Ubuntu Manpage: cbreak, echo, halfdelay, intrflush, is_cbreak, is_echo, is_nl, is

Provided by: ncurses-doc_6.4+20240113-1ubuntu2_all

NAME

       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

       #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);

DESCRIPTION

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.

cbreak, nocbreak
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 getch(3NCURSES) for a discussion of how these routines interact
with echo and noecho.]

echo, noecho
The echo and noecho routines control whether characters typed by the user are echoed by getch(3NCURSES)
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 getch(3NCURSES) for a discussion of how these routines interact with cbreak and nocbreak.]

halfdelay
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.

intrflush
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.

keypad
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(3NCURSES) 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(3NCURSES) is called. The default value for keypad is FALSE.

meta
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.

nl, nonl
The nl and nonl routines control whether the underlying display device translates the return key into
newline on input.

nodelay
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.

notimeout
When interpreting an escape sequence, wgetch(3NCURSES) 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.

raw, noraw
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.

qiflush, nqiflush
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.

timeout, wtimeout
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).

typeahead
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(3NCURSES) 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.

RETURN VALUE

       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  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,

          halfdelay
               returns an error if its parameter is outside the range 1..255.

NOTES

       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.

EXTENSIONS

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

                                             Query       Set      Reset
                                             ──────────────────────────────
                                             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,

       0   if the flag is reset, or

       -1  if the library is not initialized.

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

PORTABILITY

       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(3NCURSES)
       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(3NCURSES)  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.