curs_getch 3x

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  af-
       ter  one  character (cbreak mode), or after the first new-
       line (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:

       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 alerted 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 echo-

       o   Otherwise  the  character  is  simply  output  to  the

       If the window is not a pad, and it has been moved or modi-
       fied 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 to-
       ken for that function key is returned instead of  the  raw

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

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

       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  es-
       cape 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 es-
       cape 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 pressed.

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 windows.

Predefined key-codes

       The following special keys are defined in <curses.h>.

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

       o   Not all of these are necessarily supported on any par-
           ticular terminal.

       o   The naming convention may seem obscure, with some  ap-
           parent  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

            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

       o   KEY_MOUSE    is   returned   for   mouse-events   (see
           curs_mouse(3x)).  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 de-

               checks if there is a key-code defined for a  given
               string (see key_defined(3x)).


       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 interrupted by a signal (errno
               will be set to EINTR).

       Functions with a "mv" prefix first perform a cursor  move-
       ment  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 charac-
       ter  function  is discouraged, as it will cause a delay of
       up to one second while the keypad code looks for a follow-
       ing 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 accord-
       ing 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_ENTER  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 han-
           dled by the standard ASCII characters for carriage-re-
           turn 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

       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 un-
       desirable 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_UP,
       KEY_NPAGE, 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 stan-
       dard, 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 docu-
       mentation.  This description is adopted from the XSI Curs-
       es standard.

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

       KEY_MOUSE is mentioned in XSI Curses, along with a few re-
       lated terminfo capabilities, but no higher-level functions
       use the feature.  The implementation in ncurses is an  ex-

       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 in-
       terrupt getch; (b) signal  receipt  interrupts  getch  and
       causes it to return ERR with errno set to EINTR.

       The  has_key  function is unique to ncurses.  We recommend
       that any code using it be conditionalized  on  the  NCURS-
       ES_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) li-
       brary are described in curs_get_wch(3x).