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
   character 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
   following rules:

   *   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.

   *   If the character value is  any  other  KEY_  define,  the  user  is
       alerted with a beep call.

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

   *   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:

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

   *   Other  (user-defined)  function  keys  which  may  be defined using
       define_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
   received  (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
   experience  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
   notimeout 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

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

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

   *   Not all of  these  are  necessarily  supported  on  any  particular

   *   The   naming  convention  may  seem  obscure,  with  some  apparent
       misspellings (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:

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

   *   KEY_MOUSE is returned for mouse-events (see mouse(3NCURSES)).  This
       code relies upon  whether  or  not  keypad(3X)  has  been  enabled,
       because  (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
   returns  TRUE  or  FALSE according to whether the current terminal type
   recognizes 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

           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.

   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_ENTER  versus  control/M,  KEY_BACKSPACE  versus  control/H.   Some
   curses implementations may differ according to whether they treat these
   control  keys  specially (and ignore the terminfo), or use the terminfo
   definitions.  Ncurses uses the terminfo definition.  If  it  says  that
   KEY_ENTER  is  control/M,  getch  will  return KEY_ENTER when you press

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

   *   the terminal description lists the most useful keys,

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

   *   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

   *   "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
   extremely function-key-rich keyboard of the AT&T  7300,  aka  3B1,  aka
   Safari  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
   description 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
   implementation in ncurses is an extension.

   KEY_RESIZE is an  extension  first  implemented  for  ncurses.   NetBSD
   curses 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
   EINTR.   Under  the  ncurses  implementation,  handled  signals   never
   interrupt getch.

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


   ncurses(3NCURSES),         inopts(3NCURSES),         outopts(3NCURSES),
   mouse(3NCURSES),           move(3NCURSES),           refresh(3NCURSES),
   curses_variables(3NCURSES), resizeterm(3NCURSES).

   Comparable functions  in  the  wide-character  (ncursesw)  library  are
   described in get_wch(3NCURSES).



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