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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | NOTES | SEE ALSO | COLOPHON |
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curs_inopts(3X) curs_inopts(3X)
cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad,
meta, nl, nonl, nodelay, notimeout, raw, noraw, qiflush,
noqiflush, timeout, wtimeout, typeahead - curses 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);
The ncurses library provides several functions which let an ap‐
plication 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.
cbreak/nocbreak
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 rou‐
tine 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 tty driver is always disabled, but initially getch is in echo
mode, so characters typed are echoed. Authors of most interac‐
tive 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 simi‐
lar to cbreak mode in that characters typed by the user are imme‐
diately 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 out‐
put 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 inher‐
ited from the tty driver settings. The window argument is ig‐
nored.
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 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 ter‐
minal 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 differentiate between sequences received from a
function key and 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 tty driver that are not set by curs‐
es.
qiflush/noqiflush
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, af‐
ter the handler exits.
timeout/wtimeout
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 in‐
put is waiting). If delay is positive, then read blocks for de‐
lay 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
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 check‐
ing. 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 implementa‐
tion, functions with a window parameter will return an error if
it is null. Any function will also return an error if the termi‐
nal was not initialized. Also,
halfdelay
returns an error if its parameter is outside the
range 1..255.
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 curs‐
es differed from this slightly; it left the echo bit on at ini‐
tialization, 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 (ide‐
ally 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 descrip‐
tion includes extended string capabilities, e.g., from using the
-x option of @TIC@, then ncurses also defines keys for the capa‐
bilities whose names begin with “k”. The corresponding keycodes
are generated and (depending on previous loads of terminal de‐
scriptions) may differ from one execution of a program to the
next. The generated keycodes are recognized by the keyname func‐
tion (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 capabili‐
ty'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 key‐
codes 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 defini‐
tions. These are loaded after the predefined keys, and if a ca‐
pability's value is the same as a previously-loaded key defini‐
tion, 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), de‐
fine_key(3X), termios(3)
This page is part of the ncurses (new curses) project. Informa‐
tion about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
curs_inopts(3X)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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