# curs_getch 3x

    curs_getch(3x)                                           curs_getch(3x)

## NAME

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

## SYNOPSIS

           #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);

## DESCRIPTION

### 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-
               ing.

           o   Otherwise  the  character  is  simply  output  to  the
               screen.

           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
           characters:

           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
               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  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
               1980s.

                Name            Key name
                -------------------------------------------------
                KEY_BREAK       Break key
                KEY_DOWN        The four arrow keys ...
                KEY_UP
                KEY_LEFT
                KEY_RIGHT
                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  curs_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, 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:

              define_key
                   defines  a  key-code  for  a given string (see de-
                   fine_key(3x)).

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

## RETURN VALUE

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

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

              wgetch
                   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  move-
           ment  using  wmove, and return an error if the position is
           outside the window, or if the window pointer is null.

## NOTES

           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
               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 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_DOWN,    KEY_LEFT,   KEY_RIGHT,   KEY_HOME,   KEY_END,
           KEY_NPAGE, KEY_PPAGE, and function keys 1 through 12.  The
           Ins key is usually mapped to KEY_IC.

## PORTABILITY

           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-
           tension.

           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.  Under
           the ncurses implementation, handled signals  never  inter-
           rupt getch.

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

## SEE ALSO

           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).

                                                             curs_getch(3x)