has_key – get (or push back) characters from curses terminal keyboard
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.
Unless 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
If keypad is TRUE, and a function key is pressed, the token for
that function key is returned instead of the raw characters.
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
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.
There is just one input queue for all windows.
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.
|KEY_DOWN||The four arrow keys …|
|KEY_HOME||Home key (upward+left arrow)|
Function keys; space for 64 keys is reserved.
For 0 ≤ n ≤ 63
|KEY_IC||Insert char or enter insert mode|
|KEY_EIC||Exit insert char mode|
|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_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_COMMAND||Cmd (command) key|
|KEY_MOUSE||Mouse event read|
|KEY_NEXT||Next object key|
|KEY_PREVIOUS||Previous object 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_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|
Keypad is arranged like this:
The has_key routine takes a key value from the above list, and
returns TRUE or FALSE according to whether
the current terminal type recognizes a key with that value.
Note that a few values do not correspond to a real key,
e.g., KEY_RESIZE and KEY_MOUSE.
See resizeterm(3X) for more details about KEY_RESIZE, and
curs_mouse(3X) for a discussion of KEY_MOUSE.
All routines return the integer ERR upon failure and an integer value
other than ERR (OK in the case of ungetch()) upon successful
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.
Note that 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.
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.
personal computers usually have only a small subset of these.
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.
The *get* functions are described in the XSI Curses standard, Issue 4.
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.
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
Under the ncurses implementation, handled signals never
Comparable functions in the wide-character (ncursesw) library are