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curs_getch(3)                                                    curs_getch(3)




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.


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 description
       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
       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).



                                                                  curs_getch(3)

ncurses 6.4 - Generated Tue Jan 3 13:43:53 CST 2023
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