curs_getch(3x) curs_getch(3x)
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
program waits until the system passes text through to the
program. Depending on the setting of cbreak, this is af-
ter one character (cbreak mode), or after the first new-
line (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:
o 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.
o If the character value is any other KEY_ define, the
user is alerted with a beep call.
o If the character is a carriage-return, and if nl is
enabled, it is translated to a line-feed after echo-
ing.
o 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 to-
ken for that function key is returned instead of the raw
characters:
o The predefined function keys are listed in <curses.h>
as macros with values outside the range of 8-bit char-
acters. Their names begin with KEY_.
o Other (user-defined) function keys which may be de-
fined 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 es-
cape 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 es-
cape 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 special keys are defined in <curses.h>.
o Except for the special case KEY_RESIZE, it is neces-
sary to enable keypad for getch to return these codes.
o Not all of these are necessarily supported on any par-
ticular terminal.
o The naming convention may seem obscure, with some ap-
parent 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:
o KEY_RESIZE is returned when the SIGWINCH signal has
been detected (see curs_initscr(3x) and resizeterm(3x)).
This code is returned whether or not keypad has been
enabled.
o 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.
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 de-
fine_key(3x)).
key_defined
checks if there is a key-code defined for a given
string (see key_defined(3x)).
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 move-
ment using wmove, and return an error if the position is
outside the window, or if the window pointer is null.
Use of the escape key by a programmer for a single charac-
ter function is discouraged, as it will cause a delay of
up to one second while the keypad code looks for a follow-
ing function-key sequence.
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 accord-
ing to whether they treat these control keys specially
(and ignore the terminfo), or use the terminfo defini-
tions. 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:
o the terminal description lists the most useful keys,
o the Enter key on the regular keyboard is already han-
dled by the standard ASCII characters for carriage-re-
turn and line-feed,
o 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
o "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 un-
desirable 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.
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 docu-
mentation. This description is adopted from the XSI Curs-
es standard.
The behavior of getch and friends in the presence of han-
dled signals is unspecified in the SVr4 and XSI Curses
documentation. Under historical curses implementations,
it varied depending on whether the operating system's im-
plementation of handled signal receipt interrupts a
read(2) call in progress or not, and also (in some imple-
mentations) depending on whether an input timeout or non-
blocking mode has been set.
KEY_MOUSE is mentioned in XSI Curses, along with a few re-
lated terminfo capabilities, but no higher-level functions
use the feature. The implementation in ncurses is an ex-
tension.
KEY_RESIZE is an extension first implemented for ncurses.
NetBSD curses later added this extension.
Programmers concerned about portability should be prepared
for either of two cases: (a) signal receipt does not in-
terrupt getch; (b) signal receipt interrupts getch and
causes it to return ERR with errno set to EINTR. Under
the ncurses implementation, handled signals never inter-
rupt getch.
The has_key function is unique to ncurses. We recommend
that any code using it be conditionalized on the NCURS-
ES_VERSION feature macro.
curses(3x), curs_inopts(3x), curs_outopts(3x),
curs_mouse(3x), curs_move(3x), curs_refresh(3x), re-
sizeterm(3x).
Comparable functions in the wide-character (ncursesw) li-
brary are described in curs_get_wch(3x).
curs_getch(3x)