curs_getch 3x 2024-02-17 ncurses 6.4 Library calls

curs_getch(3x)                   Library calls                  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
       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

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

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

       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_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:

               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

               o   if the window pointer is null, or

               o   if its timeout expires without having any data, or

               o   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.


       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

       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_PPAGE,  and  function  keys  1  through 12.  The Ins key is usually
       mapped to KEY_IC.


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


       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

       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_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                       2024-02-17                    curs_getch(3x)