cbreak, nocbreak, echo, noecho, halfdelay, intrflush,
keypad, meta, nodelay, notimeout, raw, noraw, noqiflush,
qiflush, timeout, wtimeout, typeahead - curses input
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-process-
ing (interrupt and flow control characters are unaffect-
ed), 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 over-
rides 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 initial-
ly 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 re-
turned if nothing has been typed. The value of tenths
must be a number between 1 and 255. Use nocbreak to leave
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 in-
terrupt, 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 inher-
ited from the tty driver settings. The window argument is
The keypad option enables the keypad of the user's termi-
nal. If enabled (bf is TRUE), the user can press a func-
tion key (such as an arrow key) and wgetch returns a sin-
gle 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 local-
ly), 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 input depends on the control mode of the tty driv-
er [see termio(7)]. To force 8 bits to be returned, in-
voke 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 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 notime-
out(win, TRUE) is called, then wgetch does not set a
timer. The purpose of the timeout is to differentiate be-
tween 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 immediately passed through to the us-
er program. The differences are that in raw mode, the in-
terrupt, 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 in-
put). 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 rou-
tines provide the same functionality as nodelay, plus the
additional capability of being able to block for only de-
lay 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 refresh 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 fail-
ure 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 im-
plementation, functions with a window parameter will re-
turn an error if it is null. Any function will also re-
turn an error if the terminal was not initialized. Also,
returns an error if its parameter is outside
the range 1..255.
These functions are described in the XSI Curses standard,
The ncurses library obeys the XPG4 standard and the his-
torical 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 portabili-
ty, set echo or noecho explicitly just after initializa-
tion, even if your program remains in cooked mode.
Note that echo, noecho, halfdelay, intrflush, meta, node-
lay, 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
curses(3x), curs_getch(3x), curs_initscr(3x), termio(7)
Man(1) output converted with