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30 .\" $Id: curs_getch.3x,v 1.49 2016/10/15 16:44:01 tom Exp $
31 .TH curs_getch 3X ""
32 .na
33 .hy 0
34 .de bP
35 .IP \(bu 4
36 ..
37 .SH NAME
38 \fBgetch\fR,
39 \fBwgetch\fR,
40 \fBmvgetch\fR,
41 \fBmvwgetch\fR,
42 \fBungetch\fR,
43 \fBhas_key\fR \- get (or push back) characters from \fBcurses\fR terminal keyboard
44 .ad
45 .hy
46 .SH SYNOPSIS
47 \fB#include <curses.h>\fR
48 .PP
49 \fBint getch(void);\fR
50 .br
51 \fBint wgetch(WINDOW *\fP\fIwin);\fR
52 .br
53 \fBint mvgetch(int \fP\fIy\fP\fB, int \fP\fIx\fP\fB);\fR
54 .br
55 \fBint mvwgetch(WINDOW *\fP\fIwin\fP\fB, int \fP\fIy\fP\fB, int \fP\fIx\fP\fB);\fR
56 .br
57 \fBint ungetch(int \fP\fIch\fP\fB);\fR
58 .br
59 \fBint has_key(int \fP\fIch\fP\fB);\fR
60 .br
61 .SH DESCRIPTION
62 .SS Reading characters
63 The \fBgetch\fR, \fBwgetch\fR, \fBmvgetch\fR and \fBmvwgetch\fR, routines read
64 a character from the window.
65 In no-delay mode, if no input is waiting, the value \fBERR\fR is returned.
66 In delay mode, the program waits until the system
67 passes text through to the program.
68 Depending on the setting of \fBcbreak\fR,
69 this is after one character (cbreak mode),
70 or after the first newline (nocbreak mode).
71 In half-delay mode,
72 the program waits until a character is typed or the
73 specified timeout has been reached.
74 .PP
75 If \fBecho\fR is enabled, and the window is not a pad,
76 then the character will also be echoed into the
77 designated window according to the following rules:
78 .bP
79 If the character is the current erase character, left arrow, or backspace,
80 the cursor is moved one space to the left and that screen position is erased
81 as if \fBdelch\fR had been called.
82 .bP
83 If the character value is any other \fBKEY_\fR define, the user is alerted
84 with a \fBbeep\fR call.
85 .bP
86 If the character is a carriage-return,
87 and if \fBnl\fP is enabled,
88 it is translated to a line-feed after echoing.
89 .bP
90 Otherwise the character is simply output to the screen.
91 .PP
92 If the window is not a pad, and it has been moved or modified since the last
93 call to \fBwrefresh\fR, \fBwrefresh\fR will be called before another character
94 is read.
95 .SS Keypad mode
96 .PP
97 If \fBkeypad\fR is \fBTRUE\fR, and a function key is pressed, the token for
98 that function key is returned instead of the raw characters:
99 .bP
100 The predefined function
101 keys are listed in \fB<curses.h>\fR as macros with values outside the range
102 of 8-bit characters.
103 Their names begin with \fBKEY_\fR.
104 .bP
105 Other (user-defined) function keys which may be defined using \fBdefine_key\fP(3X)
106 have no names, but also are expected to have values outside the range of
107 8-bit characters.
108 .PP
109 Thus, a variable
110 intended to hold the return value of a function key must be of short size or
111 larger.
112 .PP
113 When a character that could be the beginning of a function key is received
114 (which, on modern terminals, means an escape character),
115 \fBcurses\fR sets a timer.
116 If the remainder of the sequence does not come in within the designated
117 time, the character is passed through;
118 otherwise, the function key value is returned.
119 For this reason, many terminals experience a delay between the time
120 a user presses the escape key and the escape is returned to the program.
121 .PP
122 In \fBncurses\fP, the timer normally expires after the value in \fBESCDELAY\fP (see \fBcurs_variables\fP(3X)).
123 If \fBnotimeout\fP is \fBTRUE\fP, the timer does not expire;
124 it is an infinite (or very large) value.
125 Because function keys usually begin with an escape character,
126 the terminal may appear to hang in notimeout mode after pressing the escape key
127 until another key is pressed.
128 .SS Ungetting characters
129 .PP
130 The \fBungetch\fR routine places \fIch\fR back onto the input queue to be
131 returned by the next call to \fBwgetch\fR.
132 There is just one input queue for all windows.
133 .PP
134 .SS Predefined key-codes
135 The following special keys are defined in \fB<curses.h>\fR.
136 .bP
137 Except for the special case \fBKEY_RESIZE\fP,
138 it is necessary to enable \fBkeypad\fR for \fBgetch\fP to return these codes.
139 .bP
140 Not all of these are necessarily supported on any particular terminal.
141 .bP
142 The naming convention may seem obscure, with some apparent
143 misspellings (such as "RSUME" for "resume").
144 The names correspond to the long terminfo capability names for the keys,
145 and were defined long ago, in the 1980s.
146 .PP
147 .TS
148 center tab(/) ;
149 l l .
150 \fIName\fR/\fIKey\fR \fIname\fR
151 _
152 KEY_BREAK/Break key
153 KEY_DOWN/The four arrow keys ...
154 KEY_UP
155 KEY_LEFT
156 KEY_RIGHT
157 KEY_HOME/Home key (upward+left arrow)
158 KEY_BACKSPACE/Backspace
159 KEY_F0/T{
160 Function keys; space for 64 keys is reserved.
161 T}
162 KEY_F(\fIn\fR)/T{
163 For 0 \(<= \fIn\fR \(<= 63
164 T}
165 KEY_DL/Delete line
166 KEY_IL/Insert line
167 KEY_DC/Delete character
168 KEY_IC/Insert char or enter insert mode
169 KEY_EIC/Exit insert char mode
170 KEY_CLEAR/Clear screen
171 KEY_EOS/Clear to end of screen
172 KEY_EOL/Clear to end of line
173 KEY_SF/Scroll 1 line forward
174 KEY_SR/Scroll 1 line backward (reverse)
175 KEY_NPAGE/Next page
176 KEY_PPAGE/Previous page
177 KEY_STAB/Set tab
178 KEY_CTAB/Clear tab
179 KEY_CATAB/Clear all tabs
180 KEY_ENTER/Enter or send
181 KEY_SRESET/Soft (partial) reset
182 KEY_RESET/Reset or hard reset
183 KEY_PRINT/Print or copy
184 KEY_LL/Home down or bottom (lower left)
185 KEY_A1/Upper left of keypad
186 KEY_A3/Upper right of keypad
187 KEY_B2/Center of keypad
188 KEY_C1/Lower left of keypad
189 KEY_C3/Lower right of keypad
190 KEY_BTAB/Back tab key
191 KEY_BEG/Beg(inning) key
192 KEY_CANCEL/Cancel key
193 KEY_CLOSE/Close key
194 KEY_COMMAND/Cmd (command) key
195 KEY_COPY/Copy key
196 KEY_CREATE/Create key
197 KEY_END/End key
198 KEY_EXIT/Exit key
199 KEY_FIND/Find key
200 KEY_HELP/Help key
201 KEY_MARK/Mark key
202 KEY_MESSAGE/Message key
203 KEY_MOUSE/Mouse event read
204 KEY_MOVE/Move key
205 KEY_NEXT/Next object key
206 KEY_OPEN/Open key
207 KEY_OPTIONS/Options key
208 KEY_PREVIOUS/Previous object key
209 KEY_REDO/Redo key
210 KEY_REFERENCE/Ref(erence) key
211 KEY_REFRESH/Refresh key
212 KEY_REPLACE/Replace key
213 KEY_RESIZE/Screen resized
214 KEY_RESTART/Restart key
215 KEY_RESUME/Resume key
216 KEY_SAVE/Save key
217 KEY_SBEG/Shifted beginning key
218 KEY_SCANCEL/Shifted cancel key
219 KEY_SCOMMAND/Shifted command key
220 KEY_SCOPY/Shifted copy key
221 KEY_SCREATE/Shifted create key
222 KEY_SDC/Shifted delete char key
223 KEY_SDL/Shifted delete line key
224 KEY_SELECT/Select key
225 KEY_SEND/Shifted end key
226 KEY_SEOL/Shifted clear line key
227 KEY_SEXIT/Shifted exit key
228 KEY_SFIND/Shifted find key
229 KEY_SHELP/Shifted help key
230 KEY_SHOME/Shifted home key
231 KEY_SIC/Shifted input key
232 KEY_SLEFT/Shifted left arrow key
233 KEY_SMESSAGE/Shifted message key
234 KEY_SMOVE/Shifted move key
235 KEY_SNEXT/Shifted next key
236 KEY_SOPTIONS/Shifted options key
237 KEY_SPREVIOUS/Shifted prev key
238 KEY_SPRINT/Shifted print key
239 KEY_SREDO/Shifted redo key
240 KEY_SREPLACE/Shifted replace key
241 KEY_SRIGHT/Shifted right arrow
242 KEY_SRSUME/Shifted resume key
243 KEY_SSAVE/Shifted save key
244 KEY_SSUSPEND/Shifted suspend key
245 KEY_SUNDO/Shifted undo key
246 KEY_SUSPEND/Suspend key
247 KEY_UNDO/Undo key
248 .TE
249 .PP
250 Keypad is arranged like this:
251 .br
252 .TS
253 center allbox tab(/) ;
254 c c c .
255 \fBA1\fR/\fBup\fR/\fBA3\fR
256 \fBleft\fR/\fBB2\fR/\fBright\fR
257 \fBC1\fR/\fBdown\fR/\fBC3\fR
258 .TE
259 .sp
260 A few of these predefined values do \fInot\fP correspond to a real key:
261 .bP
262 .B KEY_RESIZE
263 is returned when the \fBSIGWINCH\fP signal has been detected
264 (see \fBinitscr\fP(3X) and \fBresizeterm\fR(3X)).
265 This code is returned whether or not \fBkeypad\fP has been enabled.
266 .bP
267 .B KEY_MOUSE
268 is returned for mouse-events (see \fBcurs_mouse\fR(3X)).
269 This code relies upon whether or not \fBkeypad\fP(3X) has been enabled,
270 because (e.g., with \fIxterm\fP mouse prototocol) ncurses must
271 read escape sequences,
272 just like a function key.
273 .SS Testing key-codes
274 .PP
275 The \fBhas_key\fR routine takes a key-code value from the above list, and
276 returns \fBTRUE\fP or \fBFALSE\fP according to whether
277 the current terminal type recognizes a key with that value.
278 .PP
279 The library also supports these extensions:
280 .RS 3
281 .TP 5
282 .B define_key
283 defines a key-code for a given string (see \fBdefine_key\fP(3X)).
284 .TP 5
285 .B key_defined
286 checks if there is a key-code defined for a given
287 string (see \fBkey_defined\fP(3X)).
288 .RE
289 .PP
290 .SH RETURN VALUE
291 All routines return the integer \fBERR\fR upon failure and an integer value
292 other than \fBERR\fR (\fBOK\fR in the case of \fBungetch\fP) upon successful
293 completion.
294 .RS 3
295 .TP 5
296 \fBungetch\fP
297 returns ERR
298 if there is no more room in the FIFO.
299 .TP
300 \fBwgetch\fP
301 returns ERR
302 if the window pointer is null, or
303 if its timeout expires without having any data, or
304 if the execution was interrupted by a signal (\fBerrno\fR will be set to
305 \fBEINTR\fR).
306 .RE
307 .PP
308 Functions with a "mv" prefix first perform a cursor movement using
309 \fBwmove\fP, and return an error if the position is outside the window,
310 or if the window pointer is null.
311 .SH NOTES
312 Use of the escape key by a programmer for a single character function is
313 discouraged, as it will cause a delay of up to one second while the
314 keypad code looks for a following function-key sequence.
315 .PP
316 Some keys may be the same as commonly used control
317 keys, e.g., \fBKEY_ENTER\fP versus control/M, \fBKEY_BACKSPACE\fP versus control/H.
318 Some curses implementations may differ according to whether they
319 treat these control keys specially (and ignore the terminfo), or
320 use the terminfo definitions.
321 \fBNcurses\fR uses the terminfo definition.
322 If it says that \fBKEY_ENTER\fP is control/M,
323 \fBgetch\fR will return \fBKEY_ENTER\fP
324 when you press control/M.
325 .PP
326 Generally, \fBKEY_ENTER\fP denotes the character(s) sent by the \fIEnter\fP
327 key on the numeric keypad:
328 .bP
329 the terminal description lists the most useful keys,
330 .bP
331 the \fIEnter\fP key on the regular keyboard is already handled by
332 the standard ASCII characters for carriage-return and line-feed,
333 .bP
334 depending on whether \fBnl\fP or \fBnonl\fP was called,
335 pressing "Enter" on the regular keyboard may return either a carriage-return
336 or line-feed, and finally
337 .bP
338 "Enter or send" is the standard description for this key.
339 .PP
340 When using \fBgetch\fR, \fBwgetch\fR, \fBmvgetch\fR, or
341 \fBmvwgetch\fR, nocbreak mode (\fBnocbreak\fR) and echo mode
342 (\fBecho\fR) should not be used at the same time.
343 Depending on the
344 state of the tty driver when each character is typed, the program may
345 produce undesirable results.
346 .PP
347 Note that \fBgetch\fR, \fBmvgetch\fR, and \fBmvwgetch\fR may be macros.
348 .PP
349 Historically, the set of keypad macros was largely defined by the extremely
350 function-key-rich keyboard of the AT&T 7300, aka 3B1, aka Safari 4.
351 Modern
352 personal computers usually have only a small subset of these.
353 IBM PC-style
354 consoles typically support little more than \fBKEY_UP\fR, \fBKEY_DOWN\fR,
355 \fBKEY_LEFT\fR, \fBKEY_RIGHT\fR, \fBKEY_HOME\fR, \fBKEY_END\fR,
356 \fBKEY_NPAGE\fR, \fBKEY_PPAGE\fR, and function keys 1 through 12.
357 The Ins key
358 is usually mapped to \fBKEY_IC\fR.
359 .SH PORTABILITY
360 The *get* functions are described in the XSI Curses standard, Issue 4.
361 They
362 read single-byte characters only.
363 The standard specifies that they return
364 \fBERR\fR on failure, but specifies no error conditions.
365 .PP
366 The echo behavior of these functions on input of \fBKEY_\fR or backspace
367 characters was not specified in the SVr4 documentation.
368 This description is
369 adopted from the XSI Curses standard.
370 .PP
371 The behavior of \fBgetch\fR and friends in the presence of handled signals is
372 unspecified in the SVr4 and XSI Curses documentation.
373 Under historical curses
374 implementations, it varied depending on whether the operating system's
375 implementation of handled signal receipt interrupts a \fBread\fR(2) call in
376 progress or not, and also (in some implementations) depending on whether an
377 input timeout or non-blocking mode has been set.
378 .PP
379 \fBKEY_MOUSE\fP is mentioned in XSI Curses, along with a few related
380 terminfo capabilities, but no higher-level functions use the feature.
381 The implementation in ncurses is an extension.
382 .PP
383 \fBKEY_RESIZE\fP is an extension first implemented for ncurses.
384 NetBSD curses later added this extension.
385 .PP
386 Programmers concerned about portability should be prepared for either of two
387 cases: (a) signal receipt does not interrupt \fBgetch\fR; (b) signal receipt
388 interrupts \fBgetch\fR and causes it to return ERR with \fBerrno\fR set to
389 \fBEINTR\fR.
390 .PP
391 The \fBhas_key\fR function is unique to \fBncurses\fR.
392 We recommend that
393 any code using it be conditionalized on the \fBNCURSES_VERSION\fR feature macro.
394 .SH SEE ALSO
395 \fBcurses\fR(3X),
396 \fBcurs_inopts\fR(3X),
397 \fBcurs_outopts\fR(3X),
398 \fBcurs_mouse\fR(3X),
399 \fBcurs_move\fR(3X),
400 \fBcurs_refresh\fR(3X),
401 \fBcurs_variables\fR(3X),
402 \fBresizeterm\fR(3X).
403 .PP
404 Comparable functions in the wide-character (ncursesw) library are
405 described in
406 \fBcurs_get_wch\fR(3X).