curs_inopts, cbreak, nocbreak, echo, noecho, halfdelay, intrflush, key‐
pad, meta, nodelay, qiflush, noqiflush, raw, noraw, timeout, notimeut,
wtimeout, typeahead - Curses routines that control terminal-input
void ); int nocbreak(
void ); int echo(
void ); int noecho(
void ); int halfdelay(
int tenths ); int intrflush(
bool bf ); int keypad(
bool bf ); int meta(
bool bf ); int nodelay(
bool bf ); int raw(
void ); int noraw(
void ); void qiflush(
void ); void noqiflush(
void ); void timeout(
int delay ); int notimeout(
bool bf ); void wtimeout(
int delay ); int typeahead(
int fd );
Curses Library (libcurses)
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta,
nodelay, qiflush, noqiflush, raw, noraw, timeout, notimeout, wtimeout,
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
The cbreak and nocbreak routines put the terminal into and out of
cbreak mode, respectively. In this mode, characters typed by the user
are immediately available to the program, and erase/kill character-pro‐
cessing is not performed. When out of this mode, the tty driver buffers
the typed characters until the user types a newline or carriage return.
Interrupt and flow-control characters are unaffected by this mode. Ini‐
tially, 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(3) 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
are echoed as they are typed. 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(3) for a discussion of how these routines interact with
cbreak and nocbreak.)
The halfdelay routine sets 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,
halfdelay returns ERR if nothing has been typed. The value of tenths
must be a number between 1 and 255. Applications call the nocbreak rou‐
tine to leave half-delay mode.
If the intrflush routine enables or disables the intrflush option. When
intrflush is enabled (bf is set to TRUE), all output in the tty driver
queue is flushed when the user presses an interrupt key (interrupt,
break, or quit). This flush operation gives the effect of faster
response to the interrupt but causes Curses to have the wrong image of
what is on the screen. Disabling the intrflush option (setting bf to
FALSE) prevents output in the tty driver queue from being flushed. The
default for the intrflush option is inherited from the tty driver set‐
tings. The window argument is ignored.
The keypad routine enables the keypad option associated with the user's
terminal. If the keypad option is enabled (bf is set to 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 the key‐
pad is disabled (bf is set to FALSE), Curses does not treat function
keys specially, and the program has to interpret the escape sequences.
If the keypad in the terminal can be turned on (made to transmit) and
off (made to work locally), enabling the keypad option causes the ter‐
minal 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 termios(4)).
To force 8 bits to be returned, applications call meta(win, TRUE). To
force 7 bits to be returned, applications call meta(win, FALSE). The
window argument, win, is always ignored. If the terminfo database capa‐
bilities 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 routine enables and disables no delay mode. When this mode
is enabled (bf is set to TRUE), the call causes getch to be a nonblock‐
ing call. In this case, if no input is ready, getch returns ERR. If no
delay mode is disabled (bf is FALSE), getch waits until the user
presses a key.
While interpreting an input escape sequence, wgetch sets a timer while
waiting for the next character. If the application calls notimeout(win,
TRUE), then wgetch does not set a timeout interval. 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 in and out of raw mode.
Raw mode is similar to cbreak mode in that the typed characters are
immediately passed through to the user program. The difference is that
in raw mode, the interrupt, quit, suspend, and flow control characters
do not generate a signal but are all passed through uninterpreted to
the application. The behavior of the Break key depends on other bits in
the tty driver that are not set by Curses.
When applications use the noqiflush routine, Curses sets the NOFLSH
condition in the tty driver to disable queue flushing. In this state,
the normal flushing of input and output queues associated with the quit
and interrupt characters is not done. (see termios(4)). When the appli‐
cation calls qiflush, Curses flushes the queues when the quit and
interrupt characters are read.
The timeout and wtimeout routines set blocking or nonblocking read for
a given window. If delay is negative, blocking read is set; that is,
the read operation waits indefinitely for input. If delay is zero, then
nonblocking read is set; that is, the read operation returns ERR if no
input is waiting. If delay is positive, then the read operation blocks
for delay milliseconds, then returns ERR if there is still no input.
Therefore, the timeout and wtimeout routines provide the same function‐
ality as nodelay, plus (where delay is positive) the additional capa‐
bility of being able to block for only a specified number of millisec‐
Curses performs “line-breakout optimization” by looking periodically
for typeahead input while updating the screen. If input is found, and
it is coming from a tty, Curses postpones the screen update until
refresh or doupdate is called again. This optimization allows faster
response to commands typed in advance. To do the typeahead checking,
Curses normally uses the input FILE pointer passed to newterm, or stdin
if initscr was called. The typeahead routine tells Curses to check for
typeahead input by using the specified file descriptor, fd. If fd is
-1, then Curses performs no typeahead checking.
The header file <curses.h> automatically includes the header file
Note that echo, noecho, and timeout may be macros.
All routines that return an integer return ERR upon failure and OK upon
successful completion, unless otherwise noted in the preceding routine
Functions: curses(3), curs_getch(3), curs_initscr(3)