noecho
curs_inopts(3X) curs_inopts(3X)
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
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 char-
acters are unaffected), making characters typed by the user immedi-
ately available to the program. The nocbreak routine returns the ter-
minal 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 dis-
cussion 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 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), 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 pre-
vents 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
enabled (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
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 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 driver [see termio(7)].
To force 8 bits to be returned, invoke meta(win, TRUE); this is equiv-
alent, 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 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 posi-
tive).
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.
RETURN VALUE
All routines that return an integer return ERR upon failure and OK
(SVr4 specifies only "an integer value other than ERR") upon success-
ful completion, unless otherwise noted in the preceding routine
descriptions.
PORTABILITY
These functions are described in the XSI Curses standard, Issue 4.
The ncurses library obeys the XPG4 standard and the historical prac-
tice of the AT&T curses implementations, in that the echo bit is
cleared when curses initializes the terminal state. BSD curses dif-
fered 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 porta-
bility, set echo or noecho explicitly just after initialization, even
if your program remains in cooked mode.
NOTES
Note that echo, noecho, halfdelay, intrflush, meta, nodelay, notime-
out, 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 recommended.
SEE ALSO
curses(3X), curs_getch(3X), curs_initscr(3X), termio(7)
curs_inopts(3X)
