curs_getch(3X) curs_getch(3X)
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 charac-
ter 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 charac-
ter is the current erase character, left arrow, or backspace, the cur-
sor 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
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 func-
tion 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 re-
ceived (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 expe-
rience 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 win-
dows.
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 charac-
ter 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_EN-
TER/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/Can-
cel 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/Mes-
sage key KEY_MOUSE/Mouse event read KEY_MOVE/Move key KEY_NEXT/Next ob-
ject key KEY_OPEN/Open key KEY_OPTIONS/Options key KEY_PREVIOUS/Previ-
ous object key KEY_REDO/Redo key KEY_REFERENCE/Ref(erence) key KEY_RE-
FRESH/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_SCOM-
MAND/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_SOP-
TIONS/Shifted options key KEY_SPREVIOUS/Shifted prev key
KEY_SPRINT/Shifted print key KEY_SREDO/Shifted redo key KEY_SRE-
PLACE/Shifted replace key KEY_SRIGHT/Shifted right arrow KEY_SR-
SUME/Shifted resume key KEY_SSAVE/Shifted save key KEY_SSUSPEND/Shifted
suspend key KEY_SUNDO/Shifted undo key KEY_SUSPEND/Suspend key KEY_UN-
DO/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 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.
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 comple-
tion.
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.
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 con-
trol/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 ex-
tremely function-key-rich keyboard of the AT&T 7300, aka 3B1, aka Sa-
fari 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 descrip-
tion 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 inter-
rupt 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
curses(3X), curs_inopts(3X), curs_mouse(3X), curs_move(3X), curs_re-
fresh(3X), resizeterm(3X).
Comparable functions in the wide-character (ncursesw) library are de-
scribed in curs_get_wch(3X).
curs_getch(3X)