curs_getch(3X) Library calls curs_getch(3X)
NAME
getch, wgetch, mvgetch, mvwgetch, ungetch, has_key - get (or push back)
characters from curses terminal keyboard buffer
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 c);
/* extension */
int has_key(int c);
DESCRIPTION
Reading Characters
wgetch gathers a key event from the terminal keyboard associated with a
curses window win. ncurses(3X) describes the variants of this function.
When input is pending, wgetch returns an integer identifying the key
event; for alphanumeric and punctuation keys, the space bar, and
(usually) the Backspace, Tab, Return, and Escape keys, this value
corresponds to the character encoding used by the terminal. Use of the
control key as a modifier, by holding it down while pressing and
releasing another key, often results in a distinct code. The behavior of
other keys depends on whether win is in keypad mode; see subsection
"Keypad Mode" below.
If no input is pending, then if the no-delay flag is set in the window
(see nodelay(3X)), the function returns ERR; otherwise, curses waits
until the terminal has input. If cbreak(3X) or raw(3X) has been called,
this happens after curses reads one key event. If nocbreak(3X) or
noraw(3X) has been called, it occurs when curses reads a newline.
(Because the terminal's canonical or "cooked" mode is line-buffered,
multiple wgetch calls may then be necessary to empty the input queue.)
If halfdelay(3X) has been called, curses waits until input is available
or the specified delay elapses.
If echo(3X) has been called, and the window is not a pad, curses writes
the returned character c to the window (at the cursor position) per the
following rules.
o If c matches the terminal's erase character (see erasechar(3X)), and
the cursor is not at the window's leftmost column, the cursor moves
leftward one position and the new position is erased as if wmove(3X)
and then wdelch(3X) were called. When the window's keypad mode is
enabled (see below), KEY_LEFT and KEY_BACKSPACE are handled the same
way.
o curses writes any other c to the window, as with wechochar(3X).
o If the window win has been moved or modified since the last call to
wrefresh(3X), curses calls wrefresh on it.
If c is a carriage return and nl(3X) has been called, wgetch returns the
character code for line feed instead.
Keypad Mode
Call keypad(3X) on a window to configure keypad mode when reading input
from it. In keypad mode, curses treats key strokes not from the
alphabetic section of the keyboard (those corresponding to the ECMA-6
character set -- see ascii(7) -- optionally modified by either the
control or shift keys) as function keys. (In curses, the term "function
key" includes but is not limited to keycaps engraved with "F1", "PF1",
and so on.) If a window is in keypad mode, wgetch translates these key
strokes to a numeric code corresponding to the KEY_ symbols listed in
subsection "Key Codes" below. If the window is not in keypad mode, the
input queue populates with the characters of the function key's escape
sequence, which the application must collect individually with multiple
wgetch calls.
o The curses.h header file declares many function keys whose names
begin with KEY_; these object-like macros have integer values outside
the range of eight-bit character codes.
o In ncurses, user-defined function keys are configured with
define_key(3X); they have no names, but are also expected to have
integer values outside the range of eight-bit character codes.
A variable intended to hold a function key code must thus be of type
short or larger.
Most terminals one encounters follow the ECMA-48 standard insofar as
their function keys produce character sequences prefixed with the escape
character ESC. This fact implies that curses cannot distinguish a user's
press of the escape key (assuming it sends ESC) from the beginning of a
function key's character sequence without waiting to see if, and how
soon, further input arrives.
o If the escape sequence matches a string capability defining a
function key for the terminal type (such as key_home (khome) or
key_up (kuu1)), wgetch returns the function key code corresponding to
the unique sequence defined by the terminal.
o If the escape sequence matches no function keys defined for the
terminal type, call wgetch repeatedly to obtain the codes of the
individual characters of the sequence, in the order they occurred in
the input.
o If wgetch cannot decide the validity of the input as a function key
because it has not read enough characters to disambiguate it, the
function waits until it has this information or the escape delay
elapses. Configure the escape delay with the global variable
ESCDELAY, an extension (see section "EXTENSIONS" below), or the
environment variable of the same name (see section "ENVIRONMENT" of
ncurses(3X)), also an extension.
Consequently, a user of a curses application that employs keypad mode may
experience a pause or "hang" after pressing the escape key while curses
collects sufficient characters to disambiguate the input. If the window
is in "no time-out" mode, the escape delay is effectively infinite; see
notimeout(3X). In the event of such a pause, further typing "awakens"
curses.
Ungetting Characters
ungetch places c into the input queue to be returned by the next call to
wgetch. A single input queue serves all windows associated with the
screen.
Key Codes
The header file curses.h defines the following function key codes.
o Except for the special case of KEY_RESIZE, a window's keypad mode
must be enabled for wgetch to read these codes from it.
o Not all of these are necessarily supported on any particular
terminal.
o The naming convention may seem obscure, with some apparent
misspellings (such as "RSUME" for "resume"); the names correspond to
the terminfo capability names for the keys, and were standardized
before the IBM PC/AT keyboard layout achieved a dominant position in
industry.
Symbol Key name
===================================================================
KEY_BREAK Break key
KEY_DOWN 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) Function key n where 0 <= n <= 63
KEY_DL Delete line
KEY_IL Insert line
KEY_DC Delete character
KEY_IC Insert character/Enter insert mode
KEY_EIC Exit insert character mode
KEY_CLEAR Clear screen
KEY_EOS Clear to end of screen
KEY_EOL Clear to end of line
KEY_SF Scroll one line forward
KEY_SR Scroll one line backward (reverse)
KEY_NPAGE Next page/Page up
KEY_PPAGE Previous page/Page down
KEY_STAB Set tab
KEY_CTAB Clear tab
KEY_CATAB Clear all tabs
KEY_ENTER Enter/Send
KEY_SRESET Soft (partial) reset
KEY_RESET (Hard) reset
KEY_PRINT Print/Copy
KEY_LL Home down/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 occurred
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_SELECT Select key
KEY_SUSPEND Suspend key
KEY_UNDO Undo 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 character key
KEY_SDL Shifted delete line 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 insert key
KEY_SLEFT Shifted left arrow key
KEY_SMESSAGE Shifted message key
KEY_SMOVE Shifted move key
KEY_SNEXT Shifted next object key
KEY_SOPTIONS Shifted options key
KEY_SPREVIOUS Shifted previous object key
KEY_SPRINT Shifted print key
KEY_SREDO Shifted redo key
KEY_SREPLACE Shifted replace key
KEY_SRIGHT Shifted right arrow key
KEY_SRSUME Shifted resume key
KEY_SSAVE Shifted save key
KEY_SSUSPEND Shifted suspend key
KEY_SUNDO Shifted undo key
Many keyboards feature a nine-key directional pad.
+------+------+-------+
| A1 | up | A3 |
+------+------+-------+
| left | B2 | right |
+------+------+-------+
| C1 | down | C3 |
+------+------+-------+
Two of the symbols in the list above do not correspond to a physical key.
o wgetch returns KEY_RESIZE, even if the window's keypad mode is
disabled, if ncurses has handled a SIGWINCH signal since wgetch was
called; see initscr(3X) and resizeterm(3X).
o wgetch returns KEY_MOUSE to indicate that a mouse event is pending
collection; see curs_mouse(3X). Receipt of this code requires a
window's keypad mode to be enabled, because to interpret mouse input
(as with xterm(1)'s mouse protocol), ncurses must read an escape
sequence, as with a function key.
Testing Key Codes
In ncurses, has_key returns a Boolean value indicating whether the
terminal type recognizes its parameter as a key code value. See also
define_key(3X) and key_defined(3X).
RETURN VALUE
wgetch returns a key code identifying the key event as described above,
which may include KEY_RESIZE or KEY_MOUSE indicating non-key events, or
ERR on failure. wgetch fails if its timeout expires without any data
arriving, which cannot happen if nodelay(3X) is in effect on the window.
In ncurses, wgetch also fails if
o the curses screen has not been initialized,
o (for functions taking a WINDOW pointer argument) win is a null
pointer, or
o execution was interrupted by a signal, in which case the library sets
errno to EINTR.
Functions prefixed with "mv" first perform cursor movement and fail if
the position (y, x) is outside the window boundaries.
ungetch returns OK on success and ERR on failure. In ncurses, ungetch
fails if
o the curses screen has not been initialized, or
o there is no more room in the input queue.
has_key returns TRUE or FALSE.
NOTES
getch, mvgetch, and mvwgetch may be implemented as macros.
curses discourages assignment of the ESC key to a discrete function by
the programmer because the library requires a delay while it awaits the
potential remainder of a terminal escape sequence.
Some key strokes are indistinguishable from control characters; for
example, KEY_ENTER may be the same as ^M, and KEY_BACKSPACE may be the
same as ^H or ^?. Consult the terminfo entry for the terminal type to
determine whether this is the case; see infocmp(1). Some curses
implementations, including ncurses, honor the terminfo key definitions;
others treat such control characters specially.
curses distinguishes the Enter keys in the alphabetic and numeric keypad
sections of a keyboard because (most) terminals do. KEY_ENTER refers to
the key on the numeric keypad and, like other function keys, is reliably
recognized only if the window's keypad mode is enabled.
o The terminfo key_enter (kent) capability describes the character
(sequence) sent by the Enter key of a terminal's numeric (or similar)
keypad.
o "Enter or send" is X/Open Curses's description of this key.
curses treats the Enter or Return key in the alphabetic section of the
keyboard differently.
o It usually produces a control code for carriage return (^M) or line
feed (^J).
o Depending on the terminal mode (raw, cbreak, or canonical), and
whether nl(3X) or nonl(3X) has been called, wgetch may return either
a carriage return or line feed upon an Enter or Return key stroke.
Use of wgetch with echo(3X) and neither cbreak(3X) nor raw(3X) is not
well-defined.
Historically, the list of key code macros above was influenced by the
keyboard of the AT&T 7300 (also known variously as the "3B1", "Safari 4",
and "UNIX PC"), a 1985 machine rich in function keys. Today's computer
keyboards are based on that of the IBM PC/AT and tend to have fewer. A
curses application can expect such a keyboard to transmit key codes
KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT, KEY_HOME, KEY_END, KEY_PPAGE (Page
Up), KEY_NPAGE (Page Down), KEY_IC (Insert), KEY_DC (Delete), KEY_A1,
KEY_A3, KEY_B2, KEY_C1, KEY_C3, and KEY_F(n) for 1 <= n <= 12.
EXTENSIONS
In ncurses, when a window's "no time-out" mode is not set, the ESCDELAY
variable configures the duration of the timer used to disambiguate a
function key character sequence from a series of key strokes beginning
with ESC typed by the user; see curs_variables(3X).
has_key is an ncurses extension, and is not found in SVr4 curses, 4.4BSD
curses, or any other previous curses implementation.
PORTABILITY
Applications employing ncurses extensions should condition their use on
the visibility of the NCURSES_VERSION preprocessor macro.
Except as noted in section "EXTENSIONS" above, X/Open Curses Issue 4
describes these functions. It specifies no error conditions for them.
SVr4 describes a successful return value only as "an integer value other
than ERR".
wgetch reads only single-byte characters.
The echo behavior of these functions on input of KEY_ or backspace
characters is not documented in SVr4 curses.
The behavior of wgetch in the presence of signal handlers is not
documented in SVr4 curses and is unspecified by X/Open Curses. In
historical curses implementations, it varied depending on whether the
operating system's dispatch of a signal to a handler interrupted a
read(2) call in progress, and also (in some implementations) whether an
input timeout or non-blocking mode had been set. A portable curses
application prepares for two cases: (a) signal receipt does not interrupt
wgetch; and (b) signal receipt interrupts wgetch and causes it to return
ERR with errno set to EINTR.
KEY_MOUSE is mentioned in X/Open Curses, along with a few related
terminfo capabilities, but no higher-level functions use the feature.
The implementation in ncurses is an extension.
KEY_RESIZE and has_key are extensions first implemented for ncurses. By
2022, PDCurses and NetBSD curses had added them along with KEY_MOUSE.
HISTORY
4BSD (1980) introduced wgetch and its variants.
SVr3 (1987) added ungetch.
ncurses 1.9.9g (1996) furnished the has_key extension.
SEE ALSO
ECMA-6 "7-bit coded Character Set" <https://ecma-international.org/
publications-and-standards/standards/ecma-6/>
ECMA-48 "Control Functions for Coded Character Sets" <https://
ecma-international.org/publications-and-standards/standards/ecma-48/>
curs_get_wch(3X) describes comparable functions of the ncurses library in
its wide-character configuration (ncursesw).
curses(3X), curs_addch(3X), curs_inopts(3X), curs_mouse(3X),
curs_move(3X), curs_outopts(3X), curs_refresh(3X), curs_variables(3X),
resizeterm(3X), ascii(7)
ncurses 6.6 2025-11-11 curs_getch(3X)