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1.1 root 1:
2:
3: termio Device Driver termio
4:
5:
6:
7:
8: General terminal interface
9:
10:
11: Under the COHERENT system, all asynchronous ports use the same
12: interface, no matter what hardware is involved. The remainder of
13: this section discusses the common features of this interface.
14:
15: When a terminal file is opened, it normally causes the process to
16: wait until a connection is established. In practice, users'
17: programs seldom open these files; they are opened by the program
18: getty and become a user's standard input, output, and error
19: files. The very first terminal file opened by the process group
20: leader of a terminal file not already associated with a process
21: group becomes the control terminal for that process group. The
22: control terminal plays a special role in handling quit and inter-
23: rupt signals, as discussed below. The control terminal is in-
24: herited by a child process during a call to fork. A process can
25: break this association by changing its process group using
26: setpgrp.
27:
28: A terminal associated with one of these files ordinarily operates
29: in full-duplex mode. Characters can be typed at any time, even
30: while output is occurring, and are only lost when the system's
31: input buffers become completely full, which is rare, or when the
32: user has accumulated the maximum allowed number of input charac-
33: ters that have not yet been read by some program. Currently,
34: this limit is 256 characters. When the input limit is reached,
35: the sytems throws away all the saved characters without notice.
36:
37: Normally, terminal input is processed in units of lines. A line
38: is delimited by a newline character (ASCII LF), an end-of-file
39: character (ASCII EOT), or an end-of-line character. This means
40: that a program attempting to read will be suspended until an en-
41: tire line has been typed. Also, no matter how many characters
42: are requested in the read call, at most one line will be
43: returned. It is not, however, necessary to read a whole line at
44: once; any number of characters may be requested in a read, even
45: one, without losing information.
46:
47: During input, the system normally processes erase and kill
48: characters. By default, the backspace character erases the last
49: character typed, except that it will not erase beyond the begin-
50: ning of the line. By default, the <ccttrrll-UU> calls (deletes) the
51: entire input line, and optionally outputs a newline character.
52: Both these characters operate on a keystroke-by-keystroke basis,
53: independently of any backspacing or tabbing which may have been
54: done. Both the erase and kill characters may be entered liter-
55: ally by preceding them with the escape character (\). In this
56: case, the escape character is not read. You may change the erase
57: and kill characters.
58:
59: Certain characters have special functions on input. These
60: functions and their default character values are summarized as
61: follows:
62:
63:
64: COHERENT Lexicon Page 1
65:
66:
67:
68:
69: termio Device Driver termio
70:
71:
72:
73:
74: IINNTTRR (<ccttrrll-CC> or ASCII ETX) generates an interrupt signal
75: that is sent to all processes with the associated con-
76: trol terminal. Normally, each such process is forced
77: to terminate, but arrangements may be made either to
78: ignore the signal or to receive a trap to an agreed-
79: upon location; see the Lexicon entry for signal.
80:
81: QQUUIITT (Control-\ or ASCII ES) generates a quit signal. Its
82: treatment is identical to that of the interrupt signal
83: except that, unless a receiving process has made other
84: arrangements, it will not only be terminated but a core
85: image file (called ccoorree) will be created in the current
86: working directory.
87:
88: EERRAASSEE (<bbaacckkssppaaccee> or ASCII BS) erases the preceding charac-
89: ter. It will not erase beyond the start of a line, as
90: delimited by a newline, EOF, or EOL character.
91:
92: KKIILLLL (<ccttrrll-UU> or ASCII NAK) deletes the entire line, as
93: delimited by a newline, EOF, or EOL character.
94:
95: EEOOFF (<ccttrrll-DD> or ASCII EOT) generates an end-of-file
96: character from a terminal. When received, all the
97: characters waiting to be read are immediately passed to
98: the program without waiting for a newline, and the EOF
99: is discarded. Thus, if no characters are waiting,
100: which is to say the EOF occurred at the beginning of a
101: line. zero characters will be passed back, which is
102: the standard end-of-file indication.
103:
104: NNLL (ASCII LF) is the normal line delimiter. It cannot be
105: changed or escaped.
106:
107: EEOOLL (ASCII LF) is an additional line delimiter, line NL.
108: It is not normally used.
109:
110: SSTTOOPP (<ccttrrll-SS> or ASCII DC3) can be used to suspend output.
111: It is useful with CRT terminals to prevent output from
112: disappearing before it can be read. While output is
113: suspended, STOP characters are ignored and not read.
114:
115: SSTTAARRTT (<ccttrrll-QQ> or ASCII DC1) resumes output that has been
116: suspended by a STOP character. While output is not
117: suspended, START characters are ignored and not read.
118: The start/stop characters can not be changed or es-
119: caped.
120:
121: The character values for INTR, QUIT, ERASE, KILL, EOF, and EOL
122: may be changed. to suit individual tastes. The ERASE, KILL, and
123: EOF character may be escaped by a preceding \ character, in which
124: case the system ignores its special meaning.
125:
126: When the carrier signal from the data-set drops, a hangup signal
127: is sent to all processes that have this terminal as the control
128:
129:
130: COHERENT Lexicon Page 2
131:
132:
133:
134:
135: termio Device Driver termio
136:
137:
138:
139: terminal. Unless other arrangements have been made, this signal
140: causes the process to terminate. If the hangup signal is ig-
141: nored, any subsequent read returns with an end-of-file indica-
142: tion. Thus programs that read a terminal and test for end-of-
143: file can terminate appropriately when hung up on.
144:
145: When one or more characters are written, they are transmitted to
146: the terminal as soon as previously written characters have
147: finished typing. Input characters are echoed by putting them
148: into the output queue as they arrive. If a process produces
149: characters more rapidly than they can be printed, it will be
150: suspended when its output queue exceeds some limit. When the
151: queue has drained down to some threshold, the program resumes.
152:
153: Several calls to ioctl apply to terminal files. The primary
154: calls use the following structure, defined in <tteerrmmiioo.hh>:
155:
156:
157: #define NCC 8
158: struct termio {
159: unsigned short c_iflag; /* input modes */
160: unsigned short c_oflag; /* output modes */
161: unsigned short c_cflag; /* control modes */
162: unsigned short c_lflag; /* local modes */
163: char c_line; /* line discipline */
164: unsigned char c_cc[NCC]; /* control chars */
165: };
166:
167:
168: The special control characters are defined by the array c_cc.
169: The relative positions and initial values for each function are
170: as follows:
171:
172:
173: 0 INTR ^C
174: 1 QUIT ^\
175: 2 ERASE \b
176: 3 KILL ^U
177: 4 EOF ^D
178: 5 EOL \n
179: 6 reserved
180: 7 reserved
181:
182:
183: The field c_iflag describes the basic terminal input control:
184:
185:
186: IGNBRK 0000001 Ignore break condition.
187: BRKINT 0000002 Signal interrupt on break.
188: IGNPAR 0000004 Ignore characters with parity errors.
189: PARMRK 0000010 Mark parity errors.
190: INPCK 0000020 Enable input parity check.
191: ISTRIP 0000040 Strip character.
192: INLCR 0000100 Map NL to CR on input.
193: IGNCR 0000200 Ignore CR.
194:
195:
196: COHERENT Lexicon Page 3
197:
198:
199:
200:
201: termio Device Driver termio
202:
203:
204:
205: ICRNL 0000400 Map CR to NL on input.
206: IUCLC 0001000 Map upper-case to lower-case on input.
207: IXON 0002000 Enable start/stop output control.
208: IXANY 0004000 Enable any character to restart output.
209: IXOFF 0010000 Enable start/stop input control.
210:
211:
212: If IGNBRK is set, the break condition (a character-framing error
213: with data all zeros) is ignored, that is, not put on the input
214: queue and therefore not read by any process. Otherwise, if
215: BRKINT is set, the break condition generates an interrupt signal
216: and flushes both the input and output queues. If IGNPAR is set,
217: characters with other framing and parity errors are ignored.
218:
219: If PARMRK is set, a character with a framing or parity error
220: which is not ignored is read as the three character sequence
221: 0377, 0, X, where X is the data of the character received in er-
222: ror. To avoid ambiguity in this case, if ISTRIP is not set, a
223: valid character of 0377 is read as 0377, 0377. If PARMRK is not
224: set, a framing or parity error which is not ignored is read as
225: the character NUL.
226:
227: If INPCK is set, input parity checking is enabled. If INPCK is
228: not set, input parity checking is disabled. This allows output
229: parity generation without input parity errors.
230:
231: If ISTRIP is set, valid input characters are stripped to 7-bits
232: before being processed; otherwise, all eight bits are processed.
233:
234: If INLCR is set, a received NL character is translated into a CR
235: character. If IGNCR is set, a received CR character is ignored
236: (not read). Otherwise if ICRNL is set, a received CR character
237: is translated into a NL character.
238:
239: If IUCLC is set, a received upper-case alphabetic character is
240: translated into the corresponding lower-case character.
241:
242: If IXON is set, start/stop output control is enabled. A received
243: STOP character will suspend output and a received START character
244: will restart output. All start/stop characters are ignored and
245: not read. If IXANY is set, any input character will restart out-
246: put which has been suspended.
247:
248: IF IXOFF is set, the system will transmit START/STOP characters
249: when the input queue is nearly empty/full.
250:
251: The initial input control value is all bits clear.
252:
253: The field c_oflag field specifies the system treatment of output:
254:
255: OPOST 0000001 Postprocess output.
256: OLCUC 0000002 Map lower case to upper on output.
257: ONLCR 0000004 Map NL to CR-NL on output.
258: OCRNL 0000010 Map CR to NL on output.
259: ONOCR 0000020 No CR output at column 0.
260:
261:
262: COHERENT Lexicon Page 4
263:
264:
265:
266:
267: termio Device Driver termio
268:
269:
270:
271: ONLRET 0000040 NL performs CR function.
272: OFILL 0000100 Use fill characters for delay.
273: OFDEL 0000200 Fill is DEL, else NUL.
274: NLDLY 0000400 Select new-line delays:
275: NL0 0
276: NL1 0000400
277: CRDLY 0003000 Select carriage-return delays:
278: CR0 0
279: CR1 0001000
280: CR2 0002000
281: CR3 0003000
282: TABDLY 0014000 Select horizontal-tab delays:
283: TAB0 0
284: TAB1 0004000
285: TAB2 0010000
286: TAB3 0014000 Expand tabs to spaces.
287: BSDLY 0020000 Select backspace delays:
288: BS0 0
289: BS1 0020000
290: VTDLY 0040000 Select vertical-tab delays:
291: VT0 0
292: VT1 0040000
293: FFDLY 0100000 Select form-feed delays:
294: FF0 0
295: FF1 0100000
296:
297: If OPOST is set, output characters are post-processed as in-
298: dicated by the remaining flags; otherwise, characters are trans-
299: mitted without change.
300:
301: If OLCUC is set, a lower-case alphabetic character is transmitted
302: as the corresponding upper-case character. This function is of-
303: ten used with IUCLC.
304:
305: If ONLCR is set, the NL character is transmitted as the CR-NL
306: character pair. If OCRNL is set, the CR character is transmitted
307: as the NL character. If ONOCR is set, no CR character is trans-
308: mitted when at column 0 (first position). If ONLRET is set, the
309: NL character is assumed to do the carriage-return function; the
310: column pointer is set to 0 and the delays specified for CR used.
311: Otherwise, the NL character is assumed to do just the line-feed
312: function; the column pointer remains unchanged. The column
313: pointer is also set to 0 if the CR character is actually trans-
314: mitted.
315:
316: The delay bits specify how long transmission stops to allow for
317: mechanical or other movement when certain characters are sent to
318: the terminal. In all cases, a value of 0 indicates no delay. If
319: OFILL is set, fill characters are transmitted for delay instead
320: of a timed delay. This is useful for high baud-rate terminals
321: that need only a minimal delay. If OFDEL is set, the fill
322: character is DEL; otherwise, it is NUL.
323:
324: If a form-feed or vertical-tab delay is specified, it lasts for
325: about two seconds.
326:
327:
328: COHERENT Lexicon Page 5
329:
330:
331:
332:
333: termio Device Driver termio
334:
335:
336:
337:
338: Newline delay lasts about 0.10 seconds. If ONLRET is set, the
339: carriage-return delays are used instead of the newline delays.
340: If OFILL is set, two fill characters are transmitted.
341:
342: Carriage-return delay type 1 is dependent on the current column
343: position, type 2 is about 0.10 seconds, and type 3 is about 0.15
344: seconds. If OFILL is set, delay type 1 transmits two fill
345: characters, and type 2 four fill characters.
346:
347: Horizontal-tab delay type 1 depends on the current column posi-
348: tion. Type 2 is about 0.10 seconds. Type 3 specifies that tabs
349: are to be expanded into spaces. If OFILL is set, two fill
350: characters are transmitted for any delay.
351:
352: Backspace delay lasts about 0.05 seconds. If OFILL is set, one
353: fill character is transmitted.
354:
355: The actual delays depend on line speed and system load.
356:
357: The initial output control value is all bits clear.
358:
359: The field c_cflag describes the hardware control of the terminal,
360: as follows:
361:
362: CBAUD 0000017 Baud rate:
363: B0 0 Hang up
364: B50 0000001 50 baud
365: B75 0000002 75 baud
366: B110 0000003 110 baud
367: B134 0000004 134.5 baud
368: B150 0000005 150 baud
369: B200 0000006 200 baud
370: B300 0000007 300 baud
371: B600 0000010 600 baud
372: B1200 0000011 1200 baud
373: B1800 0000012 1800 baud
374: B2400 0000013 2400 baud
375: B4800 0000014 4800 baud
376: B9600 0000015 9600 baud
377: B19200 0000016 19200 baud
378: B38400 0000017 38400 baud
379: CSIZE 0000060 Character size:
380: CS5 0 5 bits
381: CS6 0000020 6 bits
382: CS7 0000040 7 bits
383: CS8 0000060 8 bits
384: CSTOPB 0000100 Send two stop bits, else one
385: CREAD 0000200 Enable receiver
386: PARENB 0000400 Parity enable
387: PARODD 0001000 Odd parity, else even
388: HUPCL 0002000 Hang up on last close
389: CLOCAL 0004000 Local line, else dial-up
390:
391:
392:
393:
394: COHERENT Lexicon Page 6
395:
396:
397:
398:
399: termio Device Driver termio
400:
401:
402:
403: The CBAUD bits specify the baud rate. The zero baud rate, B0, is
404: used to hang up the connection. If B0 is specified, the data-
405: terminal-ready signal is not asserted. Normally, this discon-
406: nects the line. For any particular hardware, the system ignores
407: impossible changes to the speed.
408:
409: The CSIZE bits specify the character size in bits for both
410: transmission and reception. This size does not include the
411: parity bit, if any. If CSTOPB is set, two stop bits are used;
412: otherwise, one stop bit. For example, at 110 baud, two stop bits
413: are required.
414:
415: If PARENB is set, parity generation and detection is enabled and
416: a parity bit is added to each character. If parity is enabled,
417: the PARODD flag specifies odd parity if set; otherwise, even
418: parity is used.
419:
420: If CREAD is set, the receiver is enabled. Otherwise, no charac-
421: ters will be received.
422:
423: If HUPCL is set, COHERENT disconnects the line when the last
424: process with the line open closes the line or terminates; that
425: is, the data-terminal-ready signal is not asserted.
426:
427: If CLOCAL is set, the system assumes that the line to be a local,
428: direct connection with no modem control. Otherwise, it assumes
429: modem control.
430:
431: The initial hardware control value after open is B300, CS8,
432: CREAD, HUPCL.
433:
434: The line discipline uses the field c_lflag to control terminal
435: functions. The basic line discipline (0) provides the following:
436:
437:
438: ISIG 0000001 Enable signals.
439: ICANON 0000002 Canonical input (erase and kill processing).
440: XCASE 0000004 Canonical upper/lower presentation.
441: ECHO 0000010 Enable echo.
442: ECHOE 0000020 Echo erase character as BS-SP-BS.
443: ECHOK 0000040 Echo NL after kill character.
444: ECHONL 0000100 Echo NL.
445: NOFLSH 0000200 Disable flush after interrupt or quit.
446:
447:
448: If ISIG is set, the system checks each input character against
449: the special control characters INTR and QUIT. If an input
450: character matches one of these control characters, the system ex-
451: ecutes the function associated with that character. If ISIG is
452: not set, the system performs no checking; thus, these special in-
453: put functions are possible only if ISIG is set. You can disable
454: these functions individually by changing the value of the control
455: character to an unlikely or impossible value (e.g. 0377).
456:
457:
458:
459:
460: COHERENT Lexicon Page 7
461:
462:
463:
464:
465: termio Device Driver termio
466:
467:
468:
469: If ICANON is set, the system enables canonical processing. This
470: enables the erase and kill edit functions, and limits the as-
471: sembly of input characters into lines delimited by NL, EOF, and
472: EOL. If ICANON is not set, read requests are satisfied directly
473: from the input queue. A read will not be satisfied until at
474: least MIN characters have been received or the timeout value TIME
475: has expired. This allows the system to read efficiently fast
476: bursts of input while still allowing single-character input. The
477: MIN and TIME values are stored in the position for the EOF and
478: EOL characters, respectively. The time value represents tenths
479: of seconds.
480:
481: If XCASE is set, and if ICANON is set, an upper-case letter is
482: accepted on input by preceding it with a \ character, and is out-
483: put preceded by a \ character. In this mode, the following es-
484: cape sequences are generated on output and accepted on input:
485:
486:
487: _F_o_r: _U_s_e:
488:
489: ` \'
490: | \!
491: ~ \^
492: { \(
493: } \)
494: \ \\
495:
496:
497: For example, AA is input as \aa, \nn as \\nn, and \NN as \\\nn.
498:
499: If ECHO is set, characters are echoed as received.
500:
501: When ICANON is set, the following echo functions are possible: If
502: ECHO and ECHOE are set, the erase character is echoed as ASCII BS
503: SP BS, which clears the last character from the screen. If ECHOE
504: is set and EHO is not set, the erase character is echoed as ASCII
505: SP BS. If ECHOK is set, the NL character is echoed after the
506: kill character to emphasize that the line will be deleted. Note
507: that an escape character preceding the erase or kill character
508: removes any special function. If ECHONL is set, the NL character
509: is echoed even if ECHO is not set. This is useful for terminals
510: set to local echo (``half duplex''). Unless escaped, the EOF
511: character is not echoed. Because EOT is the default EOF charac-
512: ter, this prevents terminals that respond to EOT from hanging up.
513:
514: If NOFLSH is set, the normal flush of the input and output queues
515: associated with the quit and interrupt characters is not done.
516:
517: The initial line-discipline control value is all bits clear.
518:
519: The primary calls to ioctl have the following form:
520:
521:
522:
523:
524:
525:
526: COHERENT Lexicon Page 8
527:
528:
529:
530:
531: termio Device Driver termio
532:
533:
534:
535: ioctl( fildes, command, arg )
536: struct termio *arg;
537:
538:
539: The following commands use this form:
540:
541: TTCCGGEETTAA Get the parameters associated with the terminal and
542: store in the termio structure referenced by arg.
543:
544: TTCCSSEETTAA Set the parameters associated with the terminal from
545: the structure referenced by arg. The change is im-
546: mediate.
547:
548: TTCCSSEETTAAWW Wait for the output to drain before setting the new
549: parameters. This form should be used when changing
550: parameters that affect output.
551:
552: TTCCSSEETTAAFF Wait for the output to drain, then flush the input
553: queue and set the new parameters.
554:
555: Additional calls to ioctl have the following form:
556:
557:
558: ioctl( fildes, command, arg )
559: int arg;
560:
561:
562: The following commands use this form:
563:
564: TTCCSSBBRRKK Wait for the output to drain. If arg is zero, then
565: send a break (zero bits for 0.25 seconds).
566:
567: TTCCXXOONNCC Start/stop control. If arg is zero, suspend output; if
568: one, restart suspended output.
569:
570: TTCCFFLLSSHH If arg is zero, flush the input queue; if one, flush
571: the output queue; if two, flush both the input and out-
572: put queues.
573:
574: ***** Files *****
575:
576: /dev/tty*
577:
578: ***** See Also *****
579:
580: device drivers, ioctl(), stty, termio.h
581:
582:
583:
584:
585:
586:
587:
588:
589:
590:
591:
592: COHERENT Lexicon Page 9
593:
594:
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