getch, wgetch, mvgetch, mvwgetch, ungetch - 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 new-
line (nocbreak mode). In half-delay mode, the program
waits until a character is typed or the specified timeout
has been reached.
If noecho has been set, then the character will also be
echoed into the designated window according to the follow-
ing rules: If the character is the current erase charac-
ter, 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
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
The ungetch routine places ch back onto the input queue to
be returned by the next call to wgetch. Note that there
is, in effect, 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.
center tab(/) ; l l l l . 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/T{ Function keys;
space for 64 keys is reserved. T} KEY_F(n)/T{ For 0 <= n
<= 63 T} 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_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_RESTART/Restart key KEY_RESUME/Resume key
KEY_SAVE/Save key KEY_SBEG/Shifted beginning key KEY_SCAN-
CEL/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 mes-
sage key KEY_SMOVE/Shifted move key KEY_SNEXT/Shifted next
key KEY_SOPTIONS/Shifted options key KEY_SPREVIOUS/Shifted
KEY_SRIGHT/Shifted right arrow KEY_SRSUME/Shifted resume
key KEY_SSAVE/Shifted save key KEY_SSUSPEND/Shifted sus-
pend key KEY_SUNDO/Shifted undo key KEY_SUSPEND/Suspend
key KEY_UNDO/Undo key
Keypad is arranged like this:
center allbox tab(/) ; c c c . 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 as the current termi-
nal type recognizes a key with that value.
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.
NOTES
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.
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 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
dled 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 imple-
mentations) depending on whether an input timeout or non-
blocking mode hsd 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 inter-
rupt getch.
The has_key function is unique to ncurses. We recommend
that any code using it be conditionalized on the NCURSES
feature macro.
SEE ALSO
curses(3X), curs_inopts(3X), curs_move(3X),
curs_refresh(3X).