cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta,
nodelay, notimeout, raw, noraw, noqiflush, qiflush, timeout, wtimeout,
typeahead - curses input options
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 notimeout(WINDOW *win, bool bf);
void timeout(int delay);
void wtimeout(WINDOW *win, int delay);
int typeahead(int fd);
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 charac‐
ters 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 explic‐
itly. 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 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
The halfdelay routine is used for half-delay mode, which is similar to
cbreak mode in that characters typed by the user are immediately avail‐
able to the program. However, after blocking for tenths tenths of sec‐
onds, 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
If the intrflush option is enabled, (bf is TRUE), when 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
to the interrupt, but causing curses to have the wrong idea of what is
on the screen. Disabling (bf is FALSE), the option prevents the flush.
The default for the option is inherited from the tty driver settings.
The window argument is ignored.
The keypad option enables the keypad of the user's terminal. If en‐
abled (bf is TRUE), the user can press a function key (such as an arrow
key) and wgetch returns a single value representing the function key,
as in KEY_LEFT. If disabled (bf is FALSE), curses does not treat func‐
tion keys specially and the program has to interpret the escape se‐
quences 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 is called. The
default value for keypad is false.
Initially, whether the terminal returns 7 or 8 significant bits on in‐
put depends on the control mode of the tty driver [see termio(7)]. 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 defined for the terminal, smm is sent to the termi‐
nal when meta(win, TRUE) is called and rmm is sent when meta(win,
FALSE) is called.
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 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.
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 imme‐
diately 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.
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 termio(7)]. 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, 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 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 re‐
fresh or doupdate is called again. This allows faster response to com‐
mands 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 descrip‐
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 initial‐
returns an error if its parameter is outside the range
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 pro‐
gram remains in cooked mode.
Note that echo, noecho, halfdelay, intrflush, meta, nodelay, notimeout,
noqiflush, qiflush, timeout, and wtimeout may be 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
SEE ALSOcurses(3X), curs_getch(3X), curs_initscr(3X), termio(7)curs_inopts(3X)