curs_inopts(3x) Library calls curs_inopts(3x)
cbreak, echo, halfdelay, intrflush, is_cbreak, is_echo, is_nl, is_raw,
keypad, meta, nl, nocbreak, nodelay, noecho, nonl, noqiflush, noraw,
notimeout, qiflush, raw, timeout, wtimeout, typeahead - get and set
curses terminal input options
#include <curses.h>
int cbreak(void);
int nocbreak(void);
int echo(void);
int noecho(void);
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);
int nl(void);
int nonl(void);
int raw(void);
int noraw(void);
void qiflush(void);
void noqiflush(void);
int halfdelay(int tenths);
void timeout(int delay);
void wtimeout(WINDOW *win, int delay);
int typeahead(int fd);
/* extensions */
int is_cbreak(void);
int is_echo(void);
int is_nl(void);
int is_raw(void);
The ncurses library provides several functions which let an application
change the way input from the terminal is handled. Some are global,
applying to all windows. Others apply only to a specific window.
Window-specific settings are not automatically applied to new or
derived windows. An application must apply these to each window, if
the same behavior is needed.
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 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(3x) 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), and 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 the option (bf is FALSE) 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(3x) 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(3x) 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(3)].
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 nl and nonl routines control whether the underlying display device
translates the return key into newline on input.
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.
When interpreting an escape sequence, wgetch(3x) 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 termios(3)]. 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(3x) 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 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.
This implementation provides four functions which may be used to detect
if the corresponding flags were set or reset:
Query Set Reset
------------------------------
is_cbreak cbreak nocbreak
is_echo echo noecho
is_nl nl nonl
is_raw raw noraw
In each case, the function returns
1 if the flag is set,
0 if the flag is reset, or
-1 if the curses library was not initialized.
These routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that any
code depending on ncurses extensions be conditioned using
NCURSES_VERSION.
Except as noted in the section on extensions, 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.
The XSI Curses standard is ambiguous on the question of whether raw
should disable the CRLF translations controlled by nl and nonl. BSD
curses did turn off these translations; AT&T curses (at least as late
as SVr1) did not. We chose to do so, on the theory that a programmer
requesting raw input wants a clean (ideally 8-bit clean) connection
that the operating system will not alter.
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.
Note that echo, noecho, halfdelay, intrflush, meta, nl, nonl, 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.
curses(3x), curs_getch(3x), curs_initscr(3x), curs_util(3x),
define_key(3x), termios(3)
ncurses 6.4 2023-09-16 curs_inopts(3x)