curs_inopts(3) Library calls curs_inopts(3)
NAME
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
SYNOPSIS
#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);
DESCRIPTION
ncurses provides several functions that 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
desired.
cbreak, nocbreak
Normally, the terminal 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.]
echo, 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
terminal 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.]
halfdelay
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.
intrflush
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
terminal driver queue is 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 terminal driver
settings. The win argument is ignored.
keypad
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.
meta
Initially, whether the terminal returns 7 or 8 significant bits on
input depends on the control mode of the terminal 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.
nl, nonl
The nl and nonl routines control whether the underlying display device
translates the return key into newline on input.
nodelay
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.
notimeout
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
distinguish sequences produced by a function key from those typed by a
user.
raw, noraw
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
terminal driver that are not set by curses.
qiflush, nqiflush
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.
timeout, wtimeout
The timeout and wtimeout routines set blocking or non-blocking read for
a given window. If delay is negative, a blocking read is used (i.e.,
waits indefinitely for input). If delay is zero, then a 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).
typeahead
curses does "line-breakout optimization" by looking for typeahead
periodically while updating the screen. If input is found, and it is
coming from a terminal, 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.
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 Curses does not specify 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.
NOTES
echo, noecho, halfdelay, intrflush, meta, nl, nonl, nodelay, notimeout,
noqiflush, qiflush, timeout, and wtimeout may be implemented as macros.
noraw and nocbreak follow historical practice in that they attempt to
restore normal ("cooked") mode from raw and cbreak modes respectively.
Mixing raw/noraw and cbreak/nocbreak calls leads to terminal driver
control states that are hard to predict or understand; doing so is not
recommended.
EXTENSIONS
ncurses provides four "is_" functions that 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 library is not initialized.
They were designed for ncurses(3X), and are not found in SVr4 curses,
4.4BSD curses, or any other previous curses implementation.
PORTABILITY
Applications employing ncurses extensions should condition their use on
the visibility of the NCURSES_VERSION preprocessor macro.
Except as noted in section "EXTENSIONS" above, X/Open Curses, Issue 4,
Version 2 describes these functions.
ncurses follows X/Open Curses and the historical practice of 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.
X/Open Curses is ambiguous regarding whether raw should disable the
CR/LF translations controlled by nl and nonl. BSD curses did turn off
these translations; AT&T curses (at least as late as SVr1) did not.
ncurses does so, on the assumption 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(3X) 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(3X)
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.
HISTORY
Formerly, ncurses used nl and nonl to control the conversion of
newlines to carriage return/line feed on output as well as input.
X/Open Curses documents the use of these functions only for input.
This difference arose from converting the pcurses source (1986), which
used ioctl(2) calls and the sgttyb structure, to termios (the POSIX
terminal API). In the former, both input and output were controlled
via a single option CRMOD, while the latter separates these features.
Because that conversion interferes with output optimization, ncurses
6.2 (2020) amended nl and nonl to eliminate their effect on output.
SEE ALSO
curses(3X), curs_getch(3X), curs_initscr(3X), curs_util(3X),
define_key(3X), termios(3)
ncurses 6.5 2024-04-13 curs_inopts(3)
ncurses 6.5 - Generated Wed May 1 15:44:14 CDT 2024