- The ncurses library provides several functions which let an application
- change the way input from the terminal is handled. Some are global,
- applying to all windows. Others apply only to a specific window.
- Window-specific settings are not automatically applied to new or
- derived windows. An application must apply these to each window, if
- the same behavior is needed.
-
-
-
- Normally, the tty driver buffers typed characters until a newline or
- carriage return is typed. The cbreak routine disables line buffering
- and erase/kill character-processing (interrupt and flow control
- characters are unaffected), making characters typed by the user
+ ncurses provides several functions that let an application change the
+ way input from the terminal is handled. Some are global, applying to
+ all windows. Others apply only to a specific window. Window-specific
+ settings are not automatically applied to new or derived windows. An
+ application must apply these to each window if the same behavior is
+ desired.
+
+
+
+ Normally, the terminal driver buffers typed characters until a newline
+ or carriage return is typed. The cbreak routine disables line
+ buffering and erase/kill character-processing (interrupt and flow
+ control characters are unaffected), making characters typed by the user
immediately available to the program. The nocbreak routine returns the
terminal to normal (cooked) mode.
@@ -115,15 +115,15 @@
discussion of how these routines interact with echo and noecho.]
-
The echo and noecho routines control whether characters typed by the
- user are echoed by getch(3x) as they are typed. Echoing by the tty
- driver is always disabled, but initially getch is in echo mode, so
- characters typed are echoed. Authors of most interactive programs
- prefer to do their own echoing in a controlled area of the screen, or
- not to echo at all, so they disable echoing by calling noecho. [See
- curs_getch(3x) for a discussion of how these routines interact with
- cbreak and nocbreak.]
+ user are echoed by getch(3x) as they are typed. Echoing by the
+ terminal driver is always disabled, but initially getch is in echo
+ mode, so characters typed are echoed. Authors of most interactive
+ programs prefer to do their own echoing in a controlled area of the
+ screen, or not to echo at all, so they disable echoing by calling
+ noecho. [See curs_getch(3x) for a discussion of how these routines
+ interact with cbreak and nocbreak.]
If the intrflush option is enabled (bf is TRUE), and an interrupt key
is pressed on the keyboard (interrupt, break, quit), all output in the
- tty driver queue will be flushed, giving the effect of faster response
+ terminal driver queue is flushed, giving the effect of faster response
to the interrupt, but causing curses to have the wrong idea of what is
- on the screen. Disabling the option (bf is FALSE) prevents the flush.
- The default for the option is inherited from the tty driver settings.
- The window argument is ignored.
+ on the screen. Disabling the option (bf is FALSE), prevents the flush.
+ The default for the option is inherited from the terminal driver
+ settings. The win argument is ignored.
Initially, whether the terminal returns 7 or 8 significant bits on
- input depends on the control mode of the tty driver [see termios(3)].
- To force 8 bits to be returned, invoke meta(win, TRUE); this is
- equivalent, under POSIX, to setting the CS8 flag on the terminal. To
- force 7 bits to be returned, invoke meta(win, FALSE); this is
- equivalent, under POSIX, to setting the CS7 flag on the terminal. The
- window argument, win, is always ignored. If the terminfo capabilities
- smm (meta_on) and rmm (meta_off) are defined for the terminal, smm is
- sent to the terminal when meta(win, TRUE) is called and rmm is sent
- when meta(win, FALSE) is called.
-
-
-
+ input depends on the control mode of the terminal driver [see
+ termios(3)]. To force 8 bits to be returned, invoke meta(win, TRUE);
+ this is equivalent, under POSIX, to setting the CS8 flag on the
+ terminal. To force 7 bits to be returned, invoke meta(win, FALSE);
+ this is equivalent, under POSIX, to setting the CS7 flag on the
+ terminal. The window argument, win, is always ignored. If the
+ terminfo capabilities smm (meta_on) and rmm (meta_off) are defined for
+ the terminal, smm is sent to the terminal when meta(win, TRUE) is
+ called and rmm is sent when meta(win, FALSE) is called.
+
+
+
The nl and nonl routines control whether the underlying display device
translates the return key into newline on input.
@@ -185,21 +185,21 @@
When interpreting an escape sequence, wgetch(3x) sets a timer while
waiting for the next character. If notimeout(win, TRUE) is called,
then wgetch does not set a timer. The purpose of the timeout is to
- differentiate between sequences received from a function key and those
- typed by a user.
+ distinguish sequences produced by a function key from those typed by a
+ user.
-
The raw and noraw routines place the terminal into or out of raw mode.
Raw mode is similar to cbreak mode, in that characters typed are
immediately passed through to the user program. The differences are
that in raw mode, the interrupt, quit, suspend, and flow control
characters are all passed through uninterpreted, instead of generating
a signal. The behavior of the BREAK key depends on other bits in the
- tty driver that are not set by curses.
+ terminal driver that are not set by curses.
-
When the noqiflush routine is used, normal flush of input and output
queues associated with the INTR, QUIT and SUSP characters will not be
done [see termios(3)]. When qiflush is called, the queues will be
@@ -208,23 +208,23 @@
the interrupt had not occurred, after the handler exits.
-
The timeout and wtimeout routines set blocking or non-blocking read for
- a given window. If delay is negative, blocking read is used (i.e.,
- waits indefinitely for input). If delay is zero, then non-blocking
- read is used (i.e., read returns ERR if no input is waiting). If delay
- is positive, then read blocks for delay milliseconds, and returns ERR
+ a given window. If delay is negative, a blocking read is used (i.e.,
+ waits indefinitely for input). If delay is zero, then a non-blocking
+ read is used (i.e., read returns ERR if no input is waiting). If delay
+ is positive, then read blocks for delay milliseconds, and returns ERR
if there is still no input. Hence, these routines provide the same
functionality as nodelay, plus the additional capability of being able
to block for only delay milliseconds (where delay is positive).
- The curses library does "line-breakout optimization" by looking for
- typeahead periodically while updating the screen. If input is found,
- and it is coming from a tty, the current update is postponed until
+ curses does "line-breakout optimization" by looking for typeahead
+ periodically while updating the screen. If input is found, and it is
+ coming from a terminal, the current update is postponed until
refresh(3x) or doupdate is called again. This allows faster response
- to commands typed in advance. Normally, the input FILE pointer passed
+ to commands typed in advance. Normally, the input FILE pointer passed
to newterm, or stdin in the case that initscr was used, will be used to
do this typeahead checking. The typeahead routine specifies that the
file descriptor fd is to be used to check for typeahead instead. If fd
@@ -237,106 +237,119 @@
completion, unless otherwise noted in the preceding routine
descriptions.
- X/Open does not define any error conditions. In this implementation,
- functions with a window parameter will return an error if it is null.
- Any function will also return an error if the terminal was not
- initialized. Also,
+ X/Open Curses does not specify any error conditions. In this
+ implementation, functions with a window parameter will return an error
+ if it is null. Any function will also return an error if the terminal
+ was not initialized. Also,
halfdelay
returns an error if its parameter is outside the range 1..255.
- Note that echo, noecho, halfdelay, intrflush, meta, nl, nonl, nodelay,
- notimeout, noqiflush, qiflush, timeout, and wtimeout may be macros.
+ echo, noecho, halfdelay, intrflush, meta, nl, nonl, nodelay, notimeout,
+ noqiflush, qiflush, timeout, and wtimeout may be implemented as macros.
- The noraw and nocbreak calls follow historical practice in that they
- attempt to restore to normal ("cooked") mode from raw and cbreak modes
- respectively. Mixing raw/noraw and cbreak/nocbreak calls leads to tty
- driver control states that are hard to predict or understand; it is not
+ noraw and nocbreak follow historical practice in that they attempt to
+ restore normal ("cooked") mode from raw and cbreak modes respectively.
+ Mixing raw/noraw and cbreak/nocbreak calls leads to terminal driver
+ control states that are hard to predict or understand; doing so is not
recommended.
- This implementation provides four functions which may be used to detect
- if the corresponding flags were set or reset:
+ ncurses provides four "is_" functions that may be used to detect if the
+ corresponding flags were set or reset.
- QuerySetReset
- ------------------------------
- is_cbreak cbreak nocbreak
- is_echo echo noecho
- is_nl nl nonl
- is_raw raw noraw
+ QuerySetReset
+ ------------------------------
+ is_cbreak cbreak nocbreak
+ is_echo echo noecho
+ is_nl nl nonl
+ is_raw raw noraw
In each case, the function returns
- 1 if the flag is set,
+ 1 if the flag is set,
- 0 if the flag is reset, or
+ 0 if the flag is reset, or
- -1 if the curses library was not initialized.
+ -1 if the library is not initialized.
- These routines are specific to ncurses. They were not supported on
- Version 7, BSD or System V implementations. It is recommended that any
- code depending on ncurses extensions be conditioned using
- NCURSES_VERSION.
+ They were designed for ncurses(3x), and are not found in SVr4 curses,
+ 4.4BSD curses, or any other previous curses implementation.
- Except as noted in the section on extensions, these functions are
- described in the XSI Curses standard, Issue 4.
-
- The ncurses library obeys the XPG4 standard and the historical practice
- of the AT&T curses implementations, in that the echo bit is cleared
- when curses initializes the terminal state. BSD curses differed from
- this slightly; it left the echo bit on at initialization, but the BSD
- raw call turned it off as a side-effect. For best portability, set
- echo or noecho explicitly just after initialization, even if your
- program remains in cooked mode.
-
- The XSI Curses standard is ambiguous on the question of whether raw
- should disable the CRLF translations controlled by nl and nonl. BSD
- curses did turn off these translations; AT&T curses (at least as late
- as SVr1) did not. We chose to do so, on the theory that a programmer
- requesting raw input wants a clean (ideally 8-bit clean) connection
- that the operating system will not alter.
-
- When keypad is first enabled, ncurses loads the key-definitions for the
- current terminal description. If the terminal description includes
- extended string capabilities, e.g., from using the -x option of tic,
- then ncurses also defines keys for the capabilities whose names begin
- with "k". The corresponding keycodes are generated and (depending on
- previous loads of terminal descriptions) may differ from one execution
+ Applications employing ncurses extensions should condition their use on
+ the visibility of the NCURSES_VERSION preprocessor macro.
+
+ Except as noted in section "EXTENSIONS" above, X/Open Curses, Issue 4,
+ Version 2 describes these functions.
+
+ ncurses follows X/Open Curses and the historical practice of AT&T
+ curses implementations, in that the echo bit is cleared when curses
+ initializes the terminal state. BSD curses differed from this
+ slightly; it left the echo bit on at initialization, but the BSD raw
+ call turned it off as a side effect. For best portability, set echo or
+ noecho explicitly just after initialization, even if your program
+ remains in cooked mode.
+
+ X/Open Curses is ambiguous regarding whether raw should disable the
+ CR/LF translations controlled by nl and nonl. BSD curses did turn off
+ these translations; AT&T curses (at least as late as SVr1) did not.
+ ncurses does so, on the assumption that a programmer requesting raw
+ input wants a clean (ideally, 8-bit clean) connection that the
+ operating system will not alter.
+
+ When keypad is first enabled, ncurses loads the key definitions for the
+ current terminal description. If the terminal description includes
+ extended string capabilities, e.g., from using the -x option of tic,
+ then ncurses also defines keys for the capabilities whose names begin
+ with "k". The corresponding keycodes are generated and (depending on
+ previous loads of terminal descriptions) may differ from one execution
of a program to the next. The generated keycodes are recognized by the
- keyname function (which will then return a name beginning with "k"
- denoting the terminfo capability name rather than "K", used for curses
- key-names). On the other hand, an application can use define_key to
- establish a specific keycode for a given string. This makes it
- possible for an application to check for an extended capability's
- presence with tigetstr, and reassign the keycode to match its own
+ keyname(3x) function (which will then return a name beginning with "k"
+ denoting the terminfo capability name rather than "K", used for curses
+ key names). On the other hand, an application can use define_key(3x)
+ to establish a specific keycode for a given string. This makes it
+ possible for an application to check for an extended capability's
+ presence with tigetstr, and reassign the keycode to match its own
needs.
Low-level applications can use tigetstr to obtain the definition of any
- particular string capability. Higher-level applications which use the
- curseswgetch and similar functions to return keycodes rely upon the
+ particular string capability. Higher-level applications which use the
+ curseswgetch and similar functions to return keycodes rely upon the
order in which the strings are loaded. If more than one key definition
- has the same string value, then wgetch can return only one keycode.
+ has the same string value, then wgetch can return only one keycode.
Most curses implementations (including ncurses) load key definitions in
- the order defined by the array of string capability names. The last
- key to be loaded determines the keycode which will be returned. In
- ncurses, you may also have extended capabilities interpreted as key
- definitions. These are loaded after the predefined keys, and if a
- capability's value is the same as a previously-loaded key definition,
+ the order defined by the array of string capability names. The last
+ key to be loaded determines the keycode which will be returned. In
+ ncurses, you may also have extended capabilities interpreted as key
+ definitions. These are loaded after the predefined keys, and if a
+ capability's value is the same as a previously-loaded key definition,
the later definition is the one used.
+
+ Formerly, ncurses used nl and nonl to control the conversion of
+ newlines to carriage return/line feed on output as well as input.
+ X/Open Curses documents the use of these functions only for input.
+ This difference arose from converting the pcurses source (1986), which
+ used ioctl(2) calls and the sgttyb structure, to termios (the POSIX
+ terminal API). In the former, both input and output were controlled
+ via a single option CRMOD, while the latter separates these features.
+ Because that conversion interferes with output optimization, ncurses
+ 6.2 (2020) amended nl and nonl to eliminate their effect on output.
+
+