Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
curs_getch(3X)							curs_getch(3X)

       getch, wgetch, mvgetch, mvwgetch, ungetch, has_key - get	(or push back)
       characters from curses terminal keyboard

       #include	<curses.h>

       int getch(void);
       int wgetch(WINDOW *win);
       int mvgetch(int y, int x);
       int mvwgetch(WINDOW *win, int y,	int x);
       int ungetch(int ch);
       int has_key(int ch);

   Reading characters
       The getch, wgetch, mvgetch and mvwgetch,	routines read a	character from
       the window.  In no-delay	mode, if no input is waiting, the value	ERR is
       returned.  In delay mode, the program waits  until  the	system	passes
       text  through to	the program.  Depending	on the setting of cbreak, this
       is after	one character  (cbreak	mode),	or  after  the	first  newline
       (nocbreak mode).	 In half-delay mode, the program waits until a charac-
       ter is typed or the specified timeout has been reached.

       If echo is enabled, and the window is not a  pad,  then	the  character
       will also be echoed into	the designated window according	to the follow-
       ing rules:

       o   If the character is the current erase  character,  left  arrow,  or
	   backspace,  the  cursor  is	moved  one  space to the left and that
	   screen position is erased as	if delch had been called.

       o   If the character value is any other KEY_ define, the	user is	alert-
	   ed with a beep call.

       o   If  the character is	a carriage-return, and if nl is	enabled, it is
	   translated to a line-feed after echoing.

       o   Otherwise the character is simply output to the screen.

       If the window is	not a pad, and it has been moved or modified since the
       last call to wrefresh, wrefresh will be called before another character
       is read.

   Keypad mode
       If keypad is TRUE, and a	function key is	pressed, the  token  for  that
       function	key is returned	instead	of the raw characters:

       o   The	predefined  function  keys  are	listed in <curses.h> as	macros
	   with	values outside the range of 8-bit characters.  Their names be-
	   gin with KEY_.

       o   Other  (user-defined)  function keys	which may be defined using de-
	   fine_key(3X)	have no	names, but also	are expected  to  have	values
	   outside the range of	8-bit characters.

       Thus,  a	 variable  intended to hold the	return value of	a function key
       must be of short	size or	larger.

       When a character	that could be the beginning of a function key  is  re-
       ceived  (which, on modern terminals, means an escape character),	curses
       sets a timer.  If the remainder of the sequence does not	come in	within
       the  designated	time,  the character is	passed through;	otherwise, the
       function	key value is returned.	For this reason, many terminals	 expe-
       rience  a  delay	between	the time a user	presses	the escape key and the
       escape is returned to the program.

       In ncurses, the timer normally expires after the	value in ESCDELAY (see
       curs_variables(3X)).   If notimeout is TRUE, the	timer does not expire;
       it is an	infinite (or very large) value.	 Because function keys usually
       begin  with an escape character,	the terminal may appear	to hang	in no-
       timeout mode after  pressing  the  escape  key  until  another  key  is

   Ungetting characters
       The  ungetch routine places ch back onto	the input queue	to be returned
       by the next call	to wgetch.  There is just one input queue for all win-

   Predefined key-codes
       The following special keys are defined in <curses.h>.

       o   Except  for	the special case KEY_RESIZE, it	is necessary to	enable
	   keypad for getch to return these codes.

       o   Not all of these are	necessarily supported on any particular	termi-

       o   The	naming	convention  may	 seem obscure, with some apparent mis-
	   spellings (such as "RSUME" for "resume").  The names	correspond  to
	   the	long  terminfo capability names	for the	keys, and were defined
	   long	ago, in	the 1980s.

		  Name		  Key name
		  KEY_BREAK	  Break	key
		  KEY_DOWN	  The four arrow keys ...
		  KEY_HOME	  Home key (upward+left	arrow)
		  KEY_BACKSPACE	  Backspace
		  KEY_F0	  Function keys; space for 64 keys
				  is reserved.
		  KEY_F(n)	  For 0	<= n <=	63
		  KEY_DL	  Delete line
		  KEY_IL	  Insert line
		  KEY_DC	  Delete character
		  KEY_IC	  Insert char or enter insert mode
		  KEY_EIC	  Exit insert char mode
		  KEY_CLEAR	  Clear	screen
		  KEY_EOS	  Clear	to end of screen
		  KEY_EOL	  Clear	to end of line
		  KEY_SF	  Scroll 1 line	forward
		  KEY_SR	  Scroll 1 line	backward (reverse)
		  KEY_NPAGE	  Next page
		  KEY_PPAGE	  Previous page
		  KEY_STAB	  Set tab
		  KEY_CTAB	  Clear	tab
		  KEY_CATAB	  Clear	all tabs
		  KEY_ENTER	  Enter	or send
		  KEY_SRESET	  Soft (partial) reset
		  KEY_RESET	  Reset	or hard	reset
		  KEY_PRINT	  Print	or copy
		  KEY_LL	  Home down or bottom (lower left)
		  KEY_A1	  Upper	left of	keypad
		  KEY_A3	  Upper	right of keypad

		  KEY_B2	  Center of keypad
		  KEY_C1	  Lower	left of	keypad
		  KEY_C3	  Lower	right of keypad
		  KEY_BTAB	  Back tab key
		  KEY_BEG	  Beg(inning) key
		  KEY_CANCEL	  Cancel key
		  KEY_CLOSE	  Close	key
		  KEY_COMMAND	  Cmd (command)	key
		  KEY_COPY	  Copy key
		  KEY_CREATE	  Create key
		  KEY_END	  End key
		  KEY_EXIT	  Exit key
		  KEY_FIND	  Find key
		  KEY_HELP	  Help key
		  KEY_MARK	  Mark key
		  KEY_MESSAGE	  Message key
		  KEY_MOUSE	  Mouse	event read
		  KEY_MOVE	  Move key
		  KEY_NEXT	  Next object key
		  KEY_OPEN	  Open key
		  KEY_OPTIONS	  Options key
		  KEY_PREVIOUS	  Previous object key
		  KEY_REDO	  Redo key
		  KEY_REFERENCE	  Ref(erence) key
		  KEY_REFRESH	  Refresh key
		  KEY_REPLACE	  Replace key
		  KEY_RESIZE	  Screen resized
		  KEY_RESTART	  Restart key
		  KEY_RESUME	  Resume key
		  KEY_SAVE	  Save key
		  KEY_SBEG	  Shifted beginning key
		  KEY_SCANCEL	  Shifted cancel key
		  KEY_SCOMMAND	  Shifted command key
		  KEY_SCOPY	  Shifted copy key
		  KEY_SCREATE	  Shifted create key
		  KEY_SDC	  Shifted delete char key
		  KEY_SDL	  Shifted delete line key
		  KEY_SELECT	  Select key
		  KEY_SEND	  Shifted end key
		  KEY_SEOL	  Shifted clear	line key
		  KEY_SEXIT	  Shifted exit key
		  KEY_SFIND	  Shifted find key
		  KEY_SHELP	  Shifted help key
		  KEY_SHOME	  Shifted home key
		  KEY_SIC	  Shifted input	key
		  KEY_SLEFT	  Shifted left arrow key
		  KEY_SMESSAGE	  Shifted message key
		  KEY_SMOVE	  Shifted move key
		  KEY_SNEXT	  Shifted next key
		  KEY_SOPTIONS	  Shifted options key
		  KEY_SPREVIOUS	  Shifted prev key
		  KEY_SPRINT	  Shifted print	key
		  KEY_SREDO	  Shifted redo key
		  KEY_SREPLACE	  Shifted replace key
		  KEY_SRIGHT	  Shifted right	arrow
		  KEY_SRSUME	  Shifted resume key
		  KEY_SSAVE	  Shifted save key
		  KEY_SSUSPEND	  Shifted suspend key
		  KEY_SUNDO	  Shifted undo key
		  KEY_SUSPEND	  Suspend key
		  KEY_UNDO	  Undo key

       Keypad is arranged like this:

				| A1  |	 up  |	A3   |
				|left |	 B2  | right |
				| C1  |	down |	C3   |
       A few of	these predefined values	do not correspond to a real key:

       o   KEY_RESIZE  is  returned when the SIGWINCH signal has been detected
	   (see	 initscr(3X)  and  resizeterm(3X)).   This  code  is  returned
	   whether or not keypad has been enabled.

       o   KEY_MOUSE  is returned for mouse-events (see	curs_mouse(3X)).  This
	   code	relies upon whether or not keypad(3X) has  been	 enabled,  be-
	   cause  (e.g., with xterm mouse prototocol) ncurses must read	escape
	   sequences, just like	a function key.

   Testing key-codes
       The has_key routine takes a key-code value from the above list, and re-
       turns TRUE or FALSE according to	whether	the current terminal type rec-
       ognizes a key with that value.

       The library also	supports these extensions:

	       defines a key-code for a	given string (see define_key(3X)).

	       checks if there is a key-code defined for a given  string  (see

       All  routines  return the integer ERR upon failure and an integer value
       other than ERR (OK in the case of ungetch) upon successful completion.

	       returns ERR if there is no more room in the FIFO.

	       returns ERR if the window pointer is null, or  if  its  timeout
	       expires without having any data,	or if the execution was	inter-
	       rupted by a signal (errno will be set to	EINTR).

       Functions with a	"mv" prefix first  perform  a  cursor  movement	 using
       wmove, and return an error if the position is outside the window, or if
       the window pointer is null.

       Use of the escape key by	a programmer for a single  character  function
       is  discouraged,	as it will cause a delay of up to one second while the
       keypad code looks for a following function-key sequence.

       Some keys may be	the same as commonly used control keys,	e.g.,  KEY_EN-
       TER  versus control/M, KEY_BACKSPACE versus control/H.  Some curses im-
       plementations may differ	according to whether they treat	these  control
       keys  specially	(and ignore the	terminfo), or use the terminfo defini-
       tions.  Ncurses uses the	terminfo definition.  If it says that  KEY_EN-
       TER is control/M, getch will return KEY_ENTER when you press control/M.

       Generally,  KEY_ENTER denotes the character(s) sent by the Enter	key on
       the numeric keypad:

       o   the terminal	description lists the most useful keys,

       o   the Enter key on the	regular	keyboard is  already  handled  by  the
	   standard ASCII characters for carriage-return and line-feed,

       o   depending on	whether	nl or nonl was called, pressing	"Enter"	on the
	   regular keyboard may	return either a	carriage-return	or  line-feed,
	   and finally

       o   "Enter or send" is the standard description for this	key.

       When   using   getch,  wgetch,  mvgetch,	 or  mvwgetch,	nocbreak  mode
       (nocbreak) and echo mode	(echo) should not be used at  the  same	 time.
       Depending  on the state of the tty driver when each character is	typed,
       the program may produce undesirable results.

       Note that getch,	mvgetch, and mvwgetch may be macros.

       Historically, the set of	keypad macros was largely defined by  the  ex-
       tremely	function-key-rich  keyboard of the AT&T	7300, aka 3B1, aka Sa-
       fari 4.	Modern personal	computers usually have only a small subset  of
       these.	IBM  PC-style  consoles	 typically  support  little  more than
       KEY_PPAGE,  and	function  keys	1  through 12.	The Ins	key is usually
       mapped to KEY_IC.

       The *get* functions are described in the	XSI Curses standard, Issue  4.
       They  read  single-byte	characters  only.  The standard	specifies that
       they return ERR on failure, but specifies no error conditions.

       The echo	behavior of these functions on	input  of  KEY_	 or  backspace
       characters  was not specified in	the SVr4 documentation.	 This descrip-
       tion is adopted from the	XSI Curses standard.

       The behavior of getch and friends in the	presence of handled signals is
       unspecified in the SVr4 and XSI Curses documentation.  Under historical
       curses implementations, it varied depending on  whether	the  operating
       system's	 implementation	of handled signal receipt interrupts a read(2)
       call in progress	or not,	and also (in some  implementations)  depending
       on whether an input timeout or non-blocking mode	has been set.

       KEY_MOUSE is mentioned in XSI Curses, along with	a few related terminfo
       capabilities, but no higher-level functions use the feature.   The  im-
       plementation in ncurses is an extension.

       KEY_RESIZE is an	extension first	implemented for	ncurses.  NetBSD curs-
       es later	added this extension.

       Programmers concerned about portability should be prepared  for	either
       of  two	cases: (a) signal receipt does not interrupt getch; (b)	signal
       receipt interrupts getch	and causes it to return	ERR with errno set  to

       The  has_key function is	unique to ncurses.  We recommend that any code
       using it	be conditionalized on the NCURSES_VERSION feature macro.

       curses(3X),    curs_inopts(3X),	  curs_outopts(3X),    curs_mouse(3X),
       curs_move(3X), curs_refresh(3X),	curs_variables(3X), resizeterm(3X).

       Comparable  functions  in the wide-character (ncursesw) library are de-
       scribed in curs_get_wch(3X).



Want to link to this manual page? Use this URL:

home | help