Ubuntu Manpage: cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta, nodelay, notimeout, raw, noraw,

Provided by: ncurses-doc_6.2-0ubuntu2.1_all

NAME

       cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta, nodelay, notimeout, raw, noraw,
       noqiflush, qiflush, timeout, wtimeout, typeahead - curses input options

SYNOPSIS

       #include <curses.h>

       int cbreak(void);
       int nocbreak(void);
       int echo(void);
       int noecho(void);
       int halfdelay(int tenths);
       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 raw(void);
       int noraw(void);
       void noqiflush(void);
       void qiflush(void);
       int notimeout(WINDOW *win, bool bf);
       void timeout(int delay);
       void wtimeout(WINDOW *win, int delay);
       int typeahead(int fd);

DESCRIPTION

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.

cbreak
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 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(3X) as they
are typed. Echoing by the tty driver is always disabled, but initially getch is in echo mode, so charac‐
ters typed are echoed. Authors of most interactive programs prefer to do their own echoing in a con‐
trolled 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 (inter‐
rupt, break, quit), all output in the tty driver queue will be flushed, giving the effect of faster re‐
sponse 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.

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(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.

meta
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 equiva‐
lent, 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 de‐
fined 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.

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.

While interpreting an input escape sequence, wgetch(3X) sets a timer while waiting for the next charac‐
ter. 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.

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 unin‐
terpreted, 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.

noqiflush
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 neg‐
ative, 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 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 millisec‐
onds (where delay is positive).

typeahead
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 re‐
fresh(3X) or doupdate is called again. This allows faster response to commands typed in advance. Nor‐
mally, 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  descrip‐
       tions.

       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  ini‐
       tialized.  Also,

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

PORTABILITY

       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 implementa‐
       tions, 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.

       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 key‐
       codes are generated and (depending on previous loads of terminal descriptions) may differ from one execu‐
       tion 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 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 defin‐
       itions in the order defined by the array of string capability names.  The last key to  be  loaded  deter‐
       mines the keycode which will be returned.  In ncurses, you may also have extended capabilities interpret‐
       ed  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.

NOTES