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 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.]
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
getch(3NCURSES)
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 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 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 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
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
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 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
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
successful completion, unless otherwise noted in the preceding routine
descriptions.
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 initialized. 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 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 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 keycodes are generated and (depending on
previous loads of terminal descriptions) may differ from one execution 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 definitions in the order defined
by the array of string capability names. The last key to be loaded determines
the keycode which will be returned. In ncurses, you may also have extended
capabilities interpreted 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¶
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 recommended.
SEE ALSO¶
ncurses(3NCURSES),
getch(3NCURSES),
initscr(3NCURSES),
util(3NCURSES),
define_key(3NCURSES),
termios(3)