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 man pages.

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 ALTERNATE CONFIGURATIONS.

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-manipulation routines.

The library uses the locale which the calling program has initialized. That is normally done with setlocale: setlocale(LC_ALL, ""); 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 must be called before exiting.

To get character-at-a-time input without echoing (most interactive, screen oriented programs want this), the following sequence should be used: 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(\*n) 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 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 information.

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 ENVIRONMENT).

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 \*d/a/att4424. (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 $HOME/myterms/a/att4424, and if that fails, it then checks \*d/a/att4424. This is useful for developing experimental definitions or when write permission in \*d 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 routines.

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 coordinates.

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 library:

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 statements).

Routines that return pointers return NULL on error.

5 BAUDRATE 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.

5 CC 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.

5 COLUMNS 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 capability).

5 ESCDELAY 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.

5 HOME Tells ncurses where your home directory is. That is where it may read and write auxiliary terminal descriptions:

$HOME/.terminfo

5 LINES Like COLUMNS, specify the height of the screen in characters. See COLUMNS for a detailed description.

5 MOUSE_BUTTONS_123 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.

5 NCURSES_ASSUMED_COLORS 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.

5 NCURSES_GPM_TERMS This applies only to ncurses configured to use the GPM interface.

5 NCURSES_NO_HARD_TABS Ncurses 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.

5 NCURSES_NO_MAGIC_COOKIES 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.

5 NCURSES_NO_PADDING 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 display.

5 NCURSES_NO_SETBUF This setting is obsolete. Before changes

5 NCURSES_NO_UTF8_ACS 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 terminal emulators.

# 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,

5 NCURSES_TRACE 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 argument.

5 TERM Denotes your terminal type. Each terminal type is distinct, though many are similar.

5 TERMCAP 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.

5 TERMINFO Overrides the directory in which ncurses searches for your terminal description. This is the simplest, but not the only way to change the list of directories. The complete list of directories in order follows:

5 TERMINFO_DIRS Specifies a list of directories to search for terminal descriptions. The list is separated by colons (i.e., ":") on Unix, semicolons on OS/2 EMX.

5 TERMPATH 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.

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:

5 --disable-overwrite The standard include for ncurses is as noted in SYNOPSIS:

5 --enable-widec 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

5 --with-shared

--with-normal

--with-debug

--with-profile 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.

5 --with-trace 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.

5 @DATADIR@/tabset directory containing initialization files for the terminal capability database @TERMINFO@ terminal capability database

curs_variables(3X)

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.

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: .bP The routine has_key is not part of XPG4, nor is it present in SVr4. See the curs_getch(3X) manual page for details. .bP The routine slk_attr is not part of XPG4, nor is it present in SVr4. See the curs_slk(3X) manual page for details. .bP 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 details. .bP The routine mcprint was not present in any previous curses implementation. See the curs_print(3X) manual page for details. .bP The routine wresize is not part of XPG4, nor is it present in SVr4. See the wresize(3X) manual page for details. .bP The WINDOW structure's internal details can be hidden from application programs. See curs_opaque(3X) for the discussion of is_scrollok, etc. .bP This implementation can be configured to provide rudimentary support for multi-threaded applications. See curs_threads(3X) for details. .bP 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.

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 curses.