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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | COLOPHON |
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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);
/* extension */
int has_key(int ch);
Reading characters
The getch, wgetch, mvgetch and mvwgetch, routines read a charac‐
ter from the window. In no-delay mode, if no input is waiting,
the value ERR is returned. In delay mode, the program waits un‐
til 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 character is typed or the specified
timeout has been reached.
If echo is enabled, and the window is not a pad, then the charac‐
ter 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.
• If the character is a carriage-return, and if nl is enabled,
it is translated to a line-feed after echoing.
• 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.
Keypad mode
If keypad is TRUE, and a function key is pressed, the token for
that function key is returned instead of the raw characters:
• The predefined function keys are listed in <curses.h> as
macros with values outside the range of 8-bit characters.
Their names begin with KEY_.
• Other (user-defined) function keys which may be defined 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 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
presses the escape key and the escape is returned to the program.
In ncurses, the timer normally expires after the value in ESCDE‐
LAY (see curs_variables(3X)). If notimeout is TRUE, the timer
does not expire; it is an infinite (or very large) value. Be‐
cause function keys usually begin with an escape character, the
terminal may appear to hang in notimeout mode after pressing the
escape key until another key is pressed.
Ungetting characters
The ungetch routine places ch back onto the input queue to be re‐
turned by the next call to wgetch. There is just one input queue
for all windows.
Predefined key-codes
The following special keys are defined in <curses.h>.
• Except for the special case KEY_RESIZE, it is necessary to
enable keypad for getch to return these codes.
• Not all of these are necessarily supported on any particular
terminal.
• The naming convention may seem obscure, with some apparent
misspellings (such as “RSUME” for “resume”). The names cor‐
respond 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 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_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 insert 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
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:
• KEY_RESIZE is returned when the SIGWINCH signal has been de‐
tected (see initscr(3X) and resizeterm(3X)). This code is
returned whether or not keypad has been enabled.
• KEY_MOUSE is returned for mouse-events (see curs_mouse(3X)).
This code relies upon whether or not keypad(3X) has been en‐
abled, because (e.g., with xterm(1) mouse prototocol) ncurses
must read escape sequences, just like a function key.
Testing key-codes
The has_key routine takes a key-code value from the above list,
and returns TRUE or FALSE according to whether the current termi‐
nal 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, or if the execu‐
tion was interrupted by a signal (errno will be set to
EINTR).
Functions with a “mv” prefix first perform a cursor movement us‐
ing 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 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.
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_EN‐
TER when you press control/M.
Generally, KEY_ENTER denotes the character(s) sent by the Enter
key on the numeric keypad:
• the terminal description lists the most useful keys,
• the Enter key on the regular keyboard is already handled by
the standard ASCII characters for carriage-return and line-
feed,
• 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
• “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 charac‐
ter 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.
The *get* functions are described in the XSI Curses standard, Is‐
sue 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 back‐
space characters was not specified in the SVr4 documentation.
This description is adopted from the XSI Curses standard.
The behavior of getch and friends in the presence of handled sig‐
nals 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.
KEY_MOUSE is mentioned in XSI Curses, along with a few related
terminfo capabilities, but no higher-level functions use the fea‐
ture. The implementation in ncurses is an extension.
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 interrupt getch;
(b) signal receipt interrupts getch and causes it to return ERR
with errno set to EINTR.
The has_key function is unique to ncurses. We recommend that any
code using it be conditionalized on the NCURSES_VERSION feature
macro.
curses(3X), curs_inopts(3X), curs_mouse(3X), curs_move(3X),
curs_outopts(3X), curs_refresh(3X), curs_variables(3X), re‐
sizeterm(3X).
Comparable functions in the wide-character (ncursesw) library are
described in curs_get_wch(3X).
This page is part of the ncurses (new curses) project. Informa‐
tion about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
curs_getch(3X)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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