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:
• 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.
• If the character is a carriage-return, and if nl is enabled,
it is translated to a line-feed after echoing.
• 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:
• 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_.
• 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>.
• Except for the special case KEY_RESIZE, it is necessary to
enable keypad for getch to return these codes.
• Not all of these are necessarily supported on any particular
terminal.
• 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 read
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 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
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:
• 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.
• 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 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)).
