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
15       int mvgetch(int y, int x);
16       int mvwgetch(WINDOW *win, int y, int x);
17
18       int ungetch(int ch);
19
20       /* extension */
21       int has_key(int ch);
22

DESCRIPTION

24   Reading characters
25       The getch, wgetch, mvgetch and mvwgetch, routines read a character from
26       the window.  In no-delay mode, if no input is waiting, the value ERR is
27       returned.  In delay mode, the program waits  until  the  system  passes
28       text  through to the program.  Depending on the setting of cbreak, this
29       is after one character  (cbreak  mode),  or  after  the  first  newline
30       (nocbreak mode).  In half-delay mode, the program waits until a charac‐
31       ter is typed or the specified timeout has been reached.
32
33       If echo is enabled, and the window is not a  pad,  then  the  character
34       will also be echoed into the designated window according to the follow‐
35       ing rules:
36
37       •   If the character is the current erase  character,  left  arrow,  or
38           backspace,  the  cursor  is  moved  one  space to the left and that
39           screen position is erased as if delch had been called.
40
41       •   If the character value is any other KEY_ define, the user is alert‐
42           ed with a beep call.
43
44       •   If  the character is a carriage-return, and if nl is enabled, it is
45           translated to a line-feed after echoing.
46
47       •   Otherwise the character is simply output to the screen.
48
49       If the window is not a pad, and it has been moved or modified since the
50       last call to wrefresh, wrefresh will be called before another character
51       is read.
52
53   Keypad mode
54       If keypad is TRUE, and a function key is pressed, the  token  for  that
55       function key is returned instead of the raw characters:
56
57       •   The  predefined  function  keys  are listed in <curses.h> as macros
58           with values outside the range of 8-bit characters.  Their names be‐
59           gin with KEY_.
60
61       •   Other  (user-defined)  function keys which may be defined using de‐
62           fine_key(3X) have no names, but also are expected  to  have  values
63           outside the range of 8-bit characters.
64
65       Thus,  a  variable  intended to hold the return value of a function key
66       must be of short size or larger.
67
68       When a character that could be the beginning of a function key  is  re‐
69       ceived  (which, on modern terminals, means an escape character), curses
70       sets a timer.  If the remainder of the sequence does not come in within
71       the  designated  time,  the character is passed through; otherwise, the
72       function key value is returned.  For this reason, many terminals  expe‐
73       rience  a  delay between the time a user presses the escape key and the
74       escape is returned to the program.
75
76       In ncurses, the timer normally expires after the value in ESCDELAY (see
77       curs_variables(3X)).   If notimeout is TRUE, the timer does not expire;
78       it is an infinite (or very large) value.  Because function keys usually
79       begin  with an escape character, the terminal may appear to hang in no‐
80       timeout mode after  pressing  the  escape  key  until  another  key  is
81       pressed.
82
83   Ungetting characters
84       The  ungetch routine places ch back onto the input queue to be returned
85       by the next call to wgetch.  There is just one input queue for all win‐
86       dows.
87
88   Predefined key-codes
89       The following special keys are defined in <curses.h>.
90
91       •   Except  for  the special case KEY_RESIZE, it is necessary to enable
92           keypad for getch to return these codes.
93
94       •   Not all of these are necessarily supported on any particular termi‐
95           nal.
96
97       •   The  naming  convention  may  seem obscure, with some apparent mis‐
98           spellings (such as “RSUME” for “resume”).  The names correspond  to
99           the  long  terminfo capability names for the keys, and were defined
100           long ago, in the 1980s.
101
102                  Name            Key name
103                  ─────────────────────────────────────────────────
104                  KEY_BREAK       Break key
105                  KEY_DOWN        The four arrow keys ...
106                  KEY_UP
107                  KEY_LEFT
108                  KEY_RIGHT
109                  KEY_HOME        Home key (upward+left arrow)
110                  KEY_BACKSPACE   Backspace
111                  KEY_F0          Function keys; space for 64 keys
112                                  is reserved.
113                  KEY_F(n)        For 0 ≤ n ≤ 63
114                  KEY_DL          Delete line
115                  KEY_IL          Insert line
116                  KEY_DC          Delete character
117                  KEY_IC          Insert char or enter insert mode
118                  KEY_EIC         Exit insert char mode
119                  KEY_CLEAR       Clear screen
120                  KEY_EOS         Clear to end of screen
121                  KEY_EOL         Clear to end of line
122                  KEY_SF          Scroll 1 line forward
123                  KEY_SR          Scroll 1 line backward (reverse)
124                  KEY_NPAGE       Next page
125                  KEY_PPAGE       Previous page
126                  KEY_STAB        Set tab
127                  KEY_CTAB        Clear tab
128                  KEY_CATAB       Clear all tabs
129                  KEY_ENTER       Enter or send
130                  KEY_SRESET      Soft (partial) reset
131                  KEY_RESET       Reset or hard reset
132
133                  KEY_PRINT       Print or copy
134                  KEY_LL          Home down or bottom (lower left)
135                  KEY_A1          Upper left of keypad
136                  KEY_A3          Upper right of keypad
137                  KEY_B2          Center of keypad
138                  KEY_C1          Lower left of keypad
139                  KEY_C3          Lower right of keypad
140                  KEY_BTAB        Back tab key
141                  KEY_BEG         Beg(inning) key
142                  KEY_CANCEL      Cancel key
143                  KEY_CLOSE       Close key
144                  KEY_COMMAND     Cmd (command) key
145                  KEY_COPY        Copy key
146                  KEY_CREATE      Create key
147                  KEY_END         End key
148                  KEY_EXIT        Exit key
149                  KEY_FIND        Find key
150                  KEY_HELP        Help key
151                  KEY_MARK        Mark key
152                  KEY_MESSAGE     Message key
153                  KEY_MOUSE       Mouse event read
154                  KEY_MOVE        Move key
155                  KEY_NEXT        Next object key
156                  KEY_OPEN        Open key
157                  KEY_OPTIONS     Options key
158                  KEY_PREVIOUS    Previous object key
159                  KEY_REDO        Redo key
160                  KEY_REFERENCE   Ref(erence) key
161                  KEY_REFRESH     Refresh key
162                  KEY_REPLACE     Replace key
163                  KEY_RESIZE      Screen resized
164                  KEY_RESTART     Restart key
165                  KEY_RESUME      Resume key
166                  KEY_SAVE        Save key
167                  KEY_SBEG        Shifted beginning key
168                  KEY_SCANCEL     Shifted cancel key
169                  KEY_SCOMMAND    Shifted command key
170                  KEY_SCOPY       Shifted copy key
171                  KEY_SCREATE     Shifted create key
172                  KEY_SDC         Shifted delete char key
173                  KEY_SDL         Shifted delete line key
174                  KEY_SELECT      Select key
175                  KEY_SEND        Shifted end key
176                  KEY_SEOL        Shifted clear line key
177                  KEY_SEXIT       Shifted exit key
178                  KEY_SFIND       Shifted find key
179                  KEY_SHELP       Shifted help key
180                  KEY_SHOME       Shifted home key
181                  KEY_SIC         Shifted input key
182                  KEY_SLEFT       Shifted left arrow key
183                  KEY_SMESSAGE    Shifted message key
184                  KEY_SMOVE       Shifted move key
185                  KEY_SNEXT       Shifted next key
186                  KEY_SOPTIONS    Shifted options key
187                  KEY_SPREVIOUS   Shifted prev key
188                  KEY_SPRINT      Shifted print key
189                  KEY_SREDO       Shifted redo key
190                  KEY_SREPLACE    Shifted replace key
191                  KEY_SRIGHT      Shifted right arrow
192                  KEY_SRSUME      Shifted resume key
193                  KEY_SSAVE       Shifted save key
194                  KEY_SSUSPEND    Shifted suspend key
195                  KEY_SUNDO       Shifted undo key
196                  KEY_SUSPEND     Suspend key
197                  KEY_UNDO        Undo key
198
199       Keypad is arranged like this:
200
201                                ┌─────┬──────┬───────┐
202A1  up  A3   
203                                ├─────┼──────┼───────┤
204left B2  right 
205                                ├─────┼──────┼───────┤
206C1  down C3   
207                                └─────┴──────┴───────┘
208       A few of these predefined values do not correspond to a real key:
209
210KEY_RESIZE  is  returned when the SIGWINCH signal has been detected
211           (see  initscr(3X)  and  resizeterm(3X)).   This  code  is  returned
212           whether or not keypad has been enabled.
213
214KEY_MOUSE  is returned for mouse-events (see curs_mouse(3X)).  This
215           code relies upon whether or not keypad(3X) has  been  enabled,  be‐
216           cause  (e.g., with xterm mouse prototocol) ncurses must read escape
217           sequences, just like a function key.
218
219   Testing key-codes
220       The has_key routine takes a key-code value from the above list, and re‐
221       turns TRUE or FALSE according to whether the current terminal type rec‐
222       ognizes a key with that value.
223
224       The library also supports these extensions:
225
226          define_key
227               defines a key-code for a given string (see define_key(3X)).
228
229          key_defined
230               checks if there is a key-code defined for a given  string  (see
231               key_defined(3X)).
232

RETURN VALUE

234       All  routines  return the integer ERR upon failure and an integer value
235       other than ERR (OK in the case of ungetch) upon successful completion.
236
237          ungetch
238               returns ERR if there is no more room in the FIFO.
239
240          wgetch
241               returns ERR if the window pointer is null, or  if  its  timeout
242               expires without having any data, or if the execution was inter‐
243               rupted by a signal (errno will be set to EINTR).
244
245       Functions with a “mv” prefix first  perform  a  cursor  movement  using
246       wmove, and return an error if the position is outside the window, or if
247       the window pointer is null.
248

NOTES

250       Use of the escape key by a programmer for a single  character  function
251       is  discouraged, as it will cause a delay of up to one second while the
252       keypad code looks for a following function-key sequence.
253
254       Some keys may be the same as commonly used control keys, e.g.,  KEY_EN‐
255       TER  versus control/M, KEY_BACKSPACE versus control/H.  Some curses im‐
256       plementations may differ according to whether they treat these  control
257       keys  specially  (and ignore the terminfo), or use the terminfo defini‐
258       tions.  Ncurses uses the terminfo definition.  If it says that  KEY_EN‐
259       TER is control/M, getch will return KEY_ENTER when you press control/M.
260
261       Generally,  KEY_ENTER denotes the character(s) sent by the Enter key on
262       the numeric keypad:
263
264       •   the terminal description lists the most useful keys,
265
266       •   the Enter key on the regular keyboard is  already  handled  by  the
267           standard ASCII characters for carriage-return and line-feed,
268
269       •   depending on whether nl or nonl was called, pressing “Enter” on the
270           regular keyboard may return either a carriage-return or  line-feed,
271           and finally
272
273       •   “Enter or send” is the standard description for this key.
274
275       When   using   getch,  wgetch,  mvgetch,  or  mvwgetch,  nocbreak  mode
276       (nocbreak) and echo mode (echo) should not be used at  the  same  time.
277       Depending  on the state of the tty driver when each character is typed,
278       the program may produce undesirable results.
279
280       Note that getch, mvgetch, and mvwgetch may be macros.
281
282       Historically, the set of keypad macros was largely defined by  the  ex‐
283       tremely  function-key-rich  keyboard of the AT&T 7300, aka 3B1, aka Sa‐
284       fari 4.  Modern personal computers usually have only a small subset  of
285       these.   IBM  PC-style  consoles  typically  support  little  more than
286       KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT,  KEY_HOME,  KEY_END,  KEY_NPAGE,
287       KEY_PPAGE,  and  function  keys  1  through 12.  The Ins key is usually
288       mapped to KEY_IC.
289

PORTABILITY

291       The *get* functions are described in the XSI Curses standard, Issue  4.
292       They  read  single-byte  characters  only.  The standard specifies that
293       they return ERR on failure, but specifies no error conditions.
294
295       The echo behavior of these functions on  input  of  KEY_  or  backspace
296       characters  was not specified in the SVr4 documentation.  This descrip‐
297       tion is adopted from the XSI Curses standard.
298
299       The behavior of getch and friends in the presence of handled signals is
300       unspecified in the SVr4 and XSI Curses documentation.  Under historical
301       curses implementations, it varied depending on  whether  the  operating
302       system's  implementation of handled signal receipt interrupts a read(2)
303       call in progress or not, and also (in some  implementations)  depending
304       on whether an input timeout or non-blocking mode has been set.
305
306       KEY_MOUSE is mentioned in XSI Curses, along with a few related terminfo
307       capabilities, but no higher-level functions use the feature.   The  im‐
308       plementation in ncurses is an extension.
309
310       KEY_RESIZE is an extension first implemented for ncurses.  NetBSD curs‐
311       es later added this extension.
312
313       Programmers concerned about portability should be prepared  for  either
314       of  two  cases: (a) signal receipt does not interrupt getch; (b) signal
315       receipt interrupts getch and causes it to return ERR with errno set  to
316       EINTR.
317
318       The  has_key function is unique to ncurses.  We recommend that any code
319       using it be conditionalized on the NCURSES_VERSION feature macro.
320

SEE ALSO

322       curses(3X), curs_inopts(3X), curs_mouse(3X),  curs_move(3X),  curs_out‐
323       opts(3X), curs_refresh(3X), curs_variables(3X), resizeterm(3X).
324
325       Comparable  functions  in the wide-character (ncursesw) library are de‐
326       scribed in curs_get_wch(3X).
327
328
329
330                                                                curs_getch(3X)
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