getch(), mvgetch(), mvwgetch(), ungetch(), wgetch() -- 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);

int has_key(int ch);

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 noecho() has been set, then the character will also be echoed into the designated window according to the following rules: 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. If the character value is any other KEY_ define, the user is alerted with a beep() call. 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.

If keypad() is TRUE, and a function key is pressed, the token for that function key is returned instead of the raw characters. Possible function keys are defined in <curses.h> as macros with values outside the range of 8-bit characters whose names begin with KEY_. 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.

The ungetch() routine places ch back onto the input queue to be returned by the next call to wgetch(). Note that there is, in effect, just one input queue for all windows.

Function Keys

The following function keys, defined in <curses.h>, might be returned by getch() if keypad() has been enabled. Note that not all of these are necessarily supported on any particular terminal.

       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).  Keypad is
                            arranged like this:
                                 A1       up       A3
                                 left     B2       right
                                 C1       down     C3
       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_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_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 input 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_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

The has_key() routine takes a key value from the above list, and returns TRUE or FALSE according as the current terminal type recognizes a key with that value.

RETURN VALUES

All routines return the integer ERR upon failure and an integer value other than ERR (OK in the case of ungetch()) upon successful completion.

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.

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 chars 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() call in progress or not, and also (in some implementations) depending on whether an input timeout or nonblocking mode hsd been set. 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. Under the ncurses implementation, handled signals never interrupt getch().

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

AVAILABILITY

MKS Toolkit for Professional Developers
MKS Toolkit for Enterprise Developers
MKS Toolkit for Enterprise Developers 64-Bit Edition

getch(), mvgetch(), mvwgetch(), ungetch(), wgetch()
get (or push back) characters from curses terminal keyboard

Curses Function