+ The "new curses" library offers the programmer a terminal-independent
+ means of reading keyboard and mouse input and updating character-cell
+ terminals 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 20240427).
+
+ ncurses permits control of the terminal screen's contents; abstraction
+ and subdivision thereof with windows and pads; the reading of terminal
+ input; control of terminal input and output options; environment query
+ routines; color manipulation; the definition and use of softlabel
+ keys; terminfo capability access; a termcap compatibility interface;
+ and an abstraction of the system's API for manipulating the terminal
+ (such as termios(3)).
+
+ ncurses implements the standard 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.
+
+ o "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 that will be significant to the programmer
+ but which are not standardized.
+
+ o "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.
+
+ o "PORTABILITY" discusses matters (beyond the exercise of extensions)
+ that should be considered when writing to a curses standard, or for
+ multiple implementations.
+
+ o "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
+ generates trace logs (in a file called trace in the current directory)
+ that describe ncurses actions. See section "ALTERNATE CONFIGURATIONS"
+ below.
+
+
+
+ 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(3x) or newterm(3x) must be called to initialize curses before
+ use of any functions that deal with windows and 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 perform further setup as follows.
+
+ intrflush(stdscr, FALSE);
+ keypad(stdscr, TRUE);
+
+ A curses program then often enters an event loop of some sort. Call
+ endwin(3x) before exiting.
+
+
+
+ A curses library abstracts the terminal screen by representing all or
+ part of it as a WINDOW data structure. A window is a rectangular grid
+ of character cells, addressed by row and column coordinates (y, x),
+ with the upper left corner as (0, 0). A window called stdscr, the same
+ size as the terminal screen, is always available. Create others with
+ newwin(3x).
+
+ 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 output operation will occur.
+ Among those, the most basic are move(3x) and addch(3x): these place the
+ cursor 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 the
+ library does not generally update it automatically. Therefore, after
+ using curses functions to accumulate a set of desired updates that make
+ sense to present together, call refresh(3x) to tell the library to make
+ the user's screen look like stdscr. The library optimizes its output
+ by computing a minimal number 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(3x)
+ API, a feature of every standard curses implementation.
+
+ Special windows called pads may also be manipulated. These are windows
+ that are not constrained to the size of the terminal screen and whose
+ contents need not be completely displayed. See curs_pad(3x).
+
+ In addition to drawing characters on the screen, rendering 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. See curs_attr(3x).
+
+ curses predefines constants for a small set of forms-drawing graphics
+ corresponding to the DEC Alternate Character Set (ACS), a feature of
+ VT100 and other terminals. See waddch(3x).
+
+ curses is implemented using the operating system's terminal driver;
+ keystroke events are received not as scan codes but as byte sequences.
+ Graphical keycaps (alphanumeric and punctuation keys, and the space)
+ appear as-is. Everything else, including the tab, enter/return,
+ keypad, arrow, and function keys, appears as a control character or a
+ multibyte escapesequence.curses translates these into unique key
+ codes. See getch(3x).
+
+ ncurses provides reimplementations of the SVr4 panel(3x), form(3x), and
+ menu(3x) libraries to ease construction of user interfaces with curses.
+
+
+
+ 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, export the TERM environment variable
+ in the shell, then run tset(1) or the "tputinit" 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 terminals; see wresize(3x).
+
+ 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 experimental type
+ descriptions or when write permission to /usr/share/terminfo is not
+ available.
+
+ See section "ENVIRONMENT" below.
+
+
+
+ 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(3x); 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.
+
+ In function synopses, ncurses man pages apply the following names to
+ parameters.
+
+ bfbool (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
+
+
+
+ This manual page describes functions that appear in any configuration
+ of the library. There are two common configurations; 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 in a chtype datum, which is often an alias of int.
+
+ Attributes alone (with no corresponding character) can be
+ stored in variables of chtype or attr_t type. In either
+ case, they are represented as an integral bit mask.
+
+ Each cell of a WINDOW is stored as a chtype.
+
+ 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 adds about one third more
+ calls using additional data types that can store such
+ multibyte characters.
+
+ cchar_t corresponds to the non-wide configuration's chtype.
+ It always a structure type, because it stores more
+ data than fit into a standard scalar type. 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). Attributes
+ and color data are stored in separate fields of the
+ structure, not combined as in chtype.
+
+ Each cell of a WINDOW is stored as a cchar_t.
+
+ setcchar(3x) and getcchar(3x) 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.
+
+ The wide library 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.
+ (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".
+
+
+
+ Unless otherwise noted, functions that return an integer return OK on
+ success and ERR on failure. Functions that return pointers return NULL
+ 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.
+
+
+
+ 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).
+
+
+
+ The debugging library checks this variable when the application has
+ redirected output to a file. Its integral value is used for the baud
+ rate. If that value is absent or invalid, ncurses uses 9600. This
+ feature allows testers to construct repeatable test cases that take
+ into account optimization decisions that depend on baud rate.
+
+
+
+ When set, the command_character (cmdch) capability value of loaded
+ terminfo entries changes to the value of this variable. Very few term-
+ info entries provide this feature.
+
+ Because this name is also used in development environments to represent
+ the C compiler's name, ncurses ignores its value if it is not one
+ character in length.
+
+
+
+ This variable specifies 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 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(3x) can disable use of the process environment in determining
+ the screen size. use_tioctl(3x) can update COLUMNS and LINES to match
+ the screen size obtained from system calls or the terminal database.
+
+
+
+ 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
+ escapesequence (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.
+
+ 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.
+
+ 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(3x) is disabled for the curses window receiving input, a
+ program must disambiguate escape sequences itself.
+
+
+
+ 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.
+
+
+
+ (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".
+
+
+
+ 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(3x). 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, use "2,0". ncurses accepts integral values from -1 up to the
+ value of the terminfomax_colors (colors) capability.
+
+
+
+ (MinGW port only) The Console2 program defectively handles the
+ Microsoft Console API call CreateConsoleScreenBuffer. 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.
+
+
+
+ (Linux only) When ncurses is configured to use the GPM interface, this
+ variable may list one or more terminal names 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 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.
+
+
+
+ Many terminals store video attributes as a property of a character
+ cell, as curses does. Historically, some recorded changes in video
+ attributes as data that logically occupies character cells on the
+ display, switching attributes on or off, similarly to tags in a markup
+ language; these are termed "magic cookies", and must be subsequently
+ overprinted. 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.
+
+
+
+ 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 control itself to
+ prevent overruns and data loss.
+
+ A solution that comes at no hardware cost is for an application to
+ pause 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).
+
+
+
+ (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 signal handling, as for interrupts, 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(3x) still use the
+ standard output stream. High-level curses calls such as printw(3x) do
+ not.
+
+
+
+ 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.
+
+
+
+ At initialization, ncurses (in its debugging configuration) checks for
+ this variable's presence. If defined with an integral value, the
+ library calls curses_trace(3x) with that value as the argument.
+
+
+
+ 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.
+
+
+
+ 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.
-
-
RETURN VALUE
- Routines that return an integer return ERR upon failure
- and an integer value other than ERR upon successful com-
- pletion, unless otherwise noted in the routine descrip-
- tions.
+
+ ncurses can be configured to read terminal type description databases
+ in various locations using different formats. This variable overrides
+ the default location.
- As a general rule, routines check for null pointers passed
- as parameters, and handle this as an error.
+ o Descriptions in terminfo format are normally stored in a directory
+ tree using subdirectories named by the common first letters of the
+ terminal types named therein. This is the scheme used in System V.
- 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).
+ o 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/.
- Routines that return pointers return NULL on error.
+ 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 rather than using the terminfo
+ API.
+ o If ncurses is configured with termcap support, this variable may
+ contain the location of a termcap file.
-
-
ENVIRONMENT
- The following environment symbols are useful for customiz-
- ing the runtime behavior of the ncurses library. The most
- important ones have been already discussed in detail.
-
- 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 ter-
- minfo entries provide this feature.
-
- Because this name is also used in development envi-
- ronments to represent the C compiler's name, ncurses
- ignores it if it does not happen to be a single char-
- acter.
-
- BAUDRATE
- The debugging library checks this environment vari-
- able 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.
-
- COLUMNS
- Specify the width of the screen in characters.
- Applications running in a windowing environment usu-
- ally 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).
-
- 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 exter-
- nal environment (but not including system calls) to
- determine the screen size. Use the use_tioctl func-
- tion to update COLUMNS or LINES to match the screen
- size obtained from system calls or the terminal data-
- base.
-
- 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 vari-
- able 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 char-
- acter 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 imple-
- mentation 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 applica-
- tion.
-
- HOME Tells ncurses where your home directory is. That is
- where it may read and write auxiliary terminal
- descriptions:
-
- $HOME/.termcap
- $HOME/.terminfo
-
- LINES
- Like COLUMNS, specify the height of the screen in
- characters. See COLUMNS for a detailed description.
-
- 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.
-
- NCURSES_ASSUMED_COLORS
- Override the compiled-in assumption that the termi-
- nal's default colors are white-on-black (see
- default_colors(3x)). You may set the foreground and
- background color values with this environment vari-
- able by proving a 2-element list: foreground,back-
- ground. 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 posi-
- tive value from zero to the terminfo max_colors value
- is allowed.
-
- NCURSES_CONSOLE2
- This applies only to the MinGW port of ncurses.
-
- The Console2 program's handling of the Microsoft Con-
- sole 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 environ-
- ment variable NCGDB has the same effect.
-
- NCURSES_GPM_TERMS
- 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 envi-
- ronment 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_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.
-
- 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 termi-
- nals by setting this environment variable.
-
- 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 applica-
- tions. 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., tim-
- ing. Unless a hardware terminal is interfaced into a
- terminal concentrator (which does flow control), it
- (or your application) must manage dataflow, prevent-
- ing 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.
-
- 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.
-
- NCURSES_NO_SETBUF
- This setting is obsolete. Before changes
-
- o started with 5.9 patch 20120825 and
-
- o continued though 5.9 patch 20130126
-
- ncurses enabled buffered output during terminal ini-
- tialization. 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 vari-
- able disabled output buffering, leaving the output in
- the original (usually line buffered) mode.
-
- In the current implementation, ncurses performs its
- own buffering and does not require this workaround.
- It does not modify the buffering of the standard out-
- put.
-
- 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
- do not.
-
- NCURSES_NO_UTF8_ACS
- During initialization, the ncurses library checks for
- special cases where VT100 line-drawing (and the cor-
- responding 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 termi-
- nal emulators.
-
- When setting this variable, you should set it to a
- nonzero value. Setting it to zero (or to a nonnum-
- ber) 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 com-
- piled 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,
- 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 name "U8" is chosen to be two characters, to per-
- mit it to be used by applications that use ncurses'
- termcap interface.
-
- 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.
-
- 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.
-
- TERM 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 def-
- initions.
-
- 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 termi-
- nal. 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.
-
- TERMCAP
- If the ncurses library has been configured with term-
- cap 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.
-
- 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:
-
- o the last directory to which ncurses wrote, if
- any, is searched first
-
- o the directory specified by the TERMINFO environ-
- ment variable
-
- o $HOME/.terminfo
-
- o directories listed in the TERMINFO_DIRS environ-
- ment variable
-
- o one or more directories whose names are config-
- ured and compiled into the ncurses library, i.e.,
-
- o /usr/local/ncurses/share/ter-
- minfo:/usr/share/terminfo (corresponding to
- the TERMINFO_DIRS variable)
-
- o /usr/share/terminfo (corresponding to the
- TERMINFO variable)
-
- TERMINFO_DIRS
- Specifies a list of directories to search for termi-
- nal descriptions. The list is separated by colons
- (i.e., ":") on Unix, semicolons on OS/2 EMX.
-
- All of the terminal descriptions are in terminfo
- form. Normally these are stored in a directory tree,
- using subdirectories named by the first letter of the
- terminal names therein.
-
- If ncurses is built with a hashed database, then each
- entry in this list can also be the path of the corre-
- sponding database file.
-
- If ncurses is built with a support for reading term-
- cap files directly, then an entry in this list may be
- the path of a termcap file.
-
- 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.
-
- If the TERMPATH environment variable is not set,
- ncurses looks in the files /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
- $HOME.
+ o If the value of TERMINFO begins with "hex:" or "b64:", ncurses uses
+ the remainder of the value as a compiled terminfo description. You
+ might produce the base64 format using infocmp(1m).
+ TERMINFO=$(infocmp -0 -Q2 -q)
+ export TERMINFO
-
-
ALTERNATE CONFIGURATIONS
- 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 using ncurses:
+ The compiled description is used 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.
+
+ o the last terminal database to which the running ncurses application
+ wrote, if any
+
+ o the location specified by the TERMINFO environment variable
+
+ o$HOME/.terminfo
- --disable-overwrite
- The standard include for ncurses is as noted in SYN-
- OPSIS:
+ o locations listed in the TERMINFO_DIRS environment variable
- #include<curses.h>
+ o location(s) configured and compiled into ncurses
- 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.,
+ o/usr/share/terminfo
- #include<ncurses/curses.h>
- It also omits a symbolic link which would allow you
- to use -lcurses to build executables.
+
+ 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.
- --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
- -lncurses
+
+ 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.
+
+
+
+ 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
+ The standard include for ncurses is as noted in SYNOPSIS:
+
+ #include<curses.h>
+
+ 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.,
+
+ #include<ncurses/curses.h>
+
+ It also omits a symbolic link which would allow you to use
+ -lcurses to build executables.
+
+ --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
+
+ -lncurses
you link with
- -lncursesw
-
- You must also define _XOPEN_SOURCE_EXTENDED when com-
- piling 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 struc-
- ture 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.
-
- --with-pthread
- The configure script renames the library. All of the
- library names have a "t" appended to them (before any
- "w" added by --enable-widec).
-
- 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.
-
- --with-shared
-
- --with-normal
-
- --with-debug
-
- --with-profile
- The shared and normal (static) library names differ
- by their suffixes, e.g., libncurses.so and libn-
- curses.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.
-
- --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 assum-
- ing it is always in the debug library.
+ -lncursesw
+ You must also enable the wide-character features in the header
+ file when compiling for the wide-character library to use the
+ extended (wide-character) functions. The symbol which enables
+ these features has changed since X/Open Curses, Issue 4:
-
-
FILES
- /usr/share/tabset
- directory containing initialization files for the
- terminal capability database /usr/share/terminfo ter-
- minal capability database
+ o Originally, the wide-character feature required the symbol
+ _XOPEN_SOURCE_EXTENDED but that was only valid for XPG4
+ (1996).
+ o Later, that was deemed conflicting with _XOPEN_SOURCE defined
+ to 500.
-
-
SEE ALSO
- terminfo(5) and related pages whose names begin "curs_"
- for detailed routine descriptions.
- curs_variables(3x)
+ o As of mid-2018, none of the features in this implementation
+ require a _XOPEN_SOURCE feature greater than 600. However,
+ X/Open Curses, Issue 7 (2009) recommends defining it to 700.
+ o Alternatively, you can enable the feature by defining
+ NCURSES_WIDECHAR with the caveat that some other header file
+ than curses.h may require a specific value for _XOPEN_SOURCE
+ (or a system-specific symbol).
-
-
EXTENSIONS
- The ncurses library can be compiled with an option
- (-DUSE_GETCAP) that falls back to the old-style /etc/term-
- cap 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) man-
- ual pages for details.
-
- The ncurses library can exploit the capabilities of termi-
- nals which implement the ISO-6429 SGR 39 and SGR 49 con-
- trols, 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 col-
- ored text on a background whose color is set indepen-
- dently, 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 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 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.
-
-
PORTABILITY
- The ncurses library is intended to be BASE-level confor-
- mant with XSI Curses. The EXTENDED XSI Curses functional-
- ity (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 applica-
- tion 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:
-
- o The routine has_key is not part of XPG4, nor is it
- present in SVr4. See the curs_getch(3x) manual page
- for details.
-
- o The routine slk_attr is not part of XPG4, nor is it
- present in SVr4. See the curs_slk(3x) manual page for
- details.
-
- o The routines getmouse, mousemask, ungetmouse, mousein-
- terval, 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.
-
- o The routine mcprint was not present in any previous
- curses implementation. See the curs_print(3x) manual
- page for details.
-
- o The routine wresize is not part of XPG4, nor is it
- present in SVr4. See the wresize(3x) manual page for
- details.
-
- o The WINDOW structure's internal details can be hidden
- from application programs. See curs_opaque(3x) for
- the discussion of is_scrollok, etc.
-
- o This implementation can be configured to provide rudi-
- mentary support for multi-threaded applications. See
- curs_threads(3x) for details.
-
- o 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 capa-
- bilities cr, ind, cub1, ff and tab activated corresponding
- delay bits in the UNIX tty driver. In this implementa-
- tion, all padding is done by sending NUL bytes. This
- method is slightly more expensive, but narrows the inter-
- face to the UNIX kernel significantly and increases the
- package's portability correspondingly.
+ --with-pthread
+ The configure script renames the library. All of the library
+ names have a "t" appended to them (before any "w" added by
+ --enable-widec).
+ 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.
-
-
NOTES
- The header file <curses.h> automatically includes the
- header files <stdio.h> and <unctrl.h>.
+ --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.
- 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 fea-
- ture of AT&T System V Release 3 curses.
+ --with-termlib
+ Low-level functions which do not depend upon whether the library
+ supports wide-characters, are provided in the tinfo library.
+ By doing this, it is possible to share the tinfo library between
+ wide/normal configurations as well as reduce the size of the
+ library when only low-level functions are needed.
-
-
AUTHORS
- Zeyd M. Ben-Halim, Eric S. Raymond, Thomas E. Dickey.
- Based on pcurses by Pavel Curtis.
+ Those functions are described in these pages:
+
+ ocurs_extend(3x) - miscellaneous curses extensions
+
+ ocurs_inopts(3x) - curses input options
+
+ ocurs_kernel(3x) - low-level curses routines
+
+ ocurs_termattrs(3x) - curses environment query routines
+
+ ocurs_termcap(3x) - curses emulation of termcap
+
+ ocurs_terminfo(3x) - curses interface to terminfo database
+
+ ocurs_util(3x) - miscellaneous curses utility routines
+
+ --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.
+
+
+
+ X/Open Curses permits most functions it specifies to be made available
+ as macros as well. ncurses does so
+
+ o for functions that return values via their parameters,
+
+ o to support obsolete features,
+
+ o to reuse functions (for example, those that move the cursor before
+ another operation), and
+
+ o 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.
+
+
+
+ ncurses enables an application to capture mouse events on certain
+ terminals, including xterm(1); see curs_mouse(3x).
+
+ ncurses provides a means of responding to window resizing events, as
+ when running in a GUI terminal emulator application such as xterm; see
+ resizeterm(3x) and wresize(3x).
+
+ ncurses allows an application to query the terminal for the presence of
+ a wide variety of special keys; see has_key(3x).
+
+ 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(3x), key_defined(3x),
+ keybound(3x), and keyok(3x).
+
+ 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(3x).
+
+ An ncurses application can eschew knowledge of WINDOW structure
+ internals, instead using accessor functions such as is_scrollok(3x).
+
+ ncurses enables an application to direct application output to a
+ printer attached to the terminal device; see curs_print(3x).
+
+ ncurses offers slk_attr(3x) as a counterpart of attr_get(3x) for soft-
+ label key lines, and extended_slk_color(3x) as a form of slk_color(3x)
+ that can gather color information from them when many colors are
+ supported.
+
+ Some extensions are available only if ncurses permits modification of
+ unctrl(3x)'s behavior; see use_legacy_coding(3x). ncurses is compiled
+ to support them; section "ALTERNATE CONFIGURATIONS" describes how.
+
+ o Rudimentary support for multi-threaded applications may be
+ available; see curs_threads(3x).
+
+ o Functions that ease the management of multiple screens can be
+ exposed; see curs_sp_funcs(3x).
+
+ o To aid applications to debug their memory usage, ncurses optionally
+ offers functions to more aggressively free memory it dynamically
+ allocates itself; see curs_memleaks(3x).
+
+ o The library facilitates auditing and troubleshooting of its
+ behavior; see curs_trace(3x).
+
+ o The compiler option -DUSE_GETCAP causes the library to fall back to
+ reading /etc/termcap if the terminal setup code cannot find a term-
+ info 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.
+
+
+
+ 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.
+
+
+
+ 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. Relying on this (or some
+ other) extension adversely affects the portability of curses
+ applications.
+
+
+
+ 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.
+
+
+
+ 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.
+
+ o Starting with 4BSD curses (1980) all implementations have 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.
+
+ o 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.
+
+ o X/Open Curses and SVr4 curses are inconsistent with respect to
+ unctrl.h.
+
+ As noted in curs_util(3x), ncurses includes unctrl.h from curses.h
+ (as SVr4 does).
+
+ o 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.
+
+ o X/Open Curses says that curses.hmay 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 module. Very old
+ versions of AIX curses required inclusion of curses.h before
+ term.h.
+
+ 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. But for portability, you
+ should include curses.h before term.h.
+
+ o 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.hmay 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.
+
+ o 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.
+
+
+