- 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 6.4 (patch 20231217).
-
- The ncurses library emulates the curses library of System V Release 4
- Unix ("SVr4"), 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.
-
- ncurses man pages employ several sections to clarify matters of usage
+ 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 20240622).
+
+ ncurses permits control of the terminal screen's contents; abstraction
+ and subdivision thereof with windows and pads; acquisition of keyboard
+ and mouse events; control of terminal input and output options;
+ selection of color and rendering attributes (such as bold or
+ underline); the definition and use of softlabel keys; access to the
+ terminfo terminal capability database; a termcap compatibility
+ interface; and an abstraction of the system's API for manipulating the
+ terminal (such as termios(3)).
+
+ ncurses implements the interface described by X/Open Curses Issue 7.
+ In many behavioral details not standardized by X/Open, ncurses emulates
+ the curses library of SVr4 and provides numerous useful extensions.
+
+ ncurses man pages employ several sections to clarify matters of usage
and interoperability with other curses implementations.
- o "NOTES" describes matters 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 for a function (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 "NOTES" describes issues and caveats of which any user of the
+ ncurses API should be aware, such as limitations on the size of an
+ underlying integral type or the availability of a preprocessor
+ macro exclusive of a function definition (which prevents its
+ address from being taken). This section also describes
+ implementation details of significance to the programmer but which
+ are not standardized.
o "EXTENSIONS" presents ncurses innovations beyond the X/Open Curses
standard and/or the SVr4 curses implementation. They are termed
@@ -86,7 +94,7 @@
state.
o "PORTABILITY" discusses matters (beyond the exercise of extensions)
- that should be considered when writing to a curses standard, or to
+ 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
@@ -94,231 +102,242 @@
where precedent or inertia have frustrated better design (and, in a
few cases, where such inertia has been overcome).
- 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
- ALTERNATECONFIGURATIONS.
+ A curses application must be linked with the library; use the -lncurses
+ option to your compiler or linker. A debugging version of the library
+ may be available; if so, link with it using -lncurses_g. (Your system
+ integrator may have installed these libraries such that you can use the
+ options -lcurses and -lcurses_g, respectively.) The ncurses_g library
+ logs events describing ncurses actions to a file called trace in the
+ current directory. See section "ALTERNATE CONFIGURATIONS" below.
- 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(3):
-
- setlocale(LC_ALL,"");
+ 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.
+ 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.
- 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
- exiting.
+ 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), the following sequence should be
- used:
+ To get character-at-a-time input without echoing--most interactive,
+ screen-oriented programs want this--use the following sequence.
- initscr();cbreak();noecho();
+ initscr(); cbreak(); noecho();
- Most programs would additionally use the sequence:
+ Most applications would perform further setup as follows.
- intrflush(stdscr,FALSE);
- keypad(stdscr,TRUE);
+ noqiflush();
+ 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 tputinit command after the shell
- environment variable TERM has been exported. (The BSD-style tset(1)
- utility also performs this function.) See subsection "Tabs and
- Initialization" of terminfo(5).
+ 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. (See panel(3x)
- if you desire this.) 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.
+ A curses library abstracts the terminal with a SCREEN data structure,
+ and represents all or part of its display with WINDOW structures.
+ Distinct properties apply to each; for example, the linediscipline of
+ a typical Unix terminal driver is in one of three modes: raw, cbreak,
+ or normal ("cooked"). In curses, the line discipline is a property of
+ the screen, applying identically to all windows associated with it.
+
+ A window is a rectangular grid of character cells, addressed by line
+ and column coordinates (y, x), with the upper left corner as (0, 0). A
+ window called stdscr, 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. As a rule,
- window-addressing functions feature names prefixed (or infixed, see
- below) with "w"; these allow the user to specify a pointer to a WINDOW.
- Counterparts not thus prefixed (or infixed) affect stdscr. Because
- moving the cursor prior to another operation is so common, curses
- generally also provides functions with a "mv" prefix as a convenience.
- Thus, the library defines all of addch, waddch, mvaddch, and mvwaddch.
- When both prefixes are present, the order of arguments is a WINDOW
- pointer first, then a y and x coordinate pair.
-
- Updating the terminal screen with every curses call can cause
- unpleasant flicker or inefficient use of the communications channel to
- the device. 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. ncursesoptimizes 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 symbols for a small set of line graphics characters,
- corresponding to the VT100 line drawing set. See waddch(3x) and
- wadd_wch(3x).
-
- curses is implemented using the operating system's terminal driver;
- keystroke events are not received 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).
-
-
-
- The selection of an approprate 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 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
+ the cell within it at which the next operation will occur. Among
+ those, the most basic are move(3x) and addch(3x): these place the
+ cursor within and write a character to stdscr, respectively.
+
+ Frequent changes to the terminal screen can cause unpleasant flicker or
+ inefficient use of the communication channel to the device, so as a
+ rule the library does not update it automatically. Therefore, after
+ using curses functions to accumulate a set of desired updates that make
+ sense to present together, call refresh(3x) to tell the library to make
+ the user's screen look like stdscr. The library optimizes its output
+ by computing a minimal volume of operations to mutate the screen from
+ its state at the previous refresh to the new one. Effective
+ optimization demands accurate information about the terminal device:
+ the management of such information is the province of the terminfo(3x)
+ API, a feature of every standard curses implementation.
+
+ Special windows called pads may also be manipulated. These are not
+ constrained to the size of the terminal screen and their contents need
+ not be completely displayed. See curs_pad(3x).
+
+ Many terminals support configuration of character cell foreground and
+ background colors as well as attributes, which cause characters to
+ render in such modes as boldfaced, underlined, or in reverse video.
+ See 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 addch(3x).
+
+ curses is implemented using the operating system's terminal driver; key
+ 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 escape
+ sequence.curses can translate the latter into unique keycodes. See
+ keypad(3x) and getch(3x).
+
+ ncurses provides reimplementations of the SVr4 panel(3x), form(3x), and
+ menu(3x) libraries; they permit overlapping windows and 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 shell's TERM variable, 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.
+ If the environment variable TERMINFO is defined, a curses program
+ checks first for a terminal type description in the location it
+ identifies. TERMINFO is useful for developing type descriptions or
+ when write permission to /usr/share/terminfo is not available.
See section "ENVIRONMENT" below.
- Many curses functions have two or more versions. Those prefixed with
- "w" require a window argument. Four functions prefixed with "p"
- require a pad argument. Those without a prefix generally operate on
- stdscr.
+ 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.
+ parameters. We introduce the character types in the next subsection.
- bfbool (TRUE or FALSE)
- win pointer to WINDOW
- pad pointer to WINDOW that is a pad
+ bf a bool (TRUE or FALSE)
+ c a char or int
+ ch a chtype
+ wc a wchar_t or wint_t
+ wch a cchar_t
+ win pointer to a WINDOW
+ pad pointer to a WINDOW that is a pad
- This manual page describes functions that appear in any configuration
- of the library. There are two common configurations; see section
- "ALTERNATE CONFIGURATIONS" below.
+ This man page primarily surveys 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.
-
- 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.
+ attributes and a color pair in a chtype datum, which is often
+ an alias of int. A string of curses characters is similar to
+ a C char string; a chtype string ends with an integral 0, the
+ null curses character.
+
+ Attributes and a color pair selection (with no corresponding
+ character) can be stored in variables of chtype or attr_t
+ type. In either case, they are accessed via an integral bit
+ mask.
+
+ Each cell of a WINDOW is stored as a chtype. X/Open Curses
+ does not specify the sizes of the character code or color
+ pair identifier, nor the quantity of attribute bits, in
+ chtype; these are implementation-dependent. ncurses uses
+ eight bits for the character code. An application requiring
+ a wider character type, for instance to represent Unicode,
+ should use the wide-character API.
ncursesw is the library in its "wide" configuration, which handles
character encodings requiring a larger data type than char (a
- byte-sized type) can represent. It 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 can fit into an integer. A character code
- may be larger than can fit in a C 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 (row and column) WINDOW is stored as a
- cchar_t.
-
- The setcchar(3x) and getcchar(3x) functions store and
- retrieve the data from a cchar_t structure. The wide library
- API of ncurses depends on two data types standardized by ISO
- C95.
-
- wchar_t stores a wide character. Like chtype, this may be
- an integer. 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 on input, or
- combining, 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 on input.
-
- wint_t can store a wchar_t or the constant WEOF,
- analogously to the int-sized character manipulation
- functions of ISO C and their 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.
+ byte-sized type) can represent. It provides additional
+ functions that complement those in the non-wide library where
+ the size of the underlying character type is significant. A
+ somewhat regular naming convention relates many of the wide
+ variants to their non-wide counterparts; where a non-wide
+ function name contains "ch" or "str", prefix it with "_w" to
+ obtain the wide counterpart. For example, waddch becomes
+ wadd_wch. (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: in the window background management functions,
+ configuration: the window background management function
"bkgd" becomes "bkgrnd"; the window border-drawing and
- -clearing functions are suffixed with "_set".
+ -clearing functions are suffixed with "_set"; and character
+ attribute manipulation functions like "attron" become
+ "attr_on".
+
+ cchar_t corresponds to the non-wide configuration's chtype.
+ It is a structure type because it requires more
+ storage than a standard scalar type offers. A
+ character code may not be representable as a char,
+ and moreover more than one character may occupy a
+ cell (as with accent marks and other diacritics).
+ Each character is of type wchar_t; a complex
+ character contains one spacing character and zero or
+ more non-spacing characters (see below). A string
+ of complex characters ends with a cchar_t whose
+ wchar_t member is the null wide character.
+ Attributes and a color pair selection are stored in
+ separate fields of the structure, not combined into
+ an integer 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.
- 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
- statements).
-
- Functions with a "mv" prefix first perform cursor movement using wmove
- and return an error if the position is outside the window, or (for
- "mvw" functions) if the WINDOW pointer is null. Most "mv"-prefixed
- functions (except variadic functions such as mvprintw) are provided
- both as macros and functions.
-
- Routines that return pointers return NULL on error.
+ Unless otherwise noted, functions that return integers return the
+ constants OK on success and ERR on failure; see curs_variables(3x).
+ 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 environment symbols are useful for customizing the
- runtime behavior of the ncurses library. The most important ones have
- been already discussed in detail.
+ 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).
-
- 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.
+
+ 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 developers to construct repeatable test cases that take
+ into account optimization decisions that depend on baud rate.
- 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.
+
+ 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.
-
- 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.
+ Because this name is also used in development environments to store the
+ C compiler's name, ncurses ignores its value if it is not one character
+ in length.
- 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).
-
- 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.
+ 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.
+ ncurses enforces an upper limit of 512 on each when reading the value.
+ 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.
- 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.
+ 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; ncurses enforces an upper limit of 30,000 (30
+ seconds) when reading the value.
The most common instance where you may wish to change this value is to
- work with 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.
+ 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.
- 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.
+ 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.
- 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.
+ 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.
-
- Tells ncurses where your home directory is. That is where it may read
- and write auxiliary terminal descriptions:
- $HOME/.termcap
- $HOME/.terminfo
+
- Like COLUMNS, specify the height of the screen in characters. See
- COLUMNS for a detailed description.
+ 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.
- 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.
+ (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".
- 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.
+ 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.
-
- 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.
+
+ (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.
- 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".
+ (Linux only) When ncurses is configured to use the GPM interface, this
+ variable may list one or more terminal type names, delimited by
+ vertical bars (|) or colons (:), against which the TERM variable (see
+ below) is matched. An empty value disables the GPM interface, using
+ ncurses's built-in support for xterm(1) mouse protocols instead. If
+ the variable is absent, ncurses attempts to open GPM if TERM contains
+ "linux".
- ncurses may use tabs as part of cursor movement optimization. In some
- cases, your terminal driver may not handle these properly. Set this
- environment variable to any value to disable the feature. You can also
- adjust your stty(1) settings to avoid the problem.
+ ncurses 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.
- 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 to any value.
+ 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 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.
-
- 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.
+ Most terminal type descriptions in the terminfo database detail
+ hardware devices. Many people use curses-based applications in
+ terminal emulator programs that run in a windowing environment. These
+ programs can duplicate all of the important features of a hardware
+ terminal, but often lack their limitations. Chief among these absent
+ drawbacks is the problem of data flow management; that is, limiting the
+ speed of communication to what the hardware could handle. Unless a
+ hardware terminal is interfaced into a terminal concentrator (which
+ does flow control), an application must manage flow itself to prevent
+ overruns and data loss.
+
+ A solution that comes at no hardware cost is for an application to
+ pause 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).
- 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 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 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 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 do not.
+ (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.
- 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. ncurseschecksthe
- TERMenvironmentvariableforthese.Forotherspecialcases,you
- shouldsetthisenvironmentvariable.Doingthistellsncursestouse
- UnicodevalueswhichcorrespondtotheVT100line-drawingglyphs.That
- worksforthespecialcasescited,andislikelytoworkforterminal
- emulators.
-
- 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
+ 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.
@@ -1038,170 +1043,140 @@
xterm-utf8|xterm relying on UTF-8 line-graphics,
U8#1, use=xterm,
- The name "U8" is chosen to be two characters, to permit it to be used
- by applications that use ncurses' termcap interface.
+ The two-character name "U8" was chosen to permit its use via ncurses's
+ 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
- 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.
-
- See curs_trace(3x) for more information.
+ 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.
- 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(1) 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.
+ 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 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.
+ 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.
- ncurses 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
- terminal databases:
-
- o Normally these are stored in a directory tree, using subdirectories
- named by the first letter of the terminal names therein.
-
- 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 database.
+ ncurses can be configured to read terminal type description databases
+ in various locations using different formats. This variable overrides
+ the default location.
- o 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.,
+ 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.
- /usr/share/terminfo.db
+ 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/.
- rather than
+ 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.
- /usr/share/terminfo/
+ o If ncurses is configured with termcap support, this variable may
+ contain the location of a termcap file.
- 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.
+ 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).
- o 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
- file.
+ TERMINFO=$(infocmp -0 -Q2 -q)
+ export TERMINFO
- o 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 infocmp(1m):
+ The compiled description is used only if it corresponds to the
+ terminal type identified by TERM.
- TERMINFO="$(infocmp -0 -Q2 -q)"
- export TERMINFO
+ Setting TERMINFO is the simplest, but not the only, way to direct
+ ncurses to a terminal database. The search path is as follows.
- The compiled description is used if it corresponds to the terminal
- identified by the TERM variable.
+ o the last terminal database to which the running ncurses application
+ wrote, if any
- Setting TERMINFO is the simplest, but not the only way to set location
- of the default terminal database. The complete list of database
- locations in order follows:
+ o the location specified by the TERMINFO environment variable
- o the last terminal database to which ncurses wrote, if any, is
- searched first
+ o$HOME/.terminfo
- o the location specified by the TERMINFO environment variable
+ o locations listed in the TERMINFO_DIRS environment variable
- o $HOME/.terminfo
+ o location(s) configured and compiled into ncurses
- o locations listed in the TERMINFO_DIRS environment variable
-
- o one or more locations whose names are configured and compiled
- into the ncurses library, i.e.,
-
- o /usr/share/terminfo (corresponding to the TERMINFO_DIRS
- variable)
-
- o /usr/share/terminfo (corresponding to the TERMINFO variable)
+ o/usr/share/terminfo
- 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.
+ 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.
- 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
+ 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.
- /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.
+ 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.
- 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:
+ 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:
+ --disable-overwrite
+ The standard C preprocessor inclusion for the curses library is as
+ follows.
#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.,
+ This option is used to avoid file name conflicts between ncurses
+ and an existing curses installation on the system. If ncurses is
+ installed disabling overwrite, it puts its header files in a
+ subdirectory. Here is an example.
#include<ncurses/curses.h>
- It also omits a symbolic link which would allow you to use
- -lcurses to build executables.
+ Installation also omits a symbolic link that would cause the
+ compiler's -lcurses option to link object files with ncurses
+ instead of the system curses library.
- --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"
+ The directory used by this configuration of ncurses is shown in
+ section "SYNOPSIS" above.
+
+ --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
@@ -1210,86 +1185,83 @@
-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 XSI Curses, Issue 4:
+ 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:
- o Originally, the wide-character feature required the symbol
+ 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
+ o Later, that was deemed conflicting with _XOPEN_SOURCE defined
to 500.
- o As of mid-2018, none of the features in this implementation
- require a _XOPEN_SOURCE feature greater than 600. However,
+ 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
+ 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).
- 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
+ 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
+ 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
+ --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
+ 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 libncurses.a. The debug and
- profiling libraries add a "_g" and a "_p" to the root names
+ --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.
- --with-termlib
- Low-level functions which do not depend upon whether the library
+ --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
+ 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.
Those functions are described in these pages:
- ocurs_extend(3x) - miscellaneous curses extensions
+ ocurs_extend(3x) - miscellaneous curses extensions
- ocurs_inopts(3x) - curses input options
+ ocurs_inopts(3x) - curses input options
- ocurs_kernel(3x) - low-level curses routines
+ ocurs_kernel(3x) - low-level curses routines
- ocurs_termattrs(3x) - curses environment query routines
+ ocurs_termattrs(3x) - curses environment query routines
- ocurs_termcap(3x) - curses emulation of termcap
+ ocurs_termcap(3x) - curses emulation of termcap
- ocurs_terminfo(3x) - curses interfaces to terminfo database
+ ocurs_terminfo(3x) - curses interface to terminfo database
- ocurs_util(3x) - miscellaneous curses utility routines
+ 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.
+ --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.
@@ -1303,205 +1275,214 @@
- 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.
+ 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
- See subsection "Header files" below regarding symbols exposed by
+ o in a few special cases.
+
+ If the standard output file descriptor of an ncurses program is
+ redirected to something that is not a terminal device, the library
+ writes screen updates to the standard error file descriptor. This was
+ an undocumented feature of SVr3 curses.
+
+ See subsection "Header Files" below regarding symbols exposed by
inclusion of curses.h.
- 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.
+ ncurses enables an application to capture mouse events on certain
+ terminals, including xterm(1); see curs_mouse(3x).
- 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.
+ 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).
-
- The ncurses library is intended to be BASE-level conformant with XSI
- Curses. The EXTENDED XSI Curses functionality (including color
- support) is supported.
+ 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).
- 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.
+ An ncurses application can eschew knowledge of SCREEN and WINDOW
+ structure internals, instead using accessor functions such as
+ is_cbreak(3x) and is_scrollok(3x).
+ ncurses enables an application to direct its output to a printer
+ attached to the terminal device; see curs_print(3x).
-
- In many cases, X/Open Curses is vague about error conditions, omitting
- some of the SVr4 documentation.
+ 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.
+
+ ncurses permits modification of unctrl(3x)'s behavior; see
+ use_legacy_coding(3x).
+
+ Rudimentary support for multi-threaded applications may be available;
+ see curs_threads(3x).
- 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.
+ Functions that ease the management of multiple screens can be exposed;
+ see curs_sp_funcs(3x).
+ 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).
-
- Most of the extensions provided by ncurses have not been standardized.
- Some have been incorporated into other implementations, such as
- PDCurses or NetBSD curses. Here are a few to consider:
+ The library facilitates auditing and troubleshooting of its behavior;
+ see curs_trace(3x).
- 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.
+ Compiling ncurses with the option -DUSE_GETCAP causes it 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.
- 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.
+ PDCurses and NetBSD curses incorporate some ncurses extensions.
+ Individual man pages indicate where this is the case.
- o 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.
- o The routine mcprint was not present in any previous curses
- implementation. See the curs_print(3x) manual page for details.
+
+ 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.
- o The routine wresize is not part of XPG4, nor is it present in SVr4.
- See the wresize(3x) manual page for details.
+ Differences between X/Open Curses and ncurses are documented in the
+ "PORTABILITY" sections of applicable man pages.
- 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 rudimentary
- support for multi-threaded applications. See curs_threads(3x) for
- details.
+
+ In many cases, X/Open Curses is vague about error conditions, omitting
+ some of the SVr4 documentation.
- 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.
+ Unlike other implementations, ncurses checks pointer parameters, such
+ as those to WINDOW structures, to ensure that they are not null. This
+ is done primarily to guard against programmer error. The standard
+ interface does not provide a way for the library to tell an application
+ which of several possible errors occurred. An application that relies
+ on ncurses to check its function parameters for validity limits its
+ portability and robustness.
-
- 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.
+
+ 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, but does not finish the story:
+ 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>.
+ The inclusion of curses.h may make visible all symbols from the
+ headers stdio.h, term.h, termios.h, and wchar.h.
- Here is a more complete story:
+ but does not finish the story. A more complete account follows.
- o Starting with BSD curses, all implementations have included
- <stdio.h>.
+ o The first curses, in 4BSD, provided a curses.h file.
- BSD curses included <curses.h> and <unctrl.h> from an internal
- header file curses.ext ("ext" abbreviated "externs").
+ BSD curses code included curses.h and unctrl.h from an internal
+ header file curses.ext, where "ext" abbreviated "externs".
- BSD curses used <stdio.h> internally (for printw and scanw), but
- nothing in <curses.h> itself relied upon <stdio.h>.
+ 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(3x), which relies upon <stdio.h>. That
- is, the function prototype uses FILE.
+ 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>.
+ SVr4 curses added putwin and getwin, which also use stdio.h.
- X/Open Curses documents all three of these functions.
+ 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 including <curses.h>. Both document
- curses showing <curses.h> as the only required header.
+ 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> will always include <stdio.h>.
+ As a result, standard curses.h always includes stdio.h.
- o X/Open Curses is inconsistent with respect to SVr4 regarding
- <unctrl.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> (like SVr4).
+ As noted in curs_util(3x), ncurses includes unctrl.h from curses.h
+ (as SVr4 does).
- o X/Open's comments about <term.h> and <termios.h> may refer to HP-UX
- and AIX:
+ 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.
+ 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.
+ AIX curses includes term.h and termios.h. Again, ncurses and
+ Solaris curses do not.
- o X/Open says that <curses.h> may include <term.h>, but there is no
- requirement that it do that.
+ 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 headers in the same module. Very
- old versions of AIX curses required including <curses.h> before
- including <term.h>.
+ 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.
- Because ncurses header files include the headers needed to define
- datatypes used in the headers, ncurses header files can be included
- in any order. But for portability, you should include <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 "maymakevisible" because including a header
- file does not necessarily make all symbols in it visible (there are
- ifdef's to consider).
+ 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, in ncurses <wchar.h> may be included if the proper
+ 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 the header is included, its symbols may be made
- visible. That depends on the value used for _XOPEN_SOURCE feature
- test macro.
-
- o X/Open Curses documents one required header, in a special case:
- <stdarg.h> before <curses.h> to prototype the vw_printw and
- vw_scanw functions (as well as the obsolete the vwprintw and
- vwscanw functions). Each of those uses a va_list parameter.
-
- The two obsolete functions were introduced in SVr3. The other
- functions were introduced in X/Open Curses. In between, SVr4
- curses provided for the possibility that an application might
- include either <varargs.h> or <stdarg.h>. Initially, that was done
- by using void* for the va_list parameter. Later, a special type
- (defined in <stdio.h>) was introduced, to allow for compiler type-
- checking. That special type is always available, because <stdio.h>
- is always included by <curses.h>.
-
- None of the X/Open Curses implementations require an application to
- include <stdarg.h> before <curses.h> because they either have
- allowed for a special type, or (like ncurses) include <stdarg.h>
- directly to provide a portable interface.
+ 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.