumes a numbering of “132”.
NCURSES_ASSUMED_COLORS
If set, this variable overrides the ncurses library's compiled-in assumption that the terminal's default
colors are white on black; see default_colors(3NCURSES). Set the foreground and background color values
with this environment variable by assigning it two integer values separated by a comma, indicating
foregound and background color numbers, respectively.
For example, to tell ncurses not to assume anything about the colors, use a value of “-1,-1”. To make
the default color scheme green on black on a terminal that uses ANSI X3.64/ECMA-48/ISO 6429 color
assignments, use “2,0”. ncurses accepts integral values from -1 up to the value of the terminfo
max_colors (colors) capability for the selected terminal type.
NCURSES_CONSOLE2
(MinGW port only) The Console2 program defectively handles the Microsoft Console API call CreateConsole‐
ScreenBuffer. Applications that use it will hang. However, it is possible to simulate the action of
this call by mapping coordinates, explicitly saving and restoring the original screen contents. Setting
the environment variable NCGDB has the same effect.
NCURSES_GPM_TERMS
(Linux only) When ncurses is configured to use the GPM interface, this variable may list one or more
terminal type names, delimited by vertical bars (|) or colons (:), against which the TERM variable (see
below) is matched. An empty value disables the GPM interface, using ncurses's built-in support for
xterm(1) mouse protocols instead. If the variable is absent, ncurses attempts to open GPM if TERM
contains “linux”.
NCURSES_NO_HARD_TABS
ncurses may use tab characters in cursor movement optimization. In some cases, your terminal driver may
not handle them properly. Set this environment variable to any value to disable the feature. You can
also adjust your stty(1) settings to avoid the problem.
NCURSES_NO_MAGIC_COOKIE
Many terminals store video attributes as properties of a character cell, as curses does. Historically,
some recorded changes in video attributes as data that logically (but invisibly) occupied character cells
on the display, switching attributes on or off, similarly to tags in a markup language, which then had to
be overprinted to depict the cells' desired contents; these are termed “magic cookies”. If the terminfo
entry for your terminal type does not adequately describe its handling of magic cookies, set this
variable to any value to instruct ncurses to disable attributes entirely.
NCURSES_NO_PADDING
Most terminal type descriptions in the terminfo database detail hardware devices. Many people use
curses-based applications in terminal emulator programs that run in a windowing environment. These
programs can duplicate all of the important features of a hardware terminal, but often lack their
limitations. Chief among these absent drawbacks is the problem of data flow management; that is,
limiting the speed of communication to what the hardware could handle. Unless a hardware terminal is
interfaced into a terminal concentrator (which does flow control), an application must manage flow itself
to prevent overruns and data loss.
A solution that comes at no hardware cost is for an application to pause transmission after directing a
terminal to execute an operation that it performs slowly, such as clearing the display. Many terminal
type descriptions, including that for the VT100, embed delay specifications in capabilities. You may
wish to use these terminal descriptions without paying the performance penalty. Set NCURSES_NO_PADDING
to any value to disable all but mandatory padding. Mandatory padding is used by such terminal
capabilities as flash_screen (flash).
NCURSES_NO_SETBUF
(Obsolete) Prior to internal changes developed in ncurses 5.9 (patches 20120825 through 20130126), the
library used setbuf(3) to enable fully buffered output when initializing the terminal. This was done, as
in SVr4 curses, to increase performance. For testing purposes, both of ncurses and of certain
applications, this feature was made optional. Setting this variable disabled output buffering, leaving
the output stream in the original (usually line-buffered) mode.
Nowadays, ncurses performs its own buffering and does not require this workaround; it does not modify the
buffering of the standard output stream. This approach makes the library's handling of keyboard-
initiated signals more robust. A drawback is that certain unconventional programs mixed stdio(3) calls
with ncurses calls and (usually) got the behavior they expected. This is no longer the case; ncurses
does not write to the standard output file descriptor through a stdio-buffered stream.
As a special case, low-level API calls such as putp(3NCURSES) still use the standard output stream.
High-level curses calls such as printw(3NCURSES) do not.
NCURSES_NO_UTF8_ACS
At initialization, ncurses inspects the TERM environment variable for special cases where VT100 forms-
drawing characters (and the corresponding alternate character set terminfo capabilities) are known to be
unsupported by terminal types that otherwise claim VT100 compatibility. Specifically, when running in a
UTF-8 locale, the Linux virtual console device and the GNU screen(1) program ignore them. Set this
variable to a nonzero value to instruct ncurses that the terminal's ACS support is broken; the library
then outputs Unicode code points that correspond to the forms-drawing characters. Set it to zero (or a
non-integer) to disable the special check for terminal type names matching “linux” or “screen”, directing
ncurses to assume that the ACS feature works if the terminal type description advertises it.
As an alternative to use of this variable, ncurses checks for an extended terminfo numeric capability U8
that can be compiled using “tic -x”. Examples follow.
# linux console, if patched to provide working
# VT100 shift-in/shift-out, with corresponding font.
linux-vt100|linux console with VT100 line-graphics,
U8#0, use=linux,
# uxterm with vt100Graphics resource set to false
xterm-utf8|xterm relying on UTF-8 line-graphics,
U8#1, use=xterm,
The two-character name “U8” was chosen to permit its use via ncurses's termcap interface.
NCURSES_TRACE
At initialization, ncurses (in its debugging configuration) checks for this variable's presence. If
defined with an integral value, the library calls curses_trace(3NCURSES) with that value as the argument.
TERM
The TERM variable denotes the terminal type. Each is distinct, though many are similar. It is commonly
set by terminal emulators to help applications find a workable terminal description. Some choose a
popular approximation such as “ansi”, “vt100”, or “xterm” rather than an exact fit to their capabilities.
Not infrequently, an application will have problems with that approach; for example, a key stroke may not
operate correctly, or produce no effect but seeming garbage characters on the screen.
Setting TERM has no effect on hardware operation; it affects the way applications communicate with the
terminal. Likewise, as a general rule (xterm(1) being a rare exception), terminal emulators that allow
you to specify TERM as a parameter or configuration value do not change their behavior to match that
setting.
TERMCAP
If ncurses is configured with termcap support, it checks for a terminal type description in termcap
format if one in terminfo format is not available. Setting this variable directs ncurses to ignore the
usual termcap database location, /etc/termcap; see TERMPATH below. TERMCAP should contain either a
terminal description (with newlines stripped out), or a file name indicating where the information
required by the TERM environment variable is stored.
TERMINFO
ncurses can be configured to read terminal type description databases in various locations using
different formats. This variable overrides the default location.
• Descriptions in terminfo format are normally stored in a directory tree using subdirectories named
for the common first letters of the terminal types named therein. System V used this scheme.
• If ncurses is configured to use hashed databases, then TERMINFO may name its location, such as
/usr/share/terminfo.db, rather than /usr/share/terminfo/.
The hashed database uses less disk space and is a little faster than the directory tree. However, some
applications assume the existence of the directory tree and read it directly, ignoring the terminfo API.
• If ncurses is configured with termcap support, this variable may contain the location of a termcap
file.
• If the value of TERMINFO begins with “hex:” or “b64:”, ncurses uses the remainder of the value as a
compiled terminfo description. You might produce the base64 format using infocmp(1).
TERMINFO=$(infocmp -0 -Q2 -q)
export TERMINFO
ncurses uses the compiled description only if it corresponds to the terminal type identified by TERM.
Setting TERMINFO is the simplest, but not the only, way to direct ncurses to a terminal database. The
search path is as follows.
• the last terminal database to which the running ncurses application wrote, if any
• the location specified by the TERMINFO environment variable
• $HOME/.terminfo
• locations listed in the TERMINFO_DIRS environment variable
• location(s) configured and compiled into ncurses
• /etc/terminfo:/lib/terminfo:/usr/share/terminfo
• /etc/terminfo
TERMINFO_DIRS
This variable specifies a list of locations, akin to PATH, in which ncurses searches for the terminal
type descriptions described by TERMINFO above. The list items are separated by colons on Unix and
semicolons on OS/2 EMX. System V terminfo lacks a corresponding feature; TERMINFO_DIRS is an ncurses
extension.
TERMPATH
If TERMCAP does not hold a terminal type description or file name, then ncurses checks the contents of
TERMPATH, a list of locations, akin to PATH, in which it searches for termcap terminal type descriptions.
The list items are separated by colons on Unix and semicolons on OS/2 EMX.
If both TERMCAP and TERMPATH are unset or invalid, ncurses searches for the files /etc/termcap,
/usr/share/misc/termcap, and $HOME/.termcap, in that order.
ALTERNATE CONFIGURATIONS
Many different ncurses configurations are possible, determined by the options given to the configure
script when building the library. Run the script with the --help option to peruse them all. A few are
of particular significance to the application developer employing ncurses.
--disable-overwrite
Avoid file name conflicts between ncurses and an existing curses installation on the system. The
standard C preprocessor inclusion for the curses library is as follows.
#include <curses.h>
If ncurses is installed disabling overwrite, it puts its header files in a subdirectory. Here is an
example.
#include <ncurses/curses.h>
With --disable-overwrite, installation also omits a symbolic link that would cause the compiler's
-lcurses option to link object files with ncurses instead of the system curses library.
The directory used by this configuration of ncurses is shown in section “SYNOPSIS” above.
--enable-widec
(default for ABI 6+ since 2023-10-21) Enable support for wide characters. The configure script
renames the ncurses library (and the tinfo library, if --with-termlib is also specified), appending
“w”. An application desirous of wide-character support then uses -lncursesw (or -ltinfow) instead
of -lncurses (or -ltinfo) as its linker option. The ncurses++, panel, form, and menu libraries are
renamed similarly.
An application must also define certain C preprocessor symbols to enable wide-character features in
curses header files to use the extended (wide-character) functions. The symbol that enables these
features has changed since X/Open Curses Issue 4.
• Originally, the wide-character feature required the symbol _XOPEN_SOURCE_EXTENDED, but that was
valid only for XPG4 (1996).
• Later, that was deemed conflicting with an _XOPEN_SOURCE value of 500.
• As of mid-2018, no ncurses feature requires a _XOPEN_SOURCE value greater than 600. However,
X/Open Curses Issue 7 (2009) recommends defining it to 700.
• Alternatively, you can enable the feature by defining NCURSES_WIDECHAR with the caveat that some
header file other than curses.h may require a specific value for _XOPEN_SOURCE (or a system-
specific symbol).
The curses.h header file installed for the wide-character library is designed to be compatible with
the non-wide library's header. Only the size of the WINDOW structure differs; few applications
require more than pointers to WINDOW.
If ncurses's header files are installed allowing overwrite (the default, but see --disable-overwrite
above), the wide-character library's headers should be installed last by packaging systems and
similar, to allow applications to be built using either library from the same set of headers.
--with-pthread
Enable support for multi-threaded applications. The configure script renames the ncurses library
(and the tinfo library, if --with-termlib is also specified), appending “t” (before any “w” added by
--enable-widec). An application desirous of support for multiple threads of execution then uses,
for example, -lncursest (or -ltinfot) instead of -lncurses (or -ltinfo) as its linker option. The
ncurses++, panel, form, and menu libraries are renamed similarly.
ncursest and ncursestw replace global variables such as LINES with macros allowing read-only access.
At the same time, they provide functions to set these values. Very few applications require changes
to work with this convention.
--with-shared
--with-normal
--with-debug
--with-profile
Mandate compilation of the ncurses library (and the tinfo library, if --with-termlib is also
specified) in the specified forms. The shared and normal (static) library names differ by their
suffixes, as with libncurses.so and libncurses.a. The debugging and profiling libraries add a “_g”
and a “_p” to the roots of these respective names, forming libncurses_g.so and libncurses_p.a, for
example. The ncurses++, panel, form, and menu libraries are made available similarly.
--with-termlib
Provide ncurses's lower-level terminal interface functions (those that do not depend on the SCREEN
and WINDOW abstractions) in a library named tinfo. This arrangement reduces an application's
linking and/or loading times when it does not require curses's higher-level features.
The following pages document curses functions provided by tinfo.
• extensions(3NCURSES) - miscellaneous ncurses extensions
• inopts(3NCURSES) - curses input options
• kernel(3NCURSES) - low-level curses routines
• termattrs(3NCURSES) - curses environment query routines
• termcap(3NCURSES) - curses emulation of termcap
• terminfo(3NCURSES) - curses interface to terminfo database
• util(3NCURSES) - miscellaneous curses utility routines
--with-trace
Expose the curses_trace(3NCURSES) function in the ncurses(w) shared and static libraries. Normally,
it is available only in the debugging library. (If --with-termlib is also specified, tinfo(w)
rather than ncurses(w) supplies the deprecated trace(3NCURSES) function.) An application's
configuration script should check for the function's existence rather than assuming its confinement
to the debugging library.
FILES
/usr/share/tabset
tab stop initialization database
/etc/terminfo
compiled terminal capability database
NOTES
X/Open Curses permits most functions it specifies to be made available as macros as well. ncurses does
so
• for functions that return values via their parameters,
• to support obsolete features,
• to reuse functions (for example, those that move the cursor before another operation), and
• in a few special cases.
If the standard output file descriptor of an ncurses program is redirected to something that is not a
terminal device, the library writes screen updates to the standard error file descriptor. This was an
undocumented feature of SVr3 curses.
See subsection “Header Files” below regarding symbols exposed by inclusion of curses.h.
EXTENSIONS
ncurses enables an application to capture mouse events from certain terminals, including xterm(1); see
mouse(3NCURSES).
ncurses provides a means of responding to window resizing events, as when running in a GUI terminal
emulator application such as xterm; see resizeterm(3NCURSES) and wresize(3NCURSES).
ncurses allows an application to query the terminal for the presence of a wide variety of special keys;
see has_key(3NCURSES).
ncurses extends the fixed set of function key capabilities specified by X/Open Curses by allowing the
application programmer to define additional key events at runtime; see define_key(3NCURSES),
key_defined(3NCURSES), keybound(3NCURSES), and keyok(3NCURSES).
ncurses can exploit the capabilities of terminals implementing ISO 6429/ECMA-48 SGR 39 and SGR 49
sequences, which allow an application to reset the terminal to its original foreground and background
colors. From a user's perspective, the application is able to draw colored text on a background whose
color is set independently, providing better control over color contrasts. See default_colors(3NCURSES).
An ncurses application can eschew knowledge of SCREEN and WINDOW structure internals, instead using
accessor functions such as is_cbreak(3NCURSES) and is_scrollok(3NCURSES).
ncurses enables an application to direct its output to a printer attached to the terminal device; see
print(3NCURSES).
ncurses offers slk_attr(3NCURSES) as a counterpart of attr_get(3NCURSES) for soft-label key lines, and
extended_slk_color(3NCURSES) as a form of slk_color(3NCURSES) that can gather color information from them
when many colors are supported.
ncurses permits modification of unctrl(3NCURSES)'s behavior; see use_legacy_coding(3NCURSES).
Rudimentary support for multi-threaded applications may be available; see threads(3NCURSES).
Functions that ease the management of multiple screens can be exposed; see sp_funcs(3NCURSES).
To aid applications to debug their memory usage, ncurses optionally offers functions to more aggressively
free memory it dynamically allocates itself; see memleaks(3NCURSES).
The library facilitates auditing and troubleshooting of its behavior; see trace(3NCURSES).
Compiling ncurses with the option -DUSE_GETCAP causes it to fall back to reading /etc/termcap if the
terminal setup code cannot find a terminfo entry corresponding to TERM. Use of this feature is not
recommended, as it essentially includes an entire termcap compiler in the ncurses startup code, at a cost
in memory usage and application launch latency.
PDCurses and NetBSD curses incorporate some ncurses extensions. Individual man pages indicate where this
is the case.
PORTABILITY
X/Open Curses defines two levels of conformance, “base” and “enhanced”. The latter includes several
additional features, such as wide-character and color support. ncurses intends base-level conformance
with X/Open Curses, and supports all features of its enhanced level except the untic utility.
Differences between X/Open Curses and ncurses are documented in the “PORTABILITY” sections of applicable
man pages.
Error Checking
In many cases, X/Open Curses is vague about error conditions, omitting some of the SVr4 documentation.
Unlike other implementations, ncurses checks pointer parameters, such as those to WINDOW structures, to
ensure that they are not null. This is done primarily to guard against programmer error. The standard
interface does not provide a way for the library to tell an application which of several possible errors
occurred. An application that relies on ncurses to check its function parameters for validity limits its
portability and robustness.
Padding Differences
In historical curses implementations, delays embedded in the terminfo capabilities carriage_return (cr),
scroll_forward (ind), cursor_left (cub1), form_feed (ff), and tab (ht) activated corresponding delay bits
in the Unix terminal driver. ncurses performs all padding by sending NUL bytes to the device. This
method is slightly more expensive, but narrows the interface to the Unix kernel significantly and
correspondingly increases the package's portability.
Header Files
The header file curses.h itself includes the header files stdio.h and unctrl.h.
X/Open Curses has more to say,
The inclusion of curses.h may make visible all symbols from the headers stdio.h, term.h, termios.h,
and wchar.h.
but does not finish the story. A more complete account follows.
• The first curses, in 4BSD, provided a curses.h file.
BSD curses code included curses.h and unctrl.h from an internal header file curses.ext, where “ext”
abbreviated “externs”.
The implementations of printw and scanw used undocumented internal functions of the standard I/O
library (_doprnt and _doscan), but nothing in curses.h itself relied upon stdio.h.
• SVr2 curses added newterm, which relies upon stdio.h because its function prototype employs the FILE
type.
SVr4 curses added putwin and getwin, which also use stdio.h.
X/Open Curses specifies all three of these functions.
SVr4 curses and X/Open Curses do not require the developer to include stdio.h before curses.h. Both
document use of curses as requiring only curses.h.
As a result, standard curses.h always includes stdio.h.
• X/Open Curses and SVr4 curses are inconsistent with respect to unctrl.h.
As noted in util(3NCURSES), ncurses includes unctrl.h from curses.h (as SVr4 does).
• X/Open Curses's comments about term.h and termios.h may refer to HP-UX and AIX.
HP-UX curses includes term.h from curses.h to declare setupterm in curses.h, but ncurses and Solaris
curses do not.
AIX curses includes term.h and termios.h. Again, ncurses and Solaris curses do not.
• X/Open Curses says that curses.h may include term.h, but does not require it to do so.
Some programs use functions declared in both curses.h and term.h, and must include both header files
in the same translation unit.
The header files supplied by ncurses include the standard library headers required for its
declarations, so ncurses's own header files can be included in any order. For portability even to
old AIX systems, include curses.h before term.h.
• X/Open Curses says “may make visible” because including a header file does not necessarily make
visible all of the symbols in it (consider #ifdef and similar).
For instance, ncurses's curses.h may include wchar.h if the proper symbol is defined, and if ncurses
is configured for wide-character support. If wchar.h is included, its symbols may be made visible
depending on the value of the _XOPEN_SOURCE feature test macro.
• X/Open Curses mandates an application's inclusion of one standard C library header in a special case:
stdarg.h before curses.h to prototype the functions vw_printw and vw_scanw (as well as the obsolete
vwprintw and vwscanw). Each of these takes a variadic argument list, a va_list parameter, like that
of printf(3).
SVr3 curses introduced the two obsolete functions, and X/Open Curses the others. In between, SVr4
curses provided for the possibility that an application might include either varargs.h or stdarg.h.
These represented contrasting approaches to handling variadic argument lists. The older interface,
varargs.h, used a pointer to char for variadic functions' va_list parameter. Later, the list
acquired its own standard data type, va_list, defined in stdarg.h, empowering the compiler to check
the types of a function call's actual parameters against the formal ones declared in its prototype.
No conforming implementations of X/Open Curses require an application to include stdarg.h before
curses.h because they either have allowed for a special type, or, like ncurses, they include stdarg.h
themselves to provide a portable interface.
AUTHORS
Zeyd M. Ben-Halim, Eric S. Raymond, Thomas E. Dickey. Based on pcurses by Pavel Curtis.
SEE ALSO
curses_variables(3NCURSES), terminfo(5), user_caps(5)
ncurses 6.5 2025-11-11 ncurses(3NCURSES)