Manual Pages  — curs_inopts

 cbreak,  echo,  halfdelay,  intrflush,  is_cbreak,  is_echo,  is_nl,  is_raw,  keypad,  meta,  nl,  nocbreak,  nodelay,  noecho,  nonl,  noqiflush,  noraw,  notimeout,  qiflush,  raw,  timeout,  wtimeout,  typeahead - get and set curses terminal input options

SYNOPSIS DESCRIPTION cbreak, nocbreak echo, noecho halfdelay intrflush keypad meta nl, nonl nodelay notimeout raw, noraw qiflush, nqiflush timeout, wtimeout typeahead RETURN VALUE NOTES EXTENSIONS PORTABILITY HISTORY SEE ALSO

#include <curses.h>

int cbreak(void);
int nocbreak(void);

int echo(void);
int noecho(void);

int intrflush(WINDOW *win, bool bf);
int keypad(WINDOW *win, bool bf);
int meta(WINDOW *win, bool bf);
int nodelay(WINDOW *win, bool bf);
int notimeout(WINDOW *win, bool bf);

int nl(void);
int nonl(void);

int raw(void);
int noraw(void);

void qiflush(void);
void noqiflush(void);

int halfdelay(int tenths);
void timeout(int delay);
void wtimeout(WINDOW *win, int delay);

int typeahead(int fd);

/* extensions */
int is_cbreak(void);
int is_echo(void);
int is_nl(void);
int is_raw(void);

 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.

Initially the terminal may or may not be in  cbreak mode, as the mode is inherited; therefore, a program should call  cbreak or  nocbreak explicitly. Most interactive programs using curses set the  cbreak mode. Note that  cbreak overrides raw. [See  curs_getch(3X) for a 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 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.]

The  halfdelay routine is used for half-delay mode, which is similar to  cbreak mode in that characters typed by the user are immediately available to the program. However, after blocking for tenths tenths of seconds, ERR is returned if nothing has been typed. The value of tenths must be a number between 1 and 255. Use  nocbreak to leave half-delay mode.

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 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 terminal driver settings. The win argument is ignored.

The  keypad option enables the keypad of the user's terminal. If enabled (bf is TRUE), the user can press a function key (such as an arrow key) and  wgetch(3X) returns a single value representing the function key, as in  KEY_LEFT. If disabled (bf is FALSE), curses does not treat function keys specially and the program has to interpret the escape sequences itself. If the keypad in the terminal can be turned on (made to transmit) and off (made to work locally), turning on this option causes the terminal keypad to be turned on when  wgetch(3X) is called. The default value for keypad is FALSE.

Initially, whether the terminal returns 7 or 8 significant bits on 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.

The  nodelay option causes  getch to be a non-blocking call. If no input is ready,  getch returns ERR. If disabled (bf is FALSE),  getch waits until a key is pressed.

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 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 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 flushed when these control characters are read. You may want to call  noqiflush in a signal handler if you want output to continue as though 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, 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).

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  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 is -1, then no typeahead checking is done.

All routines that return an integer return ERR upon failure and OK (SVr4 specifies only an integer value other than ERR) upon successful completion, unless otherwise noted in the preceding routine descriptions.

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.

echo,  noecho,  halfdelay,  intrflush, meta, nl, nonl,  nodelay,  notimeout,  noqiflush,  qiflush,  timeout, and  wtimeout may be implemented as macros.

 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.

 ncurses provides four is_ functions that may be used to detect if the corresponding flags were set or reset.

In each case, the function returns

1	if the flag is set,
0	if the flag is reset, or
-1	if the library is not initialized.

They were designed for  ncurses(3X), and are not found in SVr4 curses, 4.4BSD curses, or any other previous curses implementation.

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(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 curses  wgetch 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. 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 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.

 curses(3X),  curs_getch(3X),  curs_initscr(3X),  curs_util(3X),  define_key(3X),  termios(3)