Ubuntu Manpage: cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta, nl, nonl, nodelay,

Provided by: ncurses-doc_6.4+20230625-2_all

NAME

       cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta, nl, nonl, nodelay,
       notimeout, raw, noraw, qiflush, noqiflush, timeout, wtimeout, typeahead - curses 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);

DESCRIPTION

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.

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 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.]

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 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.]

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 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.

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 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 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 curses.

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, 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, 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).

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
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.

       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.

NOTES