The ncurses routines emulate the curses(3X) library of System V Release 4 UNIX, and the XPG4 curses standard (XSI curses) but the ncurses library is freely redistributable in source form. Differences from the SVr4 curses are summarized under the EXTENSIONS and BUGS sections below and described in detail in the EXTENSIONS and BUGS sections of individual man pages.
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.
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.
To initialize the routines, the routine initscr or newterm must be called 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:
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 which 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 effect 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
(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 /usr/share/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 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. The variables ch and attrs below are always of type chtype. The types WINDOW, SCREEN, bool, and chtype are defined in <curses.h>. The type TERMINAL is defined in <term.h>. All other arguments are integers.
|curses Routine Name||Manual Page Name|
All macros return the value of the w version, except setscrreg, wsetscrreg, getyx, getbegyx, 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.
It is important that your application use a correct size for the screen. However, 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.
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 this feature.
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.
1 = left
2 = right
3 = middle.
This symbol lets you customize the mouse. The symbol must be three numeric digits 1-3 in any order, e.g., 123 or 321. If it is not specified, ncurses uses 132.
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 symbol to disable all but mandatory padding. Mandatory padding is used as a part of special control sequences such as flash.
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.
The TERMCAP symbol contains either a terminal description (with newlines stripped out), or a file name telling where the information denoted by the TERM symbol exists. In either case, setting it directs ncurses to ignore the usual place for this information, e.g., /etc/termcap.
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) 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 use_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.
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 details.
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.
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 NUL sends. This method is slightly more expensive, but narrows the interface to the UNIX kernel significantly and increases the package's portability correspondingly.
In the XSI standard and SVr4 manual pages, many entry points have prototype arguments of the for char *const (or cchar_t *const, or wchar_t *const, or void *const). Depending on one's interpretation of the ANSI C standard (see section 220.127.116.11), these declarations are either (a) meaningless, or (b) meaningless and illegal. The declaration const char *x is a modifiable pointer to unmodifiable data, but char *const x' is an unmodifiable pointer to modifiable data. Given that C passes arguments by value, <type> *const as a formal type is at best dubious. Some compilers choke on the prototypes. Therefore, in this implementation, they have been changed to const <type> * globally.
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.