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Section: Miscellaneous Library Functions (3X)
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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 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.

Unless noecho has been set,
then the character 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.
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 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

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.

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.


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.

NameKey name
KEY_BREAKBreak key
KEY_DOWNThe four arrow keys …
KEY_HOMEHome key (upward+left arrow)
Function keys; space for 64 keys is reserved.

For 0 ≤ n ≤ 63

KEY_DLDelete line
KEY_ILInsert line
KEY_DCDelete character
KEY_ICInsert char or enter insert mode
KEY_EICExit insert char mode
KEY_CLEARClear screen
KEY_EOSClear to end of screen
KEY_EOLClear to end of line
KEY_SFScroll 1 line forward
KEY_SRScroll 1 line backward (reverse)
KEY_NPAGENext page
KEY_PPAGEPrevious page
KEY_CTABClear tab
KEY_CATABClear all tabs
KEY_ENTEREnter or send
KEY_SRESETSoft (partial) reset
KEY_RESETReset or hard reset
KEY_PRINTPrint or copy
KEY_LLHome down or bottom (lower left)
KEY_A1Upper left of keypad
KEY_A3Upper right of keypad
KEY_B2Center of keypad
KEY_C1Lower left of keypad
KEY_C3Lower right of keypad
KEY_BTABBack tab key
KEY_BEGBeg(inning) key
KEY_CANCELCancel key
KEY_CLOSEClose key
KEY_COMMANDCmd (command) key
KEY_COPYCopy key
KEY_CREATECreate key
KEY_ENDEnd key
KEY_EXITExit key
KEY_FINDFind key
KEY_HELPHelp key
KEY_MARKMark key
KEY_MESSAGEMessage key
KEY_MOUSEMouse event read
KEY_MOVEMove key
KEY_NEXTNext object key
KEY_OPENOpen key
KEY_OPTIONSOptions key
KEY_PREVIOUSPrevious object key
KEY_REDORedo key
KEY_REFERENCERef(erence) key
KEY_REFRESHRefresh key
KEY_REPLACEReplace key
KEY_RESIZEScreen resized
KEY_RESTARTRestart key
KEY_RESUMEResume key
KEY_SAVESave key
KEY_SBEGShifted beginning key
KEY_SCANCELShifted cancel key
KEY_SCOMMANDShifted command key
KEY_SCOPYShifted copy key
KEY_SCREATEShifted create key
KEY_SDCShifted delete char key
KEY_SDLShifted delete line key
KEY_SELECTSelect key
KEY_SENDShifted end key
KEY_SEOLShifted clear line key
KEY_SEXITShifted exit key
KEY_SFINDShifted find key
KEY_SHELPShifted help key
KEY_SHOMEShifted home key
KEY_SICShifted input key
KEY_SLEFTShifted left arrow key
KEY_SMESSAGEShifted message key
KEY_SMOVEShifted move key
KEY_SNEXTShifted next key
KEY_SOPTIONSShifted options key
KEY_SPREVIOUSShifted prev key
KEY_SPRINTShifted print key
KEY_SREDOShifted redo key
KEY_SREPLACEShifted replace key
KEY_SRIGHTShifted right arrow
KEY_SRSUMEShifted resume key
KEY_SSAVEShifted save key
KEY_SSUSPENDShifted suspend key
KEY_SUNDOShifted undo key
KEY_SUSPENDSuspend key
KEY_UNDOUndo key

Keypad is arranged like this:


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,
See resizeterm(3X) for more details about KEY_RESIZE, and
curs_mouse(3X) for a discussion of KEY_MOUSE.



All routines return the integer ERR upon failure and an integer value
other than ERR (OK in the case of ungetch()) upon successful


returns an error
if there is no more room in the FIFO.

returns an error
if the window pointer is null, or
if its timeout expires without having any data.



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 control/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 extremely
function-key-rich keyboard of the AT&T 7300, aka 3B1, aka Safari 4.
personal computers usually have only a small subset of these.
IBM PC-style
consoles typically support little more than KEY_UP, KEY_DOWN,
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, Issue 4.
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 description 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
Under the ncurses implementation, handled signals never
interrupt getch.

The has_key function is unique to ncurses.
We recommend that
any code using it be conditionalized on the NCURSES_VERSION feature macro.



Comparable functions in the wide-character (ncursesw) library are
described in






Function Keys





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