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);

       /* extension */
       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 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

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-

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-

       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_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:

               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 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 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.


       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_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 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

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


       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).