# curs_getch 3x 2023-12-23 ncurses 6.4 Library calls

    curs_getch(3x)                   Library calls                  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
           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 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
               begin with KEY_.

           o   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
           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 necessary to enable
               keypad for getch to return these codes.

           o   Not all of  these  are  necessarily  supported  on  any  particular
               terminal.

           o   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_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,
               because  (e.g.,  with  xterm(1) 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 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
                   interrupted 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_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
           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
           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.

## EXTENSIONS

           has_key  was designed for ncurses(3x), and is not found in SVr4 curses,
           4.4BSD curses, or any other previous curses implementation.

## PORTABILITY

           Applications employing ncurses extensions should condition their use on
           the visibility of the NCURSES_VERSION preprocessor macro.

           X/Open  Curses,  Issue  4, Version 2, describes getch, wgetch, mvgetch,
           mvwgetch, and ungetch.  They read  single-byte  characters  only.   The
           standard  specifies  that  they return ERR on failure, but describes no
           failure conditions.

           The echo behavior of these functions on  input  of  KEY_  or  backspace
           characters   was   not  specified  in  the  SVr4  documentation.   This
           description is adapted from X/Open Curses.

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

           KEY_MOUSE is mentioned in X/Open Curses, along with a few related term-
           info 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.

           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_outopts(3x), curs_refresh(3x), curs_variables(3x), resizeterm(3x)

           Comparable  functions  in  the  wide-character  (ncursesw)  library are
           described in curs_get_wch(3x).

    ncurses 6.4                       2023-12-23                    curs_getch(3x)