# 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);

           /* extension */
           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 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
           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 win-
           dows.

### 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-
               nal.

           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_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 occurred
                      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 insert 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
                      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(1) mouse prototocol) ncurses must read es-
               cape 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:

              define_key
                   defines a key-code for a given string (see define_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, 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.

## NOTES

           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_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 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
           EINTR.

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

## SEE ALSO

           curses(3x), curs_inopts(3x), curs_mouse(3x),  curs_move(3x),  curs_out-
           opts(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).

                                                                    curs_getch(3x)