curs_getch(3) UNIX Programmer's Manual curs_getch(3)
getch, wgetch, mvgetch, mvwgetch, ungetch, has_key - get (or
push back) characters from curses terminal keyboard
#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 pro-
gram waits until the system passes text through to the pro-
gram. Depending on the setting of cbreak, this is after one
character (cbreak mode), or after the first newline (noc-
break 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 modi-
fied 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 charac-
ters. 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 se-
quence 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 experi-
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curs_getch(3) UNIX Programmer's Manual curs_getch(3)
ence 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
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curs_getch(3) UNIX Programmer's Manual curs_getch(3)
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
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curs_getch(3) UNIX Programmer's Manual curs_getch(3)
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(3) for more details about
KEY_RESIZE, and curs_mouse(3) for a discussion of KEY_MOUSE.
All routines return the integer ERR upon failure and an in-
teger value other than ERR (OK in the case of ungetch())
upon successful completion.
ungetch
returns an error if there is no more room in the
FIFO.
wgetch
returns an error if the window pointer is null, or
if its timeout expires without having any data.
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 ig-
nore 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
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curs_getch(3) UNIX Programmer's Manual curs_getch(3)
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 usu-
ally have only a small subset of these. IBM PC-style con-
soles 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 stan-
dard, 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 documen-
tation. 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 documenta-
tion. Under historical curses implementations, it varied
depending on whether the operating system's implementation
of handled signal receipt interrupts a read(2) call in pro-
gress 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 inter-
rupt 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.
curses(3), curs_inopts(3), curs_mouse(3), curs_move(3),
curs_refresh(3), resizeterm(3).
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