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);
int has_key(int ch);
DESCRIPTION¶
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.
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. There is 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) |
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 |
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(3NCURSES) for
more details about
KEY_RESIZE, and
mouse(3NCURSES) for a
discussion of
KEY_MOUSE.
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.
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.
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.
Generally,
KEY_ENTER denotes the character(s) sent by the
Enter
key on the numeric keypad:
- •
- the terminal description lists the most useful keys,
- •
- the Enter key on the regular keyboard is already handled by the
standard ASCII characters for carriage-return and line-feed,
- •
- 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
- •
- "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.
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_VERSION feature macro.
SEE ALSO¶
ncurses(3NCURSES),
inopts(3NCURSES),
outopts(3NCURSES),
mouse(3NCURSES),
move(3NCURSES),
refresh(3NCURSES),
resizeterm(3NCURSES).
Comparable functions in the wide-character (ncursesw) library are described in
get_wch(3NCURSES).