The ncurses library routines give the user a terminal-independent
method of updating character screens with reasonable optimization.
This implementation is “new curses” (ncurses) and is the approved
replacement for 4.4BSD classic curses, which has been discontinued.
This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch
The ncurses library emulates the curses library of System V Release 4
UNIX, and XPG4 (X/Open Portability Guide) curses (also known as XSI
curses). XSI stands for X/Open System Interfaces Extension. The
ncurses library is freely redistributable in source form.
Differences from the SVr4 curses are summarized under the EXTENSIONS
and PORTABILITY sections below and described in detail in the
respective EXTENSIONS, PORTABILITY and BUGS sections of individual
The ncurses library also provides many useful extensions, i.e.,
features which cannot be implemented by a simple add-on library but
which require access to the internals of the library.
A program using these routines must be linked with the -lncurses
option, or (if it has been generated) with the debugging library
-lncurses_g. (Your system integrator may also have installed these
libraries under the names -lcurses and -lcurses_g.) The ncurses_g
library generates trace logs (in a file called 'trace' in the current
directory) that describe curses actions. See also the section on
The ncurses package supports: overall screen, window and pad
manipulation; output to windows and pads; reading terminal input;
control over terminal and curses input and output options;
environment query routines; color manipulation; use of soft label
keys; terminfo capabilities; and access to low-level terminal-
The library uses the locale which the calling program has
initialized. That is normally done with setlocale:
If the locale is not initialized, the library assumes that characters
are printable as in ISO-8859-1, to work with certain legacy programs.
You should initialize the locale and not rely on specific details of
the library when the locale has not been setup.
The function initscr or newterm must be called to initialize the
library before any of the other routines that deal with windows and
screens are used. The routine endwin(3X) must be called before
To get character-at-a-time input without echoing (most interactive,
screen oriented programs want this), the following sequence should be
initscr(); cbreak(); noecho();
Most programs would additionally use the sequence:
nonl();intrflush(stdscr, FALSE);keypad(stdscr, TRUE);
Before a curses program is run, the tab stops of the terminal should be
set and its initialization strings, if defined, must be output. This can
be done by executing the @TPUT@ init command after the shell environment
variable TERM has been exported. @TSET@(1) is usually responsible for
doing this. [See terminfo(5) for further details.]
The ncurses library permits manipulation of data structures, called
windows, which can be thought of as two-dimensional arrays of
characters representing all or part of a CRT screen. A default
window called stdscr, which is the size of the terminal screen, is
supplied. Others may be created with newwin.
Note that curses does not handle overlapping windows, that's done by
the panel(3X) library. This means that you can either use stdscr or
divide the screen into tiled windows and not using stdscr at all.
Mixing the two will result in unpredictable, and undesired, effects.
Windows are referred to by variables declared as WINDOW *. These
data structures are manipulated with routines described here and
elsewhere in the ncurses manual pages. Among those, the most basic
routines are move and addch. More general versions of these routines
are included with names beginning with w, allowing the user to
specify a window. The routines not beginning with w affect stdscr.
After using routines to manipulate a window, refresh(3X) is called,
telling curses to make the user's CRT screen look like stdscr. The
characters in a window are actually of type chtype, (character and
attribute data) so that other information about the character may
also be stored with each character.
Special windows called pads may also be manipulated. These are
windows which are not constrained to the size of the screen and whose
contents need not be completely displayed. See curs_pad(3X) for more
In addition to drawing characters on the screen, video attributes and
colors may be supported, causing the characters to show up in such
modes as underlined, in reverse video, or in color on terminals that
support such display enhancements. Line drawing characters may be
specified to be output. On input, curses is also able to translate
arrow and function keys that transmit escape sequences into single
values. The video attributes, line drawing characters, and input
values use names, defined in <curses.h>, such as A_REVERSE,
ACS_HLINE, and KEY_LEFT.
If the environment variables LINES and COLUMNS are set, or if the
program is executing in a window environment, line and column
information in the environment will override information read by
terminfo. This would affect a program running in an AT&T 630 layer,
for example, where the size of a screen is changeable (see
If the environment variable TERMINFO is defined, any program using
curses checks for a local terminal definition before checking in the
standard place. For example, if TERM is set to att4424, then the
compiled terminal definition is found in
(The a is copied from the first letter of att4424 to avoid creation of
huge directories.) However, if TERMINFO is set to $HOME/myterms,
curses first checks
and if that fails, it then checks
This is useful for developing experimental definitions or when write
permission in @TERMINFO@ is not available.
The integer variables LINES and COLS are defined in <curses.h> and
will be filled in by initscr with the size of the screen. The
constants TRUE and FALSE have the values 1 and 0, respectively.
The curses routines also define the WINDOW * variable curscr which is
used for certain low-level operations like clearing and redrawing a
screen containing garbage. The curscr can be used in only a few
Routine and Argument Names
Many curses routines have two or more versions. The routines
prefixed with w require a window argument. The routines prefixed
with p require a pad argument. Those without a prefix generally use
The routines prefixed with mv require a y and x coordinate to move to
before performing the appropriate action. The mv routines imply a
call to move before the call to the other routine. The coordinate y
always refers to the row (of the window), and x always refers to the
column. The upper left-hand corner is always (0,0), not (1,1).
The routines prefixed with mvw take both a window argument and x and
y coordinates. The window argument is always specified before the
In each case, win is the window affected, and pad is the pad
affected; win and pad are always pointers to type WINDOW.
Option setting routines require a Boolean flag bf with the value TRUE
or FALSE; bf is always of type bool. Most of the data types used in
the library routines, such as WINDOW, SCREEN, bool, and chtype are
defined in <curses.h>. Types used for the terminfo routines such as
TERMINAL are defined in <term.h>.
This manual page describes functions which may appear in any
configuration of the library. There are two common configurations of
the "normal" library, which handles 8-bit characters. The
normal (8-bit) library stores characters combined with
attributes in chtype data.
Attributes alone (no corresponding character) may be stored
in chtype or the equivalent attr_t data. In either case, the
data is stored in something like an integer.
Each cell (row and column) in a WINDOW is stored as a chtype.
the so-called "wide" library, which handles multibyte
characters (see the section on ALTERNATE CONFIGURATIONS).
The "wide" library includes all of the calls from the
"normal" library. It adds about one third more calls using
data types which store multibyte characters:
corresponds to chtype. However it is a structure,
because more data is stored than can fit into an
integer. The characters are large enough to require a
full integer value - and there may be more than one
character per cell. The video attributes and color are
stored in separate fields of the structure.
Each cell (row and column) in a WINDOW is stored as a
stores a "wide" character. Like chtype, this may be an
stores a wchar_t or WEOF - not the same, though both may
have the same size.
The "wide" library provides new functions which are analogous
to functions in the "normal" library. There is a naming
convention which relates many of the normal/wide variants: a
"_w" is inserted into the name. For example, waddch becomes
Routine Name Index
The following table lists each curses routine and the name of the
manual page on which it is described. Routines flagged with “*” are
ncurses-specific, not described by XPG4 or present in SVr4.
curses Routine Name Manual Page Name
Routines that return an integer return ERR upon failure and an
integer value other than ERR upon successful completion, unless
otherwise noted in the routine descriptions.
As a general rule, routines check for null pointers passed as
parameters, and handle this as an error.
All macros return the value of the w version, except setscrreg,
wsetscrreg, getyx, getbegyx, and getmaxyx. The return values of
setscrreg, wsetscrreg, getyx, getbegyx, and getmaxyx are undefined
(i.e., these should not be used as the right-hand side of assignment
Routines that return pointers return NULL on error.
The following environment symbols are useful for customizing the
runtime behavior of the ncurses library. The most important ones
have been already discussed in detail.
When set, change occurrences of the command_character (i.e., the
cmdch capability) of the loaded terminfo entries to the value of this
variable. Very few terminfo entries provide this feature.
Because this name is also used in development environments to
represent the C compiler's name, ncurses ignores it if it does not
happen to be a single character.
The debugging library checks this environment variable when the
application has redirected output to a file. The variable's numeric
value is used for the baudrate. If no value is found, ncurses uses
9600. This allows testers to construct repeatable test-cases that
take into account costs that depend on baudrate.
Specify the width of the screen in characters. Applications running
in a windowing environment usually are able to obtain the width of
the window in which they are executing. If neither the COLUMNS value
nor the terminal's screen size is available, ncurses uses the size
which may be specified in the terminfo database (i.e., the cols
It is important that your application use a correct size for the
screen. This is not always possible because your application may be
running on a host which does not honor NAWS (Negotiations About
Window Size), or because you are temporarily running as another user.
However, setting COLUMNS and/or LINES overrides the library's use of
the screen size obtained from the operating system.
Either COLUMNS or LINES symbols may be specified independently. This
is mainly useful to circumvent legacy misfeatures of terminal
descriptions, e.g., xterm which commonly specifies a 65 line screen.
For best results, lines and cols should not be specified in a
terminal description for terminals which are run as emulations.
Use the use_env function to disable all use of external environment
(but not including system calls) to determine the screen size. Use
the use_tioctl function to update COLUMNS or LINES to match the
screen size obtained from system calls or the terminal database.
Specifies the total time, in milliseconds, for which ncurses will
await a character sequence, e.g., a function key. The default value,
1000 milliseconds, is enough for most uses. However, it is made a
variable to accommodate unusual applications.
The most common instance where you may wish to change this value is
to work with slow hosts, e.g., running on a network. If the host
cannot read characters rapidly enough, it will have the same effect
as if the terminal did not send characters rapidly enough. The
library will still see a timeout.
Note that xterm mouse events are built up from character sequences
received from the xterm. If your application makes heavy use of
multiple-clicking, you may wish to lengthen this default value
because the timeout applies to the composed multi-click event as well
as the individual clicks.
In addition to the environment variable, this implementation provides
a global variable with the same name. 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.
Tells ncurses where your home directory is. That is where it may
read and write auxiliary terminal descriptions:
Like COLUMNS, specify the height of the screen in characters. See
COLUMNS for a detailed description.
This applies only to the OS/2 EMX port. It specifies the order of
buttons on the mouse. OS/2 numbers a 3-button mouse inconsistently
from other platforms:
1 = left
2 = right
3 = middle.
This variable lets you customize the mouse. The variable must be
three numeric digits 1-3 in any order, e.g., 123 or 321. If it is
not specified, ncurses uses 132.
Override the compiled-in assumption that the terminal's default
colors are white-on-black (see default_colors(3X)). You may set the
foreground and background color values with this environment variable
by proving a 2-element list: foreground,background. For example, to
tell ncurses to not assume anything about the colors, set this to
"-1,-1". To make it green-on-black, set it to "2,0". Any positive
value from zero to the terminfo max_colors value is allowed.
This applies only to the MinGW port of ncurses.
The Console2 program's handling of the Microsoft Console API call
CreateConsoleScreenBuffer is defective. Applications which use this
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.
This applies only to ncurses configured to use the GPM interface.
If present, the environment variable is a list of one or more
terminal names against which the TERM environment variable is
matched. Setting it to an empty value disables the GPM interface;
using the built-in support for xterm, etc.
If the environment variable is absent, ncurses will attempt to open
GPM if TERM contains "linux".
NCURSES_NO_HARD_TABSNcurses may use tabs as part of the cursor movement optimization. In
some cases, your terminal driver may not handle these properly. Set
this environment variable to disable the feature. You can also
adjust your stty settings to avoid the problem.
NCURSES_NO_MAGIC_COOKIE Some terminals use a magic-cookie feature
which requires special handling to make highlighting and other video
attributes display properly. You can suppress the highlighting
entirely for these terminals by setting this environment variable.
Most of the terminal descriptions in the terminfo database are
written for real "hardware" terminals. Many people use terminal
emulators which run in a windowing environment and use curses-based
applications. Terminal emulators can duplicate all of the important
aspects of a hardware terminal, but they do not have the same
limitations. The chief limitation of a hardware terminal from the
standpoint of your application is the management of dataflow, i.e.,
timing. Unless a hardware terminal is interfaced into a terminal
concentrator (which does flow control), it (or your application) must
manage dataflow, preventing overruns. The cheapest solution (no
hardware cost) is for your program to do this by pausing after
operations that the terminal does slowly, such as clearing the
As a result, many terminal descriptions (including the vt100) have
delay times embedded. You may wish to use these descriptions, but
not want to pay the performance penalty.
Set the NCURSES_NO_PADDING environment variable to disable all but
mandatory padding. Mandatory padding is used as a part of special
control sequences such as flash.
This setting is obsolete. Before changes
· started with 5.9 patch 20120825 and
· continued though 5.9 patch 20130126
ncurses enabled buffered output during terminal initialization. This
was done (as in SVr4 curses) for performance reasons. For testing
purposes, both of ncurses and certain applications, this feature was
made optional. Setting the NCURSES_NO_SETBUF variable disabled
output buffering, leaving the output in the original (usually line
In the current implementation, ncurses performs its own buffering and
does not require this workaround. It does not modify the buffering
of the standard output.
The reason for the change was to make the behavior for interrupts and
other signals more robust. One drawback is that certain
nonconventional programs would mix ordinary stdio calls with ncurses
calls and (usually) work. This is no longer possible since ncurses
is not using the buffered standard output but its own output (to the
same file descriptor). As a special case, the low-level calls such
as putp still use the standard output. But high-level curses calls
During initialization, the ncurses library checks for special cases
where VT100 line-drawing (and the corresponding alternate character
set capabilities) described in the terminfo are known to be missing.
Specifically, when running in a UTF-8 locale, the Linux console
emulator and the GNU screen program ignore these. Ncurses checks the
TERM environment variable for these. For other special cases, you
should set this environment variable. Doing this tells ncurses to
use Unicode values which correspond to the VT100 line-drawing glyphs.
That works for the special cases cited, and is likely to work for
When setting this variable, you should set it to a nonzero value.
Setting it to zero (or to a nonnumber) disables the special check for
"linux" and "screen".
As an alternative to the environment variable, ncurses checks for an
extended terminfo capability U8. This is a numeric capability which
can be compiled using @TIC@ -x. For example
# linux console, if patched to provide working
# VT100 shift-in/shift-out, with corresponding font.
linux-vt100|linux console with VT100 line-graphics,
# uxterm with vt100Graphics resource set to false
xterm-utf8|xterm relying on UTF-8 line-graphics,
The name "U8" is chosen to be two characters, to permit it to be used
by applications that use ncurses' termcap interface.
During initialization, the ncurses debugging library checks the
NCURSES_TRACE environment variable. If it is defined, to a numeric
value, ncurses calls the trace function, using that value as the
The argument values, which are defined in curses.h, provide several
types of information. When running with traces enabled, your
application will write the file trace to the current directory.
See curs_trace(3X) for more information.
Denotes your terminal type. Each terminal type is distinct, though
many are similar.
TERM is commonly set by terminal emulators to help applications find
a workable terminal description. Some of those choose a popular
approximation, e.g., “ansi”, “vt100”, “xterm” rather than an exact
fit. Not infrequently, your application will have problems with that
approach, e.g., incorrect function-key definitions.
If you set TERM in your environment, it has no effect on the
operation of the terminal emulator. It only affects the way
applications work within the terminal. Likewise, as a general rule
(xterm being a rare exception), terminal emulators which allow you to
specify TERM as a parameter or configuration value do not change
their behavior to match that setting.
If the ncurses library has been configured with termcap support,
ncurses will check for a terminal's description in termcap form if it
is not available in the terminfo database.
The TERMCAP environment variable contains either a terminal
description (with newlines stripped out), or a file name telling
where the information denoted by the TERM environment variable
exists. In either case, setting it directs ncurses to ignore the
usual place for this information, e.g., /etc/termcap.
TERMINFOncurses can be configured to read from multiple terminal databases.
The TERMINFO variable overrides the location for the default terminal
database. Terminal descriptions (in terminal format) are stored in
· Normally these are stored in a directory tree, using
subdirectories named by the first letter of the terminal names
This is the scheme used in System V, which legacy Unix systems
use, and the TERMINFO variable is used by curses applications on
those systems to override the default location of the terminal
· If ncurses is built to use hashed databases, then each entry in
this list may be the path of a hashed database file, e.g.,
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, reading it directly rather than
using the terminfo library calls.
· If ncurses is built with a support for reading termcap files
directly, then an entry in this list may be the path of a termcap
· If the TERMINFO variable begins with “hex:” or “b64:”, ncurses
uses the remainder of that variable as a compiled terminal
description. You might produce the base64 format using
TERMINFO="$(infocmp -0 -Q2 -q)"
The compiled description is used if it corresponds to the
terminal identified by the TERM variable.
Setting TERMINFO is the simplest, but not the only way to set
location of the default terminal database. The complete list of
database locations in order follows:
· the last terminal database to which ncurses wrote, if any, is
· the location specified by the TERMINFO environment variable
· locations listed in the TERMINFO_DIRS environment variable
· one or more locations whose names are configured and compiled
into the ncurses library, i.e.,
· @TERMINFO_DIRS@ (corresponding to the TERMINFO_DIRS
· @TERMINFO@ (corresponding to the TERMINFO variable)
Specifies a list of locations to search for terminal descriptions.
Each location in the list is a terminal database as described in the
section on the TERMINFO variable. The list is separated by colons
(i.e., ":") on Unix, semicolons on OS/2 EMX.
There is no corresponding feature in System V terminfo; it is an
extension developed for ncurses.
If TERMCAP does not hold a file name then ncurses checks the TERMPATH
environment variable. This is a list of filenames separated by
spaces or colons (i.e., ":") on Unix, semicolons on OS/2 EMX.
If the TERMPATH environment variable is not set, ncurses looks in the
/etc/termcap, /usr/share/misc/termcap and $HOME/.termcap,
in that order.
The library may be configured to disregard the following variables
when the current user is the superuser (root), or if the application
uses setuid or setgid permissions:
$TERMINFO, $TERMINFO_DIRS, $TERMPATH, as well as $HOME.
Several different configurations are possible, depending on the
configure script options used when building ncurses. There are a few
main options whose effects are visible to the applications developer
The standard include for ncurses is as noted in SYNOPSIS:
This option is used to avoid filename conflicts when ncurses is
not the main implementation of curses of the computer. If
ncurses is installed disabling overwrite, it puts its headers in
a subdirectory, e.g.,
It also omits a symbolic link which would allow you to use
-lcurses to build executables.
The configure script renames the library and (if the
--disable-overwrite option is used) puts the header files in a
different subdirectory. All of the library names have a "w"
appended to them, i.e., instead of
you link with
You must also define _XOPEN_SOURCE_EXTENDED when compiling for
the wide-character library to use the extended (wide-character)
functions. The curses.h file which is installed for the wide-
character library is designed to be compatible with the normal
library's header. Only the size of the WINDOW structure
differs, and very few applications require more than a pointer
to WINDOWs. If the headers are installed allowing overwrite,
the wide-character library's headers should be installed last,
to allow applications to be built using either library from the
same set of headers.
The configure script renames the library. All of the library
names have a "t" appended to them (before any "w" added by
The global variables such as LINES are replaced by macros to
allow read-only access. At the same time, setter-functions are
provided to set these values. Some applications (very few) may
require changes to work with this convention.
The shared and normal (static) library names differ by their
suffixes, e.g., libncurses.so and libncurses.a. The debug and
profiling libraries add a "_g" and a "_p" to the root names
respectively, e.g., libncurses_g.a and libncurses_p.a.
The trace function normally resides in the debug library, but it
is sometimes useful to configure this in the shared library.
Configure scripts should check for the function's existence
rather than assuming it is always in the debug library.
The ncurses library can be compiled with an option (-DUSE_GETCAP)
that falls back to the old-style /etc/termcap file 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 significant
cost in core and startup cycles.
The ncurses library includes facilities for capturing mouse events on
certain terminals (including xterm). See the curs_mouse(3X) manual
page for details.
The ncurses library includes facilities for responding to window
resizing events, e.g., when running in an xterm. See the
resizeterm(3X) and wresize(3X) manual pages for details. In
addition, the library may be configured with a SIGWINCH handler.
The ncurses library extends the fixed set of function key
capabilities of terminals by allowing the application designer to
define additional key sequences at runtime. See the define_key(3X)
key_defined(3X), and keyok(3X) manual pages for details.
The ncurses library can exploit the capabilities of terminals which
implement the ISO-6429 SGR 39 and SGR 49 controls, which allow an
application to reset the terminal to its original foreground and
background colors. From the users' perspective, the application is
able to draw colored text on a background whose color is set
independently, providing better control over color contrasts. See
the default_colors(3X) manual page for details.
The ncurses library includes a function for directing application
output to a printer attached to the terminal device. See the
curs_print(3X) manual page for details.
The ncurses library is intended to be BASE-level conformant with XSI
Curses. The EXTENDED XSI Curses functionality (including color
support) is supported.
A small number of local differences (that is, individual differences
between the XSI Curses and ncurses calls) are described in
PORTABILITY sections of the library man pages.
Unlike other implementations, this one checks parameters such as
pointers to WINDOW structures to ensure they are not null. The main
reason for providing this behavior is 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 were
detected. Relying on this (or some other) extension will adversely
affect the portability of curses applications.
This implementation also contains several extensions:
· The routine has_key is not part of XPG4, nor is it present in
SVr4. See the curs_getch(3X) manual page for details.
· The routine slk_attr is not part of XPG4, nor is it present in
SVr4. See the curs_slk(3X) manual page for details.
· The routines getmouse, mousemask, ungetmouse, mouseinterval, and
wenclose relating to mouse interfacing are not part of XPG4, nor
are they present in SVr4. See the curs_mouse(3X) manual page for
· The routine mcprint was not present in any previous curses
implementation. See the curs_print(3X) manual page for details.
· The routine wresize is not part of XPG4, nor is it present in
SVr4. See the wresize(3X) manual page for details.
· The WINDOW structure's internal details can be hidden from
application programs. See curs_opaque(3X) for the discussion of
· This implementation can be configured to provide rudimentary
support for multi-threaded applications. See curs_threads(3X)
· This implementation can also be configured to provide a set of
functions which improve the ability to manage multiple screens.
See curs_sp_funcs(3X) for details.
In historic curses versions, delays embedded in the capabilities cr,
ind, cub1, ff and tab activated corresponding delay bits in the UNIX
tty driver. In this implementation, all padding is done by sending
NUL bytes. This method is slightly more expensive, but narrows the
interface to the UNIX kernel significantly and increases the
package's portability correspondingly.
The header file <curses.h> automatically includes the header files
<stdio.h> and <unctrl.h>.
If standard output from a ncurses program is re-directed to something
which is not a tty, screen updates will be directed to standard
error. This was an undocumented feature of AT&T System V Release 3
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
email@example.com. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2017-03-13. 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