inopts(3NCURSES) Library calls inopts(3NCURSES)
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 /* ignored */, bool bf);
int keypad(WINDOW * win, bool bf);
int meta(WINDOW * win /* ignored */, bool bf);
int nodelay(WINDOW * win, bool bf);
int notimeout(WINDOW * win, bool bf);
int nl(void);
int nonl(void);
void qiflush(void);
void noqiflush(void);
int raw(void);
int noraw(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
curses offers configurable parameters permitting an application to con-
trol the handling of input from the terminal. Some, such as those af-
fecting the terminal's mode or line discipline, are global, applying to
all windows; others apply only to a specific window. The library does
not automatically apply such parameters to new or derived windows; an
application must configure each window for the desired behavior.
Some descriptions below make reference to an input character reading
function: this is wgetch(3NCURSES) in the non-wide character curses API
and wget_wch(3NCURSES) in the wide character API. In addition to the
variant forms of these described in ncurses(3NCURSES), the curses func-
tions wgetstr(3NCURSES) and wget_wstr(3NCURSES) and their own variants
call the appropriate input character reading function.
cbreak, nocbreak
Normally, the terminal driver buffers typed characters, not delivering
them to an application until a line feed or carriage return is typed.
This canonical (“cooked”) line discipline also supports software flow
control, simple line editing functions (character and word erase, and
whole-line erasure or “kill”), and job control. cbreak configures the
terminal in cbreak mode, which disables line buffering and erase and
kill character processing — the interrupt, quit, suspend, and flow con-
trol characters are unaffected — and makes characters typed by the user
immediately available to the program. nocbreak restores canonical
(“cooked”) mode.
The state of the terminal is unknown to a curses application when it
starts; therefore, a program should call cbreak or nocbreak explicitly.
Most interactive programs using curses set cbreak mode. Calling cbreak
overrides raw. The man page for the input character reading function
discusses how cbreak and nocbreak interact with echo and noecho.
echo, noecho
echo and noecho determine whether characters typed by the user are writ-
ten to the curses window by the input character reading function as they
are typed. curses always disables the terminal driver's own echoing.
By default, a curses screen's echo option is set. Authors of most in-
teractive programs prefer to do their own echoing in a controlled area
of the screen, or not to echo at all, so they call noecho. The man page
for the input character reading function discusses how echo and noecho
interact with cbreak and nocbreak.
halfdelay
halfdelay configures half-delay mode, which is similar to cbreak mode in
that characters typed by the user are immediately available to the pro-
gram. However, after blocking for tenths tenth-seconds, an input char-
acter reading function returns ERR if no input is pending. The value of
tenths must be between 1 and 255. Use nocbreak to leave half-delay
mode.
intrflush
intrflush calls qiflush (see below) if bf is TRUE, and noqiflush if bf
is FALSE. It ignores its win argument.
keypad
keypad enables recognition of a terminal's function keys. If enabled
(bf is TRUE), the input character reading function returns a value rep-
resenting the function key, such as KEY_LEFT. (Wide-character API
users: wget_wch(3NCURSES) returns KEY_CODE_YES to indicate the avail-
ability of a function key code in its wch parameter.) If disabled (bf
is FALSE), curses does not treat function keys specially and the program
has to interpret escape sequences itself. If the terminal's keypad can
be turned on (made to transmit) and off (made to work locally), keypad
configures it consistently with the bf parameter. By default, a win-
dow's keypad mode is off.
meta
Initially, whether the terminal returns 7- or 8-bit character codes on
input depends on the configuration of the terminal driver; on POSIX sys-
tems, see termios(3). To force 8 bits to be returned, call meta(...,
TRUE); this is equivalent, on POSIX systems, to setting the CS8 flag on
the terminal. To force 7 bits to be returned, call meta(..., FALSE);
this is equivalent, on POSIX systems, to setting the CS7 flag on the
terminal. curses ignores the window argument win. If the terminfo
string capabilities meta_on (smm) and meta_off (rmm) are defined for the
terminal type, enabling meta mode sends smm to the terminal and dis-
abling it sends rmm to the terminal.
nl, nonl
Initially, whether the terminal reports a carriage return using the
character code for a line feed in cbreak or raw modes depends on the
configuration of the terminal driver; see termios(3). nl configures the
terminal to perform this translation. nonl disables it. Under its
canonical (“cooked”) line discipline, the terminal driver always trans-
lates carriage returns to line feeds.
nodelay
nodelay configures the input character reading function to be non-block-
ing for window win. If no input is ready, the reading function returns
ERR. If disabled (bf is FALSE), the reading function does not return
until it has input.
notimeout
When the input character reading function reads an ESC character, it
sets a timer while waiting for the next character. notimeout(win, TRUE)
disables this timer. The purpose of the timeout is to distinguish se-
quences produced by a function key from those typed by a user. To con-
figure the timeout rather than disabling it, see wtimeout below.
qiflush, noqiflush
qiflush and noqiflush configure the terminal driver's treatment of its
input and output queues when it handles the interrupt, suspend, or quit
characters under the canonical (“cooked”) or cbreak line disciplines on
POSIX systems; see termios(3). The default behavior is inherited from
the terminal driver settings. Calling qiflush configures the terminal
to flush the queues (discarding their contents) when any of these events
occurs, giving the impression of faster response to user input, but mak-
ing the library's model of the screen contents incorrect. Calling
noqiflush prevents such flushing, but might frustrate impatient users on
slow connections if a curses update of the screen is in progress when
the event occurs; see typeahead below for a mitigation of this problem.
You may want to call noqiflush in a signal handler if, after the handler
exits, you want output to continue as though the interrupt had not oc-
curred.
raw, noraw
raw configures the terminal to read input in raw mode, which is similar
to cbreak mode (see cbreak above) except that it furthermore passes
through the terminal's configured interrupt, quit, suspend, and flow
control characters uninterpreted to the application, instead of generat-
ing a signal or acting on I/O flow. The behavior of the terminal's
“Break” key (if any) depends on terminal driver configuration parameters
that curses does not handle. noraw restores the terminal's canonical
(“cooked”) line discipline.
timeout, wtimeout
wtimeout configures whether a curses input character reading function
called on window win uses blocking or non-blocking reads. If delay is
negative, curses uses a blocking read, waiting indefinitely for input.
If delay is zero, the read is non-blocking; an input character reading
function returns ERR if no input is pending. If delay is positive, an
input character reading function blocks for delay milliseconds, and re-
turns ERR if the delay elapses and there is still no input pending.
timeout calls wtimeout on stdscr.
typeahead
Normally, a curses library checks the terminal for input while updating
the screen. If any is found, the update is postponed until the next
wrefresh(3NCURSES) or doupdate(3NCURSES) call, allowing faster response
to user key strokes. The library tests the file descriptor correspond-
ing to the FILE stream pointer passed to newterm(3NCURSES) (or stdin if
initscr(3NCURSES) was called), for pending input. typeahead instructs
curses to test file descriptor fd instead. An fd of -1 disables the
check.
RETURN VALUE
timeout and wtimeout return no value.
cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta,
nodelay, notimeout, nl, nonl, raw, noraw, and typeahead return OK on
success and ERR on failure.
In ncurses, the functions in the previous paragraph return ERR if
• the library's TERMINAL structure for the device has not been ini-
tialized with initscr(3NCURSES), newterm(3NCURSES), or
setupterm(3NCURSES), or
• win is a null pointer (except with intrflush and meta, which ignore
its value).
Further, halfdelay returns ERR if delay is outside the range 1..255.
See section “EXTENSIONS” below for the return values of is_cbreak,
is_echo, is_nl, and is_raw.
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 the terminal's canonical (“cooked”) line discipline from raw and
cbreak, respectively. Mixing raw/noraw calls with cbreak/nocbreak calls
leads to terminal driver control states that are hard to predict or un-
derstand; doing so is not recommended.
EXTENSIONS
ncurses provides four “is_” functions corresponding to cbreak, echo, nl,
and raw, permitting their states to be queried by the application.
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 option is set,
0 if the option is unset, or
-1 if the library's TERMINAL structure for the device has not been
initialized.
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 de-
scribes these functions. It specifies no error conditions for them.
SVr4 describes a successful return value only as “an integer value other
than ERR”.
ncurses follows X/Open Curses and the historical practice of System V
curses, clearing the terminal driver's “echo” flag when initializing the
screen. BSD curses did not, but its raw function turned it off as a
side effect. For best portability, call echo or noecho explicitly just
after initialization, even if your program retains the terminal's canon-
ical (“cooked”) line discipline.
X/Open Curses is ambiguous regarding whether raw should disable the car-
riage return and line feed translation feature controlled by nl and
nonl. BSD curses did turn off these translations; System V curses did
not. ncurses does so, on the assumption that a programmer requesting
raw input wants a clean (ideally, 8-bit clean) connection that the oper-
ating system will not alter.
When keypad is first enabled, ncurses loads the key definitions for the
current terminal description. If the terminal description includes ex-
tended string capabilities, for example, by using the -x option of
tic(1), then ncurses also defines keys for the capabilities whose names
begin with “k”. Corresponding key codes are generated and (depending on
previous loads of terminal descriptions) may differ from one execution
of a program to the next. The generated key codes are recognized by
keyname(3NCURSES), which then returns 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(3NCURSES) to bind a
specific key to a string of the programmer's choice. This feature en-
ables an application to check for its presence with tigetstr(3NCURSES),
and reassign the key code to match its own needs.
Low-level applications can use tigetstr(3NCURSES) to obtain the defini-
tion of any string capability. curses applications use the input char-
acter reading function to obtain key codes from input and rely upon the
order in which the string capabilities are loaded. Multiple key capa-
bility strings can have the same value, but the input character reading
function can report only one key code. Most curses implementations (in-
cluding ncurses) load key definitions in the order they appear in the
strfnames array of string capability names; see
terminfo_variables(3NCURSES). The last capability read using a particu-
lar definition determines the key code to be reported. In ncurses, ex-
tended capabilities can be 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 library uses the later
definition.
HISTORY
4BSD (1980) introduced echo, noecho, nl, nonl, raw, and noraw.
SVr2 (1984) featured a new terminal driver, extending the curses API to
support it with cbreak, nocbreak, intrflush, keypad, meta, nodelay, and
typeahead.
SVr3 (1987) added halfdelay, notimeout, and wtimeout. qiflush and
noqiflush appeared in SVr3.1 (1987), at which point intrflush became a
wrapper for either of these functions, depending on the value of its
Boolean argument. SVr3.1 also added timeout.
ncurses 6.5 (2024) introduced is_cbreak, is_echo, is_nl, and is_raw.
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 con-
version interferes with output optimization, ncurses 6.2 (2020) amended
nl and nonl to eliminate their effect on output.
SEE ALSO
ncurses(3NCURSES), getch(3NCURSES), initscr(3NCURSES), util(3NCURSES),
define_key(3NCURSES), termios(3), terminfo_variables(3NCURSES)
ncurses 6.5 2025-02-01 inopts(3NCURSES)
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