- 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 20240120).
-
- 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 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
+ 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
+ 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 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
+ 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 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 section "ALTERNATE
- CONFIGURATIONS" below.
+ 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.
-
- 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 constants for a small set of line-drawing and other
- graphics corresponding to the DEC Alternate Character Set (ACS), a
- feature of VT100 and other terminals. See waddch(3x) and wadd_wch(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).
-
-
-
- The selection of an appropriate value of TERM in the process
+ 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 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
+ 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
+ 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, 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.
+ 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 fits into an integral 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.
-
- 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, it may be an
- alias of int. Depending on the character encoding,
- a wide character may be spacing, meaning that it
+ 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: 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".
+
+ 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,
+ 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
@@ -293,20 +327,6 @@
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.
-
- 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,
- "bkgd" becomes "bkgrnd"; the window border-drawing and
- -clearing functions are suffixed with "_set".
-
- 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 with a "mv" prefix first perform cursor movement using wmove
- and fail if the position is outside the window, or (for "mvw"
- functions) if the WINDOW pointer is null.
+ 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 the command_character (cmdch) capability value of
- loaded terminfo entries to the value of this variable. Very few term-
- info 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.
-
- The most common instance where you may wish to change this value is to
- work with slow hosts, e.g., running on a network. If the host cannot
- read characters rapidly enough, it will have the same effect as if the
- terminal did not send characters rapidly enough. The library will
- still see a timeout.
-
- Note that xterm mouse events are built up from character sequences
- received from the xterm. If your application makes heavy use of
- multiple-clicking, you may wish to lengthen this default value because
- the timeout applies to the composed multi-click event as well as the
- individual clicks.
-
- In addition to the environment variable, this implementation provides a
- global variable with the same name. Portable applications should not
- rely upon the presence of ESCDELAY in either form, but setting the
- environment variable rather than the global variable does not create
- problems when compiling an application.
+ 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 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.
- Tells ncurses where your home directory is. That is where it may read
- and write auxiliary terminal descriptions:
-
- $HOME/.termcap
- $HOME/.terminfo
+ ncurses may read and write auxiliary terminal descriptions in .termcap
+ and .terminfo files in the user's home directory.
- 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
+ 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), 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.
+ does flow control), an application must manage flow itself to prevent
+ overruns and data loss.
- 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.
+ 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(3) 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.
@@ -1025,167 +1043,137 @@
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.
- 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.
+ 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.
+
+ The directory used by this configuration of ncurses is shown in
+ section "SYNOPSIS" above.
- --enable-widec
+ --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"
@@ -1200,7 +1188,7 @@
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:
+ these features has changed since X/Open Curses, Issue 4:
o Originally, the wide-character feature required the symbol
_XOPEN_SOURCE_EXTENDED but that was only valid for XPG4
@@ -1228,7 +1216,7 @@
applications to be built using either library from the same set of
headers.
- --with-pthread
+ --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).
@@ -1238,19 +1226,16 @@
to set these values. Some applications (very few) may require
changes to work with this convention.
- --with-shared
-
- --with-normal
-
- --with-debug
-
- --with-profile
+ --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
+ --with-termlib
Low-level functions which do not depend upon whether the library
supports wide-characters, are provided in the tinfo library.
@@ -1274,7 +1259,7 @@
ocurs_util(3x) - miscellaneous curses utility routines
- --with-trace
+ --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
@@ -1300,23 +1285,23 @@
o to reuse functions (for example, those that move the cursor before
another operation), and
- o a few special cases.
+ 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.
+ an undocumented feature of SVr3 curses.
- See subsection "Header files" below regarding symbols exposed by
+ 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; see curs_mouse(3x).
+ 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
+ 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
@@ -1324,8 +1309,8 @@
ncurses extends the fixed set of function key capabilities specified by
X/Open Curses by allowing the application programmer to define
- additional key sequences at runtime; see define_key(3x),
- key_defined(3x), and keyok(3x).
+ 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
@@ -1334,43 +1319,51 @@
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 choose to hide the internal details of
- WINDOW structures, instead using accessor functions such as
- is_scrollok(3x).
+ 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 application output to a
- printer attached to the terminal device; see curs_print(3x).
+ ncurses enables an application to direct its 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 only available if ncurses is compiled to support
- them; see section "ALTERNATE CONFIGURATIONS" above.
+ 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).
+
+ Functions that ease the management of multiple screens can be exposed;
+ see curs_sp_funcs(3x).
- o Rudimentary support for multi-threaded applications may be
- available; see curs_threads(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).
- o Functions that ease the management of multiple screens can be
- exposed; see curs_sp_funcs(3x).
+ 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.
+ 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.
- PDCurses and NetBSD curses incorporate some ncurses extensions.
+ 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 nearly all its enhanced features.
+ 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.
@@ -1380,113 +1373,116 @@
In many cases, X/Open Curses is vague about error conditions, omitting
some of the SVr4 documentation.
- 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.
+ 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
+ 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
- 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.
+ 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 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.
+ 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).
- 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>.
+ 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.
- 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.
+ 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.