1curs_getch(3X)                                                  curs_getch(3X)
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3
4

NAME

6       getch, wgetch, mvgetch, mvwgetch, ungetch, has_key - get (or push back)
7       characters from curses terminal keyboard
8

SYNOPSIS

10       #include <curses.h>
11
12       int getch(void);
13       int wgetch(WINDOW *win);
14       int mvgetch(int y, int x);
15       int mvwgetch(WINDOW *win, int y, int x);
16       int ungetch(int ch);
17       int has_key(int ch);
18

DESCRIPTION

20   Reading characters
21       The getch, wgetch, mvgetch and mvwgetch, routines read a character from
22       the window.  In no-delay mode, if no input is waiting, the value ERR is
23       returned.  In delay mode, the program waits  until  the  system  passes
24       text  through to the program.  Depending on the setting of cbreak, this
25       is after one character  (cbreak  mode),  or  after  the  first  newline
26       (nocbreak mode).  In half-delay mode, the program waits until a charac‐
27       ter is typed or the specified timeout has been reached.
28
29       If echo is enabled, and the window is not a  pad,  then  the  character
30       will also be echoed into the designated window according to the follow‐
31       ing rules:
32
33       ·   If the character is the current erase  character,  left  arrow,  or
34           backspace,  the  cursor  is  moved  one  space to the left and that
35           screen position is erased as if delch had been called.
36
37       ·   If the character value is any other KEY_ define, the user is alert‐
38           ed with a beep call.
39
40       ·   If  the character is a carriage-return, and if nl is enabled, it is
41           translated to a line-feed after echoing.
42
43       ·   Otherwise the character is simply output to the screen.
44
45       If the window is not a pad, and it has been moved or modified since the
46       last call to wrefresh, wrefresh will be called before another character
47       is read.
48
49   Keypad mode
50       If keypad is TRUE, and a function key is pressed, the  token  for  that
51       function key is returned instead of the raw characters:
52
53       ·   The  predefined  function  keys  are listed in <curses.h> as macros
54           with values outside the range of 8-bit characters.  Their names be‐
55           gin with KEY_.
56
57       ·   Other  (user-defined)  function keys which may be defined using de‐
58           fine_key(3X) have no names, but also are expected  to  have  values
59           outside the range of 8-bit characters.
60
61       Thus,  a  variable  intended to hold the return value of a function key
62       must be of short size or larger.
63
64       When a character that could be the beginning of a function key  is  re‐
65       ceived  (which, on modern terminals, means an escape character), curses
66       sets a timer.  If the remainder of the sequence does not come in within
67       the  designated  time,  the character is passed through; otherwise, the
68       function key value is returned.  For this reason, many terminals  expe‐
69       rience  a  delay between the time a user presses the escape key and the
70       escape is returned to the program.
71
72       In ncurses, the timer normally expires after the value in ESCDELAY (see
73       curs_variables(3X)).   If notimeout is TRUE, the timer does not expire;
74       it is an infinite (or very large) value.  Because function keys usually
75       begin  with an escape character, the terminal may appear to hang in no‐
76       timeout mode after  pressing  the  escape  key  until  another  key  is
77       pressed.
78
79   Ungetting characters
80       The  ungetch routine places ch back onto the input queue to be returned
81       by the next call to wgetch.  There is just one input queue for all win‐
82       dows.
83
84   Predefined key-codes
85       The following special keys are defined in <curses.h>.
86
87       ·   Except  for  the special case KEY_RESIZE, it is necessary to enable
88           keypad for getch to return these codes.
89
90       ·   Not all of these are necessarily supported on any particular termi‐
91           nal.
92
93       ·   The  naming  convention  may  seem obscure, with some apparent mis‐
94           spellings (such as "RSUME" for "resume").  The names correspond  to
95           the  long  terminfo capability names for the keys, and were defined
96           long ago, in the 1980s.
97
98                  Name            Key name
99                  ─────────────────────────────────────────────────
100                  KEY_BREAK       Break key
101                  KEY_DOWN        The four arrow keys ...
102                  KEY_UP
103                  KEY_LEFT
104                  KEY_RIGHT
105                  KEY_HOME        Home key (upward+left arrow)
106                  KEY_BACKSPACE   Backspace
107                  KEY_F0          Function keys; space for 64 keys
108                                  is reserved.
109                  KEY_F(n)        For 0 ≤ n ≤ 63
110                  KEY_DL          Delete line
111                  KEY_IL          Insert line
112                  KEY_DC          Delete character
113                  KEY_IC          Insert char or enter insert mode
114                  KEY_EIC         Exit insert char mode
115                  KEY_CLEAR       Clear screen
116                  KEY_EOS         Clear to end of screen
117                  KEY_EOL         Clear to end of line
118                  KEY_SF          Scroll 1 line forward
119                  KEY_SR          Scroll 1 line backward (reverse)
120                  KEY_NPAGE       Next page
121                  KEY_PPAGE       Previous page
122                  KEY_STAB        Set tab
123                  KEY_CTAB        Clear tab
124                  KEY_CATAB       Clear all tabs
125                  KEY_ENTER       Enter or send
126                  KEY_SRESET      Soft (partial) reset
127                  KEY_RESET       Reset or hard reset
128                  KEY_PRINT       Print or copy
129                  KEY_LL          Home down or bottom (lower left)
130                  KEY_A1          Upper left of keypad
131                  KEY_A3          Upper right of keypad
132
133                  KEY_B2          Center of keypad
134                  KEY_C1          Lower left of keypad
135                  KEY_C3          Lower right of keypad
136                  KEY_BTAB        Back tab key
137                  KEY_BEG         Beg(inning) key
138                  KEY_CANCEL      Cancel key
139                  KEY_CLOSE       Close key
140                  KEY_COMMAND     Cmd (command) key
141                  KEY_COPY        Copy key
142                  KEY_CREATE      Create key
143                  KEY_END         End key
144                  KEY_EXIT        Exit key
145                  KEY_FIND        Find key
146                  KEY_HELP        Help key
147                  KEY_MARK        Mark key
148                  KEY_MESSAGE     Message key
149                  KEY_MOUSE       Mouse event read
150                  KEY_MOVE        Move key
151                  KEY_NEXT        Next object key
152                  KEY_OPEN        Open key
153                  KEY_OPTIONS     Options key
154                  KEY_PREVIOUS    Previous object key
155                  KEY_REDO        Redo key
156                  KEY_REFERENCE   Ref(erence) key
157                  KEY_REFRESH     Refresh key
158                  KEY_REPLACE     Replace key
159                  KEY_RESIZE      Screen resized
160                  KEY_RESTART     Restart key
161                  KEY_RESUME      Resume key
162                  KEY_SAVE        Save key
163                  KEY_SBEG        Shifted beginning key
164                  KEY_SCANCEL     Shifted cancel key
165                  KEY_SCOMMAND    Shifted command key
166                  KEY_SCOPY       Shifted copy key
167                  KEY_SCREATE     Shifted create key
168                  KEY_SDC         Shifted delete char key
169                  KEY_SDL         Shifted delete line key
170                  KEY_SELECT      Select key
171                  KEY_SEND        Shifted end key
172                  KEY_SEOL        Shifted clear line key
173                  KEY_SEXIT       Shifted exit key
174                  KEY_SFIND       Shifted find key
175                  KEY_SHELP       Shifted help key
176                  KEY_SHOME       Shifted home key
177                  KEY_SIC         Shifted input key
178                  KEY_SLEFT       Shifted left arrow key
179                  KEY_SMESSAGE    Shifted message key
180                  KEY_SMOVE       Shifted move key
181                  KEY_SNEXT       Shifted next key
182                  KEY_SOPTIONS    Shifted options key
183                  KEY_SPREVIOUS   Shifted prev key
184                  KEY_SPRINT      Shifted print key
185                  KEY_SREDO       Shifted redo key
186                  KEY_SREPLACE    Shifted replace key
187                  KEY_SRIGHT      Shifted right arrow
188                  KEY_SRSUME      Shifted resume key
189                  KEY_SSAVE       Shifted save key
190                  KEY_SSUSPEND    Shifted suspend key
191                  KEY_SUNDO       Shifted undo key
192                  KEY_SUSPEND     Suspend key
193                  KEY_UNDO        Undo key
194
195       Keypad is arranged like this:
196
197                                ┌─────┬──────┬───────┐
198A1  up  A3   
199                                ├─────┼──────┼───────┤
200left B2  right 
201                                ├─────┼──────┼───────┤
202C1  down C3   
203                                └─────┴──────┴───────┘
204       A few of these predefined values do not correspond to a real key:
205
206       ·   KEY_RESIZE  is  returned when the SIGWINCH signal has been detected
207           (see  initscr(3X)  and  resizeterm(3X)).   This  code  is  returned
208           whether or not keypad has been enabled.
209
210       ·   KEY_MOUSE  is returned for mouse-events (see curs_mouse(3X)).  This
211           code relies upon whether or not keypad(3X) has  been  enabled,  be‐
212           cause  (e.g., with xterm mouse prototocol) ncurses must read escape
213           sequences, just like a function key.
214
215   Testing key-codes
216       The has_key routine takes a key-code value from the above list, and re‐
217       turns TRUE or FALSE according to whether the current terminal type rec‐
218       ognizes a key with that value.
219
220       The library also supports these extensions:
221
222          define_key
223               defines a key-code for a given string (see define_key(3X)).
224
225          key_defined
226               checks if there is a key-code defined for a given  string  (see
227               key_defined(3X)).
228

RETURN VALUE

230       All  routines  return the integer ERR upon failure and an integer value
231       other than ERR (OK in the case of ungetch) upon successful completion.
232
233          ungetch
234               returns ERR if there is no more room in the FIFO.
235
236          wgetch
237               returns ERR if the window pointer is null, or  if  its  timeout
238               expires without having any data, or if the execution was inter‐
239               rupted by a signal (errno will be set to EINTR).
240
241       Functions with a "mv" prefix first  perform  a  cursor  movement  using
242       wmove, and return an error if the position is outside the window, or if
243       the window pointer is null.
244

NOTES

246       Use of the escape key by a programmer for a single  character  function
247       is  discouraged, as it will cause a delay of up to one second while the
248       keypad code looks for a following function-key sequence.
249
250       Some keys may be the same as commonly used control keys, e.g.,  KEY_EN‐
251       TER  versus control/M, KEY_BACKSPACE versus control/H.  Some curses im‐
252       plementations may differ according to whether they treat these  control
253       keys  specially  (and ignore the terminfo), or use the terminfo defini‐
254       tions.  Ncurses uses the terminfo definition.  If it says that  KEY_EN‐
255       TER is control/M, getch will return KEY_ENTER when you press control/M.
256
257       Generally,  KEY_ENTER denotes the character(s) sent by the Enter key on
258       the numeric keypad:
259
260       ·   the terminal description lists the most useful keys,
261
262       ·   the Enter key on the regular keyboard is  already  handled  by  the
263           standard ASCII characters for carriage-return and line-feed,
264
265       ·   depending on whether nl or nonl was called, pressing "Enter" on the
266           regular keyboard may return either a carriage-return or  line-feed,
267           and finally
268
269       ·   "Enter or send" is the standard description for this key.
270
271       When   using   getch,  wgetch,  mvgetch,  or  mvwgetch,  nocbreak  mode
272       (nocbreak) and echo mode (echo) should not be used at  the  same  time.
273       Depending  on the state of the tty driver when each character is typed,
274       the program may produce undesirable results.
275
276       Note that getch, mvgetch, and mvwgetch may be macros.
277
278       Historically, the set of keypad macros was largely defined by  the  ex‐
279       tremely  function-key-rich  keyboard of the AT&T 7300, aka 3B1, aka Sa‐
280       fari 4.  Modern personal computers usually have only a small subset  of
281       these.   IBM  PC-style  consoles  typically  support  little  more than
282       KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT,  KEY_HOME,  KEY_END,  KEY_NPAGE,
283       KEY_PPAGE,  and  function  keys  1  through 12.  The Ins key is usually
284       mapped to KEY_IC.
285

PORTABILITY

287       The *get* functions are described in the XSI Curses standard, Issue  4.
288       They  read  single-byte  characters  only.  The standard specifies that
289       they return ERR on failure, but specifies no error conditions.
290
291       The echo behavior of these functions on  input  of  KEY_  or  backspace
292       characters  was not specified in the SVr4 documentation.  This descrip‐
293       tion is adopted from the XSI Curses standard.
294
295       The behavior of getch and friends in the presence of handled signals is
296       unspecified in the SVr4 and XSI Curses documentation.  Under historical
297       curses implementations, it varied depending on  whether  the  operating
298       system's  implementation of handled signal receipt interrupts a read(2)
299       call in progress or not, and also (in some  implementations)  depending
300       on whether an input timeout or non-blocking mode has been set.
301
302       KEY_MOUSE is mentioned in XSI Curses, along with a few related terminfo
303       capabilities, but no higher-level functions use the feature.   The  im‐
304       plementation in ncurses is an extension.
305
306       KEY_RESIZE is an extension first implemented for ncurses.  NetBSD curs‐
307       es later added this extension.
308
309       Programmers concerned about portability should be prepared  for  either
310       of  two  cases: (a) signal receipt does not interrupt getch; (b) signal
311       receipt interrupts getch and causes it to return ERR with errno set  to
312       EINTR.
313
314       The  has_key function is unique to ncurses.  We recommend that any code
315       using it be conditionalized on the NCURSES_VERSION feature macro.
316

SEE ALSO

318       curses(3X),    curs_inopts(3X),    curs_outopts(3X),    curs_mouse(3X),
319       curs_move(3X), curs_refresh(3X), curs_variables(3X), resizeterm(3X).
320
321       Comparable  functions  in the wide-character (ncursesw) library are de‐
322       scribed in curs_get_wch(3X).
323
324
325
326                                                                curs_getch(3X)
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