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

  Reading characters
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.

If echo is enabled, and the window is not a pad, 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. 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. 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 presses the escape key and the escape is returned to the program.

  Ungetting characters

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.

  Predefined key-codes
The following special keys, defined in <curses.h>, may be returned by getch if keypad has been enabled. Not all of these are necessarily supported on any particular terminal.

For 0 ≤ n ≤ 63
.nr 3crow 0
NameKey name
.nr 3brule 1
]
.nr 3brule 0
.nr 3crow 1
KEY_BREAKBreak key
.nr 3brule 1
.nr 3crow 2
KEY_DOWNThe four arrow keys ...
.nr 3brule 1
.nr 3crow 3
KEY_UP
.nr 3brule 1
.nr 3crow 4
KEY_LEFT
.nr 3brule 1
.nr 3crow 5
KEY_RIGHT
.nr 3brule 1
.nr 3crow 6
KEY_HOMEHome key (upward+left arrow)
.nr 3brule 1
.nr 3crow 7
KEY_BACKSPACEBackspace
.nr 3brule 1
.nr 3crow 8
KEY_F0
.nr 3brule 1
.nr 3crow 9
KEY_F(n)
.nr 3brule 1
.nr 3crow 10
KEY_DLDelete line
.nr 3brule 1
.nr 3crow 11
KEY_ILInsert line
.nr 3brule 1
.nr 3crow 12
KEY_DCDelete character
.nr 3brule 1
.nr 3crow 13
KEY_ICInsert char or enter insert mode
.nr 3brule 1
.nr 3crow 14
KEY_EICExit insert char mode
.nr 3brule 1
.nr 3crow 15
KEY_CLEARClear screen
.nr 3brule 1
.nr 3crow 16
KEY_EOSClear to end of screen
.nr 3brule 1
.nr 3crow 17
KEY_EOLClear to end of line
.nr 3brule 1
.nr 3crow 18
KEY_SFScroll 1 line forward
.nr 3brule 1
.nr 3crow 19
KEY_SRScroll 1 line backward (reverse)
.nr 3brule 1
.nr 3crow 20
KEY_NPAGENext page
.nr 3brule 1
.nr 3crow 21
KEY_PPAGEPrevious page
.nr 3brule 1
.nr 3crow 22
KEY_STABSet tab
.nr 3brule 1
.nr 3crow 23
KEY_CTABClear tab
.nr 3brule 1
.nr 3crow 24
KEY_CATABClear all tabs
.nr 3brule 1
.nr 3crow 25
KEY_ENTEREnter or send
.nr 3brule 1
.nr 3crow 26
KEY_SRESETSoft (partial) reset
.nr 3brule 1
.nr 3crow 27
KEY_RESETReset or hard reset
.nr 3brule 1
.nr 3crow 28
KEY_PRINTPrint or copy
.nr 3brule 1
.nr 3crow 29
KEY_LLHome down or bottom (lower left)
.nr 3brule 1
.nr 3crow 30
KEY_A1Upper left of keypad
.nr 3brule 1
.nr 3crow 31
KEY_A3Upper right of keypad
.nr 3brule 1
.nr 3crow 32
KEY_B2Center of keypad
.nr 3brule 1
.nr 3crow 33
KEY_C1Lower left of keypad
.nr 3brule 1
.nr 3crow 34
KEY_C3Lower right of keypad
.nr 3brule 1
.nr 3crow 35
KEY_BTABBack tab key
.nr 3brule 1
.nr 3crow 36
KEY_BEGBeg(inning) key
.nr 3brule 1
.nr 3crow 37
KEY_CANCELCancel key
.nr 3brule 1
.nr 3crow 38
KEY_CLOSEClose key
.nr 3brule 1
.nr 3crow 39
KEY_COMMANDCmd (command) key
.nr 3brule 1
.nr 3crow 40
KEY_COPYCopy key
.nr 3brule 1
.nr 3crow 41
KEY_CREATECreate key
.nr 3brule 1
.nr 3crow 42
KEY_ENDEnd key
.nr 3brule 1
.nr 3crow 43
KEY_EXITExit key
.nr 3brule 1
.nr 3crow 44
KEY_FINDFind key
.nr 3brule 1
.nr 3crow 45
KEY_HELPHelp key
.nr 3brule 1
.nr 3crow 46
KEY_MARKMark key
.nr 3brule 1
.nr 3crow 47
KEY_MESSAGEMessage key
.nr 3brule 1
.nr 3crow 48
KEY_MOUSEMouse event read
.nr 3brule 1
.nr 3crow 49
KEY_MOVEMove key
.nr 3brule 1
.nr 3crow 50
KEY_NEXTNext object key
.nr 3brule 1
.nr 3crow 51
KEY_OPENOpen key
.nr 3brule 1
.nr 3crow 52
KEY_OPTIONSOptions key
.nr 3brule 1
.nr 3crow 53
KEY_PREVIOUSPrevious object key
.nr 3brule 1
.nr 3crow 54
KEY_REDORedo key
.nr 3brule 1
.nr 3crow 55
KEY_REFERENCERef(erence) key
.nr 3brule 1
.nr 3crow 56
KEY_REFRESHRefresh key
.nr 3brule 1
.nr 3crow 57
KEY_REPLACEReplace key
.nr 3brule 1
.nr 3crow 58
KEY_RESIZEScreen resized
.nr 3brule 1
.nr 3crow 59
KEY_RESTARTRestart key
.nr 3brule 1
.nr 3crow 60
KEY_RESUMEResume key
.nr 3brule 1
.nr 3crow 61
KEY_SAVESave key
.nr 3brule 1
.nr 3crow 62
KEY_SBEGShifted beginning key
.nr 3brule 1
.nr 3crow 63
KEY_SCANCELShifted cancel key
.nr 3brule 1
.nr 3crow 64
KEY_SCOMMANDShifted command key
.nr 3brule 1
.nr 3crow 65
KEY_SCOPYShifted copy key
.nr 3brule 1
.nr 3crow 66
KEY_SCREATEShifted create key
.nr 3brule 1
.nr 3crow 67
KEY_SDCShifted delete char key
.nr 3brule 1
.nr 3crow 68
KEY_SDLShifted delete line key
.nr 3brule 1
.nr 3crow 69
KEY_SELECTSelect key
.nr 3brule 1
.nr 3crow 70
KEY_SENDShifted end key
.nr 3brule 1
.nr 3crow 71
KEY_SEOLShifted clear line key
.nr 3brule 1
.nr 3crow 72
KEY_SEXITShifted exit key
.nr 3brule 1
.nr 3crow 73
KEY_SFINDShifted find key
.nr 3brule 1
.nr 3crow 74
KEY_SHELPShifted help key
.nr 3brule 1
.nr 3crow 75
KEY_SHOMEShifted home key
.nr 3brule 1
.nr 3crow 76
KEY_SICShifted input key
.nr 3brule 1
.nr 3crow 77
KEY_SLEFTShifted left arrow key
.nr 3brule 1
.nr 3crow 78
KEY_SMESSAGEShifted message key
.nr 3brule 1
.nr 3crow 79
KEY_SMOVEShifted move key
.nr 3brule 1
.nr 3crow 80
KEY_SNEXTShifted next key
.nr 3brule 1
.nr 3crow 81
KEY_SOPTIONSShifted options key
.nr 3brule 1
.nr 3crow 82
KEY_SPREVIOUSShifted prev key
.nr 3brule 1
.nr 3crow 83
KEY_SPRINTShifted print key
.nr 3brule 1
.nr 3crow 84
KEY_SREDOShifted redo key
.nr 3brule 1
.nr 3crow 85
KEY_SREPLACEShifted replace key
.nr 3brule 1
.nr 3crow 86
KEY_SRIGHTShifted right arrow
.nr 3brule 1
.nr 3crow 87
KEY_SRSUMEShifted resume key
.nr 3brule 1
.nr 3crow 88
KEY_SSAVEShifted save key
.nr 3brule 1
.nr 3crow 89
KEY_SSUSPENDShifted suspend key
.nr 3brule 1
.nr 3crow 90
KEY_SUNDOShifted undo key
.nr 3brule 1
.nr 3crow 91
KEY_SUSPENDSuspend key
.nr 3brule 1
.nr 3crow 92
KEY_UNDOUndo key
.nr 3brule 1

Keypad is arranged like this:

A few of these predefined values do not correspond to a real key: KEY_RESIZE is returned when the SIGWINCH signal has been detected (see initscr(3X) and resizeterm(3X)). KEY_MOUSE is returned for mouse-events (see curs_mouse(3X)).

  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 terminal type recognizes a key with that value.

The library also supports these extensions:

    define_key
        defines a key-code for a given string (see define_key(3X)).

    key_defined
        checks if there is a key-code defined for a given string (see key_defined(3X)).

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.

    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.

Functions with a "mv" prefix first perform a cursor movement using wmove, and return an error if the position is outside the window, or if the window pointer is null.

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.

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.

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 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 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 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 EINTR. 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.

SEE ALSO
curses(3X), curs_inopts(3X), curs_outopts(3X), curs_mouse(3X), curs_move(3X), curs_refresh(3X), resizeterm(3X).

Comparable functions in the wide-character (ncursesw) library are described in curs_get_wch(3X).