1 TERMIO(7I) Ioctl Requests TERMIO(7I)
2
3 NAME
4 termio - general terminal interface
5
6 SYNOPSIS
7 #include <termio.h>
8
9 ioctl(int fildes, int request, struct termio *arg);
10
11 ioctl(int fildes, int request, int arg);
12
13 #include <termios.h>
14
15 ioctl(int fildes, int request, struct termios *arg);
16
17 DESCRIPTION
18 This release supports a general interface for asynchronous communications
19 ports that is hardware-independent. The user interface to this
20 functionality is using function calls (the preferred interface) described
21 in termios(3C) or ioctl() commands described in this section. This
22 section also discusses the common features of the terminal subsystem
23 which are relevant with both user interfaces.
24
25 When a terminal file is opened, it normally causes the process to wait
26 until a connection is established. In practice, user programs seldom
27 open terminal files; they are opened by the system and become a user's
28 standard input, output, and error files. The first terminal file opened
29 by the session leader that is not already associated with a session
30 becomes the controlling terminal for that session. The controlling
31 terminal plays a special role in handling quit and interrupt signals, as
32 discussed below. The controlling terminal is inherited by a child
33 process during a fork(2). A process can break this association by
34 changing its session using setsid(2).
35
36 A terminal associated with one of these files ordinarily operates in
37 full-duplex mode. Characters may be typed at any time, even while output
38 is occurring, and are only lost when the character input buffers of the
39 system become completely full, which is rare. For example, the number of
40 characters in the line discipline buffer may exceed {MAX_CANON} and
41 IMAXBEL (see below) is not set, or the user may accumulate {MAX_INPUT}
42 number of input characters that have not yet been read by some program.
43 When the input limit is reached, all the characters saved in the buffer
44 up to that point are thrown away without notice.
45
46 Session Management (Job Control)
47 A control terminal will distinguish one of the process groups in the
48 session associated with it to be the foreground process group. All other
49 process groups in the session are designated as background process
50 groups. This foreground process group plays a special role in handling
51 signal-generating input characters, as discussed below. By default, when
52 a controlling terminal is allocated, the controlling process's process
53 group is assigned as foreground process group.
54
55 Background process groups in the controlling process's session are
56 subject to a job control line discipline when they attempt to access
57 their controlling terminal. Process groups can be sent signals that will
58 cause them to stop, unless they have made other arrangements. An
59 exception is made for members of orphaned process groups.
60
61 An orphaned process group is one where the process group (see getpgid(2))
62 has no members with a parent in a different process group but sharing the
63 same controlling terminal. When a member of an orphaned process group
64 attempts to access its controlling terminal, EIO is returned because
65 there would be no way to restart the process if it were stopped on one of
66 these signals.
67
68 If a member of a background process group attempts to read its
69 controlling terminal, its process group will be sent a SIGTTIN signal,
70 which will normally cause the members of that process group to stop. If,
71 however, the process is ignoring or holding SIGTTIN, or is a member of an
72 orphaned process group, the read will fail with errno set to EIO, and no
73 signal is sent.
74
75 If a member of a background process group attempts to write its
76 controlling terminal and the TOSTOP bit is set in the c_lflag field, its
77 process group is sent a SIGTTOU signal, which will normally cause the
78 members of that process group to stop. If, however, the process is
79 ignoring or holding SIGTTOU, the write will succeed. If the process is
80 not ignoring or holding SIGTTOU and is a member of an orphaned process
81 group, the write will fail with errno set to EIO, and no signal will be
82 sent.
83
84 If TOSTOP is set and a member of a background process group attempts to
85 ioctl() its controlling terminal, and that ioctl() will modify terminal
86 parameters (for example, TCSETA, TCSETAW, TCSETAF, or TIOCSPGRP), its
87 process group will be sent a SIGTTOU signal, which will normally cause
88 the members of that process group to stop. If, however, the process is
89 ignoring or holding SIGTTOU, the ioctl will succeed. If the process is
90 not ignoring or holding SIGTTOU and is a member of an orphaned process
91 group, the write will fail with errno set to EIO, and no signal will be
92 sent.
93
94 Canonical Mode Input Processing
95 Normally, terminal input is processed in units of lines. A line is
96 delimited by a newline (ASCII LF) character, an end-of-file (ASCII EOT)
97 character, or an end-of-line character. This means that a program
98 attempting to read will block until an entire line has been typed. Also,
99 no matter how many characters are requested in the read call, at most one
100 line will be returned. It is not necessary, however, to read a whole
101 line at once; any number of characters may be requested in a read, even
102 one, without losing information.
103
104 During input, erase, erase2, and kill processing is normally done. The
105 ERASE and ERASE2 character (by default, the character DEL for ERASE and
106 Control-h for ERASE2) erases the last character typed. The WERASE
107 character (the character Control-w) erases the last "word" typed in the
108 current input line (but not any preceding spaces or tabs). A "word" is
109 defined as a sequence of non-blank characters, with tabs counted as
110 blanks. None of ERASE or ERASE2 or WERASE will erase beyond the
111 beginning of the line. The KILL character (by default, the character
112 NAK) kills (deletes) the entire input line, and optionally outputs a
113 newline character. All these characters operate on a key stroke basis,
114 independent of any backspacing or tabbing that may have been done. The
115 REPRINT character (the character Control-r) prints a newline followed by
116 all characters that have not been read. Reprinting also occurs
117 automatically if characters that would normally be erased from the screen
118 are fouled by program output. The characters are reprinted as if they
119 were being echoed; consequencely, if ECHO is not set, they are not
120 printed.
121
122 The ERASE, ERASE2, and KILL characters may be entered literally by
123 preceding them with the escape character. In this case, the escape
124 character is not read. The erase, erase2, and kill characters may be
125 changed.
126
127 Non-canonical Mode Input Processing
128 In non-canonical mode input processing, input characters are not
129 assembled into lines, and erase and kill processing does not occur. The
130 MIN and TIME values are used to determine how to process the characters
131 received.
132
133 MIN represents the minimum number of characters that should be received
134 when the read is satisfied (that is, when the characters are returned to
135 the user). TIME is a timer of 0.10-second granularity that is used to
136 timeout bursty and short-term data transmissions. The four possible
137 values for MIN and TIME and their interactions are described below.
138
139 Case A: MIN > 0, TIME > 0 In this case, TIME serves as an intercharacter
140 timer and is activated after the first
141 character is received. Since it is an
142 intercharacter timer, it is reset after a
143 character is received. The interaction
144 between MIN and TIME is as follows: as soon as
145 one character is received, the intercharacter
146 timer is started. If MIN characters are
147 received before the intercharacter timer
148 expires (note that the timer is reset upon
149 receipt of each character), the read is
150 satisfied. If the timer expires before MIN
151 characters are received, the characters
152 received to that point are returned to the
153 user. Note that if TIME expires, at least one
154 character will be returned because the timer
155 would not have been enabled unless a character
156 was received. In this case (MIN > 0, TIME >
157 0), the read sleeps until the MIN and TIME
158 mechanisms are activated by the receipt of the
159 first character. If the number of characters
160 read is less than the number of characters
161 available, the timer is not reactivated and
162 the subsequent read is satisfied immediately.
163
164 Case B: MIN > 0, TIME = 0 In this case, since the value of TIME is zero,
165 the timer plays no role and only MIN is
166 significant. A pending read is not satisfied
167 until MIN characters are received (the pending
168 read sleeps until MIN characters are
169 received). A program that uses this case to
170 read record based terminal I/O may block
171 indefinitely in the read operation.
172
173 Case C: MIN = 0, TIME > 0 In this case, since MIN 0, TIME no longer
174 represents an intercharacter timer: it now
175 serves as a read timer that is activated as
176 soon as a read(2) is done. A read is
177 satisfied as soon as a single character is
178 received or the read timer expires. Note
179 that, in this case, if the timer expires, no
180 character is returned. If the timer does not
181 expire, the only way the read can be satisfied
182 is if a character is received. In this case,
183 the read will not block indefinitely waiting
184 for a character; if no character is received
185 within TIME *.10 seconds after the read is
186 initiated, the read returns with zero
187 characters.
188
189 Case D: MIN = 0, TIME = 0 In this case, return is immediate. The
190 minimum of either the number of characters
191 requested or the number of characters
192 currently available is returned without
193 waiting for more characters to be input.
194
195 Comparing Different Cases of MIN, TIME Interaction
196 Some points to note about MIN and TIME:
197
198 o In the following explanations, note that the interactions of MIN
199 and TIME are not symmetric. For example, when MIN > 0 and TIME =
200 0, TIME has no effect. However, in the opposite case, where MIN =
201 0 and TIME > 0, both MIN and TIME play a role in that MIN is
202 satisfied with the receipt of a single character.
203
204 o Also note that in case A (MIN > 0, TIME > 0), TIME represents an
205 intercharacter timer, whereas in case C (MIN = 0, TIME > 0), TIME
206 represents a read timer.
207
208 These two points highlight the dual purpose of the MIN/TIME feature.
209 Cases A and B, where MIN > 0, exist to handle burst mode activity (for
210 example, file transfer programs), where a program would like to process
211 at least MIN characters at a time. In case A, the inteercharacter timer
212 is activated by a user as a safety measure; in case B, the timer is
213 turned off.
214
215 Cases C and D exist to handle single character, timed transfers. These
216 cases are readily adaptable to screen-based applications that need to
217 know if a character is present in the input queue before refreshing the
218 screen. In case C, the read is timed, whereas in case D, it is not.
219
220 Another important note is that MIN is always just a minimum. It does not
221 denote a record length. For example, if a program does a read of 20
222 bytes, MIN is 10, and 25 characters are present, then 20 characters will
223 be returned to the user.
224
225 Writing Characters
226 When one or more characters are written, they are transmitted to the
227 terminal as soon as previously written characters have finished typing.
228 nputt characters are echoed as they are typed if echoing has been
229 enabled. If a process produces characters more rapidly than they can be
230 typed, it will be suspended when its output queue exceeds some limit.
231 When the queue is drained down to some threshold, the program is resumed.
232
233 Special Characters
234 Certain characters have special functions on input. These functions and
235 their default character values are summarized as follows:
236
237 INTR (Control-c or ASCII ETX) generates a SIGINT signal. SIGINT is
238 sent to all foreground processes associated with the controlling
239 terminal. Normally, each such process is forced to terminate,
240 but arrangements may be made either to ignore the signal or to
241 receive a trap to an agreed upon location. (See
242 signal.h(3HEAD)).
243
244 QUIT (Control-| or ASCII FS) generates a SIGQUIT signal. Its
245 treatment is identical to the interrupt signal except that,
246 unless a receiving process has made other arrangements, it will
247 not only be terminated but a core image file (called core) will
248 be created in the current working directory.
249
250 ERASE (DEL) erases the preceding character. It does not erase beyond
251 the start of a line, as delimited by a NL, EOF, EOL, or EOL2
252 character.
253
254 ERASE2 (Control-h or ASCII BS) erases the preceding character, with
255 behaviour identical to that of ERASE.
256
257 WERASE (Control-w or ASCII ETX) erases the preceding "word". It does
258 not erase beyond the start of a line, as delimited by a NL, EOF,
259 EOL, or EOL2 character.
260
261 KILL (Control-u or ASCII NAK) deletes the entire line, as delimited
262 by a NL, EOF, EOL, or EOL2 character.
263
264 REPRINT (Control-r or ASCII DC2) reprints all characters, preceded by a
265 newline, that have not been read.
266
267 EOF (Control-d or ASCII EOT) may be used to generate an end-of-file
268 from a terminal. When received, all the characters waiting to
269 be read are immediately passed to the program, without waiting
270 for a newline, and the EOF is discarded. Thus, if no characters
271 are waiting (that is, the EOF occurred at the beginning of a
272 line) zero characters are passed back, which is the standard
273 end-of-file indication. Unless escaped, the EOF character is
274 not echoed. Because EOT is the default EOF character, this
275 prevents terminals that respond to EOT from hanging up.
276
277 NL (ASCII LF) is the normal line delimiter. It cannot be changed
278 or escaped.
279
280 EOL (ASCII NULL) is an additional line delimiter, like NL. It is
281 not normally used.
282
283 EOL2 is another additional line delimiter.
284
285 SWTCH (Control-z or ASCII EM) Header file symbols related to this
286 special character are present for compatibility purposes only
287 and the kernel takes no special action on matching SWTCH (except
288 to discard the character).
289
290 SUSP (Control-z or ASCII SUB) generates a SIGTSTP signal. SIGTSTP
291 stops all processes in the foreground process group for that
292 terminal.
293
294 DSUSP (Control-y or ASCII EM). It generates a SIGTSTP signal as SUSP
295 does, but the signal is sent when a process in the foreground
296 process group attempts to read the DSUSP character, rather than
297 when it is typed.
298
299 STOP (Control-s or ASCII DC3) can be used to suspend output
300 temporarily. It is useful with CRT terminals to prevent output
301 from disappearing before it can be read. While output is
302 suspended, STOP characters are ignored and not read.
303
304 START (Control-q or ASCII DC1) is used to resume output. Output has
305 been suspended by a STOP character. While output is not
306 suspended, START characters are ignored and not read.
307
308 DISCARD (Control-o or ASCII SI) causes subsequent output to be
309 discarded. Output is discarded until another DISCARD character
310 is typed, more input arrives, or the condition is cleared by a
311 program.
312
313 STATUS (Control-t or ASCII DC4) generates a SIGINFO signal. Processes
314 with a handler will output status information when they receive
315 SIGINFO, for example, dd(1M). If a process does not have a
316 SIGINFO handler, the signal will be ignored.
317
318 LNEXT (Control-v or ASCII SYN) causes the special meaning of the next
319 character to be ignored. This works for all the special
320 characters mentioned above. It allows characters to be input
321 that would otherwise be interpreted by the system (for example
322 KILL, QUIT). The character values for INTR, QUIT, ERASE,
323 ERASE2, WERASE, KILL, REPRINT, EOF, EOL, EOL2, SWTCH, SUSP,
324 DSUSP, STOP, START, DISCARD, STATUS, and LNEXT may be changed to
325 suit individual tastes. If the value of a special control
326 character is _POSIX_VDISABLE (0), the function of that special
327 control character is disabled. The ERASE, ERASE2, KILL, and EOF
328 characters may be escaped by a preceding backslash (\)
329 character, in which case no special function is done. Any of
330 the special characters may be preceded by the LNEXT character,
331 in which case no special function is done.
332
333 Modem Disconnect
334 When a modem disconnect is detected, a SIGHUP signal is sent to the
335 terminal's controlling process. Unless other arrangements have been
336 made, these signals cause the process to terminate. If SIGHUP is ignored
337 or caught, any subsequent read returns with an end-of-file indication
338 until the terminal is closed.
339
340 If the controlling process is not in the foreground process group of the
341 terminal, a SIGTSTP is sent to the terminal's foreground process group.
342 Unless other arrangements have been made, these signals cause the
343 processes to stop.
344
345 Processes in background process groups that attempt to access the
346 controlling terminal after modem disconnect while the terminal is still
347 allocated to the session will receive appropriate SIGTTOU and SIGTTIN
348 signals. Unless other arrangements have been made, this signal causes
349 the processes to stop.
350
351 The controlling terminal will remain in this state until it is
352 reinitialized ithh a successful open by the controlling process, or
353 deallocated by the controlling process.
354
355 Terminal Parameters
356 The parameters that control the behavior of devices and modules providing
357 the termios interface are specified by the termios structure defined by
358 <termios.h>. Several ioctl(2) system calls that fetch or change these
359 parameters use this structure that contains the following members:
360
361 tcflag_t c_iflag; /* input modes */
362 tcflag_t c_oflag; /* output modes */
363 tcflag_t c_cflag; /* control modes */
364 tcflag_t c_lflag; /* local modes */
365 cc_t c_cc[NCCS]; /* control chars */
366
367 The special control characters are defined by the array c_cc. The
368 symbolic name NCCS is the size of the Control-character array and is also
369 defined by <termios.h>. The relative positions, subscript names, and
370 typical default values for each function are as follows:
371
372 Relative Position Subscript Name Typical Default Value
373 0 VINTR ETX
374 1 VQUIT FS
375 2 VERASE DEL
376 3 VKILL NAK
377 4 VEOF EOT
378 5 VEOL NUL
379 6 VEOL2 NUL
380 7 VWSTCH NUL
381 8 VSTART NUL
382 9 VSTOP DC3
383 10 VSUSP SUB
384 11 VDSUSP EM
385 12 VREPRINT DC2
386 13 VDISCARD SI
387 14 VWERASE ETB
388 15 VLNEXT SYN
389 16 VSTATUS DC4
390 17 VERASE2 BS
391 18-19 Reserved
392
393 Input Modes
394 The c_iflag field describes the basic terminal input control:
395
396 IGNBRK Ignore break condition.
397 BRKINT Signal interrupt on break.
398 IGNPAR Ignore characters with parity errors.
399 PARMRK Mark parity errors.
400 INPCK Enable input parity check.
401 ISTRIP Strip character.
402 INLCR Map NL to CR on input.
403 IGNCR Ignore CR.
404 ICRNL Map CR to NL on input.
405 IUCLC Map upper-case to lower-case on input.
406 IXON Enable start/stop output control.
407 IXANY Enable any character to restart output.
408 IXOFF Enable start/stop input control.
409 IMAXBEL Echo BEL on input line too long.
410
411 If IGNBRK is set, a break condition (a character framing error with data
412 all zeros) detected on input is ignored, that is, not put on the input
413 queue and therefore not read by any process. If IGNBRK is not set and
414 BRKINT is set, the break condition shall flush the input and output
415 queues and if the terminal is the controlling terminal of a foreground
416 process group, the break condition generates a single SIGINT signal to
417 that foreground process group. If neither IGNBRK nor BRKINT is set, a
418 break condition is read as a single `\0' (ASCII NULL) character, or if
419 PARMRK is set, as `\377', `\0', c, where `\377' is a single character
420 with value 377 octal (0xff hex, 255 decimal), `\0' is a single character
421 with value 0, and c is the errored character received.
422
423 If IGNPAR is set, a byte with framing or parity errors (other than break)
424 is ignored.
425
426 If PARMRK is set, and IGNPAR is not set, a byte with a framing or parity
427 error (other than break) is given to the application as the three-
428 character sequence: `\377', `\0', c, where `\377' is a single character
429 with value 377 octal (0xff hex, 255 decimal), `\0' is a single character
430 with value 0, and c is the errored character received. To avoid
431 ambiguity in this case, if ISTRIP is not set, a valid character of `\377'
432 is given to the application as `\377'. If neither IGNPAR nor PARMRK is
433 set, a framing or parity error (other than break) is given to the
434 application as a single `\0' (ASCII NULL) character.
435
436 If INPCK is set, input parity checking is enabled. If INPCK is not set,
437 input parity checking is disabled. This allows output parity generation
438 without input parity errors. Note that whether input parity checking is
439 enabled or disabled is independent of whether parity detection is enabled
440 or disabled. If parity detection is enabled but input parity checking is
441 disabled, the hardware to which the terminal is connected will recognize
442 the parity bit, but the terminal special file will not check whether this
443 is set correctly or not.
444
445 If ISTRIP is set, valid input characters are first stripped to seven
446 bits, otherwise all eight bits are processed.
447
448 If INLCR is set, a received NL character is translated into a CR
449 character. If IGNCR is set, a received CR character is ignored (not
450 read). Otherwise, if ICRNL is set, a received CR character is translated
451 into a NL character.
452
453 If IUCLC is set, a received upper case, alphabetic character is
454 translated into the corresponding lower case character.
455
456 If IXON is set, start/stop output control is enabled. A received STOP
457 character suspends output and a received START character restarts output.
458 The STOP and START characters will not be read, but will merely perform
459 flow control functions. If IXANY is set, any input character restarts
460 output that has been suspended.
461
462 If IXOFF is set, the system transmits a STOP character when the input
463 queue is nearly full, and a START character when enough input has been
464 read so that the input queue is nearly empty again.
465
466 If IMAXBEL is set, the ASCII BEL character is echoed if the input stream
467 overflows. Further input is not stored, but any input already present in
468 the input stream is not disturbed. If IMAXBEL is not set, no BEL
469 character is echoed, and all input present in the input queue is
470 discarded if the input stream overflows.
471
472 Output Modes
473 The c_oflag field specifies the system treatment of output:
474
475 OPOST Post-process output.
476 OLCUC Map lower case to upper on output.
477 ONLCR Map NL to CR-NL on output.
478 OCRNL Map CR to NL on output.
479 ONOCR No CR output at column 0.
480 ONLRET NL performs CR function.
481 OFILL Use fill characters for delay.
482 OFDEL Fill is DEL, else INULL.
483 NLDLY Select newline delays:
484 NL0
485 NL1
486 CRDLY Select carriage-return delays:
487 CR0
488 CR1
489 CR2
490 CR3
491 TABDLY Select horizontal tab delays or tab expansion:
492 TAB0
493 TAB1
494 TAB2
495 TAB3 Expand tabs to spaces
496 XTABS Expand tabs to spaces
497 BSDLY Select backspace delays:
498 BS0
499 BS1
500 VTDLY Select vertical tab delays:
501 VT0
502 VT1
503 FFDLY Select form feed delays:
504 FF0
505 FF1
506
507 If OPOST is set, output characters are post-processed as indicated by the
508 remaining flags; otherwise, characters are transmitted without change.
509
510 If OLCUC is set, a lower case alphabetic character is transmitted as the
511 corresponding upper case character. This function is often used in
512 conjunction with IUCLC.
513
514 If ONLCR is set, the NL character is transmitted as the CR-NL character
515 pair. If OCRNL is set, the CR character is transmitted as the NL
516 character. If ONOCR is set, no CR character is transmitted when at
517 column 0 (first position). If ONRET is set, the NL character is assumed
518 to do the carriage-return function; the column pointer is set to 0 and
519 the delays specified for CR are used. Otherwise, the NL character is
520 assumed to do just the line-feed function; the column pointer remains
521 unchanged. The column pointer is also set to 0 if the CR character is
522 actually transmitted.
523
524 The delay bits specify how long transmission stops to allow for
525 mechanical or other movement when certain characters are sent to the
526 terminal. In all cases, a value of 0 indicates no delay. If OFILL is
527 set, fill characters are transmitted for delay instead of a timed delay.
528 This is useful for high baud rate terminals that need only a minimal
529 delay. If OFDEL is set, the fill character is DEL; otherwise it is NULL.
530
531 If a form-feed or vertical-tab delay is specified, it lasts for about 2
532 seconds.
533
534 Newline delay lasts about 0.10 seconds. If ONLRET is set, the carriage-
535 return delays are used instead of the newline delays. If OFILL is set,
536 two fill characters are transmitted.
537
538 Carriage-return delay type 1 is dependent on the current column position,
539 type 2 is about 0.10 seconds, and type 3 is about 0.15 seconds. If OFILL
540 is set, delay type 1 transmits two fill characters, and type 2 transmits
541 four fill characters.
542
543 Horizontal-tab delay type 1 is dependent on the current column position.
544 Type 2 is about 0.10 seconds. Type 3 specifies that tabs are to be
545 expanded into spaces. If OFILL is set, two fill characters are
546 transmitted for any delay.
547
548 Backspace delay lasts about 0.05 seconds. If OFILL is set, one fill
549 character is transmitted.
550
551 The actual delays depend on line speed and system load.
552
553 Control Modes
554 The c_cflag field describes the hardware control of the terminal:
555
556 CBAUD Baud rate:
557 B0 Hang up
558 B50 50 baud
559 B75 75 baud
560 B110 110 baud
561 B134 134 baud
562 B150 150 baud
563 B200 200 baud
564 B300 300 baud
565 B600 600 baud
566 B1200 1200 baud
567 B1800 1800 baud
568 B2400 2400 baud
569 B4800 4800 baud
570 B9600 9600 baud
571 B19200 19200 baud
572 EXTA External A
573 B38400 38400 baud
574 EXTB External B
575 B57600 57600 baud
576 B76800 76800 baud
577 B115200 115200 baud
578 B153600 153600 baud
579 B230400 230400 baud
580 B307200 307200 baud
581 B460800 460800 baud
582
583 CSIZE Character size:
584 CS5 5 bits
585 CS6 6 bits
586 CS7 7 bits
587 CS8 8 bits
588 CSTOPB Send two stop bits, else one
589 CREAD Enable receiver
590 PARENB Parity enable
591 PARODD Odd parity, else even
592 HUPCL Hang up on last close
593 CLOCAL Local line, else dial-up
594 CIBAUD Input baud rate, if different from output rate
595 PAREXT Extended parity for mark and space parity
596 CRTSXOFF Enable inbound hardware flow control
597 CRTSCTS Enable outbound hardware flow control
598 CBAUDEXT Bit to indicate output speed > B38400
599 CIBAUDEXT Bit to indicate input speed > B38400
600
601 The CBAUD bits together with the CBAUDEXT bit specify the output baud
602 rate. To retrieve the output speed from the termios structure pointed to
603 by termios_p see the following code segment.
604
605 speed_t ospeed;
606 if (termios_p->c_cflag & CBAUDEXT)
607 ospeed = (termios_p->c_cflag & CBAUD) + CBAUD + 1;
608 else
609 ospeed = termios_p->c_cflag & CBAUD;
610
611 To store the output speed in the termios structure pointed to by
612 termios_p see the following code segment.
613
614 speed_t ospeed;
615 if (ospeed > CBAUD) {
616 termios_p->c_cflag |= CBAUDEXT;
617 ospeed -= (CBAUD + 1);
618 } else {
619 termios_p->c_cflag &= ~CBAUDEXT;
620 }
621 termios_p->c_cflag =
622 (termios_p->c_cflag & ~CBAUD) | (ospeed & CBAUD);
623
624 The zero baud rate, B0, is used to hang up the connection. If B0 is
625 specified, the data-terminal-ready signal is not asserted. Normally,
626 this disconnects the line.
627
628 If the CIBAUDEXT or CIBAUD bits are not zero, they specify the input baud
629 rate, with the CBAUDEXT and CBAUD bits specifying the output baud rate;
630 otherwise, the output and input baud rates are both specified by the
631 CBAUDEXT and CBAUD bits. The values for the CIBAUD bits are the same as
632 the values for the CBAUD bits, shifted left IBSHIFT bits. For any
633 particular hardware, impossible speed changes are ignored. To retrieve
634 the input speed in the termios structure pointed to by termios_p see the
635 following code segment.
636
637 speed_t ispeed;
638 if (termios_p->c_cflag & CIBAUDEXT) {
639 ispeed = ((termios_p->c_cflag & CIBAUD) >> IBSHIFT)
640 + (CIBAUD >> IBSHIFT) + 1;
641 } else {
642 ispeed = (termios_p->c_cflag & CIBAUD) >> IBSHIFT;
643 }
644
645 To store the input speed in the termios structure pointed to by termios_p
646 see the following code segment.
647
648 speed_t ispeed;
649 if (ispeed == 0) {
650 ispeed = termios_p->c_cflag & CBAUD;
651 if (termios_p->c_cflag & CBAUDEXT)
652 ispeed += (CBAUD + 1);
653 }
654 if ((ispeed << IBSHIFT) > CIBAUD) {
655 termios_p->c_cflag |= CIBAUDEXT;
656 ispeed -= ((CIBAUD >> IBSHIFT) + 1);
657 } else {
658 termios_p->c_cflag &= ~CIBAUDEXT;
659 }
660 termios_p->c_cflag =
661 (termios_p->c_cflag & ~CIBAUD) | ((ispeed << IBSHIFT) & CIBAUD);
662
663 The CSIZE bits specify the character size in bits for both transmission
664 and reception. This size does not include the parity bit, if any. If
665 CSTOPB is set, two stop bits are used; otherwise, one stop bit is used.
666 For example, at 110 baud, two stops bits are required.
667
668 If PARENB is set, parity generation and detection is enabled, and a
669 parity bit is added to each character. If parity is enabled, the PARODD
670 flag specifies odd parity if set; otherwise, even parity is used.
671
672 If CREAD is set, the receiver is enabled. Otherwise, no characters are
673 received.
674
675 If HUPCL is set, the line is disconnected when the last process with the
676 line open closes it or terminates. That is, the data-terminal-ready
677 signal is not asserted.
678
679 If CLOCAL is set, the line is assumed to be a local, direct connection
680 with no modem control; otherwise, modem control is assumed.
681
682 If CRTSXOFF is set, inbound hardware flow control is enabled.
683
684 If CRTSCTS is set, outbound hardware flow control is enabled.
685
686 The four possible combinations for the state of CRTSCTS and CRTSXOFF bits
687 and their interactions are described below.
688
689 Case A: CRTSCTS off, CRTSXOFF off. In this case the hardware flow
690 control is disabled.
691
692 Case B: CRTSCTS on, CRTSXOFF off. In this case only outbound hardware
693 flow control is enabled. The state of CTS signal is used to do
694 outbound flow control. It is expected that output will be
695 suspended if CTS is low and resumed when CTS is high.
696
697 Case C: CRTSCTS off, CRTSXOFF on. In this case only inbound hardware
698 flow control is enabled. The state of RTS signal is used to do
699 inbound flow control. It is expected that input will be
700 suspended if RTS is low and resumed when RTS is high.
701
702 Case D: CRTSCTS on, CRTSXOFF on. In this case both inbound and outbound
703 hardware flow control are enabled. Uses the state of CTS signal
704 to do outbound flow control and RTS signal to do inbound flow
705 control.
706
707 Local Modes
708 The c_lflag field of the argument structure is used by the line
709 discipline to control terminal functions. The basic line discipline
710 provides the following:
711
712 ISIG Enable signals.
713 ICANON Canonical input (erase and kill processing).
714 XCASE Canonical upper/lower presentation.
715 ECHO Enable echo.
716 ECHOE Echo erase character as BS-SP-BS &.
717 ECHOK Echo NL after kill character.
718 ECHONL Echo NL.
719 NOFLSH Disable flush after interrupt or quit.
720 TOSTOP Send
721 SIGTTOU for background output.
722 ECHOCTL Echo control characters as char, delete as ^?.
723 ECHOPRT Echo erase character as character erased.
724 ECHOKE BS-SP-BS erase entire line on line kill.
725 FLUSHO Output is being flushed.
726 PENDIN Retype pending input at next read or input character.
727 IEXTEN Enable extended (implementation-defined) functions.
728
729 If ISIG is set, each input character is checked against the special
730 control characters INTR, QUIT, SWTCH, SUSP, STATUS, and DSUSP. If an
731 input character matches one of these control characters, the function
732 associated with that character is performed. (Note: If SWTCH is set and
733 the character matches, the character is simply discarded. No other
734 action is taken.) If ISIG is not set, no checking is done. Thus, these
735 special input functions are possible only if ISIG is set.
736
737 If ICANON is set, canonical processing is enabled. This enables the
738 erase and kill edit functions, and the assembly of input characters into
739 lines delimited by NL-c, EOF, EOL, and EOL. If ICANON is not set, read
740 requests are satisfied directly from the input queue. A read is not
741 satisfied until at least MIN characters have been received or the timeout
742 value TIME has expired between characters. This allows fast bursts of
743 input to be read efficiently while still allowing single character input.
744 The time value represents tenths of seconds.
745
746 If XCASE is set and ICANON is set, an upper case letter is accepted on
747 input if preceded by a backslash `\' character, and is output preceded by
748 a backslash `\' character. In this mode, the following escape sequences
749 are generated on output and accepted on input:
750
751 FOR: USE:
752 ` \'
753 | \!
754 ~ \^
755 { \(
756 } \)
757 \ \\
758
759 For example, input A as \a, \n as \\n, and \N as \\\n.
760
761 If ECHO is set, characters are echoed as received.
762
763 When ICANON is set, the following echo functions are possible.
764
765 o If ECHO and ECHOE are set, and ECHOPRT is not set, the ERASE,
766 ERASE2, and WERASE characters are echoed as one or more ASCII
767 BS SP BS, which clears the last character(s) from a CRT screen.
768
769 o If ECHO, ECHOPRT, and IEXTEN are set, the first ERASE, ERASE2,
770 and WERASE character in a sequence echoes as a backslash `\',
771 followed by the characters being erased. Subsequent ERASE and
772 WERASE characters echo the characters being erased, in reverse
773 order. The next non-erase character causes a `/' (slash) to be
774 typed before it is echoed. ECHOPRT should be used for hard
775 copy terminals.
776
777 o If ECHOKE and IEXTEN are set, the kill character is echoed by
778 erasing each character on the line from the screen (using the
779 mechanism selected by ECHOE and ECHOPR).
780
781 o If ECHOK is set, and ECHOKE is not set, the NL character is
782 echoed after the kill character to emphasize that the line is
783 deleted. Note that a `\' (escape) character or an LNEXT
784 character preceding the erase or kill character removes any
785 special function.
786
787 o If ECHONL is set, the NL character is echoed even if ECHO is
788 not set. This is useful for terminals set to local echo (so
789 called half-duplex).
790
791 If ECHOCTL and IEXTEN are set, all control characters (characters with
792 codes between 0 and 37 octal) other than ASCII TAB, ASCII NL, the START
793 character, and the STOP character, ASCII CR, and ASCII BS are echoed as
794 ^X, where X is the character given by adding `100' octal to the code of
795 the control character (so that the character with octal code `1' is
796 echoed as ^A), and the ASCII DEL character, with code `177' octal, is
797 echoed as ^?.
798
799 If NOFLSH is set, the normal flush of the input and output queues
800 associated with the INTR, QUIT, STATUS, and SUSP characters is not done.
801 This bit should be set when restarting system calls that read from or
802 write to a terminal (see sigaction(2)).
803
804 If TOSTOP and IEXTEN are set, the signal SIGTTOU is sent to a process
805 that tries to write to its controlling terminal if it is not in the
806 foreground process group for that terminal. This signal normally stops
807 the process. Otherwise, the output generated by that process is output
808 to the current output stream. Processes that are blocking or ignoring
809 SIGTTOU signals are excepted and allowed to produce output, if any.
810
811 If FLUSHO and IEXTEN are set, data written to the terminal is discarded.
812 This bit is set when the FLUSH character is typed. A program can cancel
813 the effect of typing the FLUSH character by clearing FLUSHO.
814
815 If PENDIN and IEXTEN are set, any input that has not yet been read is
816 reprinted when the next character arrives as input. PENDIN is then
817 automatically cleared.
818
819 If IEXTEN is set, the following implementation-defined functions are
820 enabled: special characters ( WERASE, REPRINT, DISCARD, and LNEXT) and
821 local flags ( TOSTOP, ECHOCTL, ECHOPRT, ECHOKE, FLUSHO, and PENDIN).
822
823 Minimum and Timeout
824 The MIN and TIME values were described previously, in the subsection,
825 Non-canonical Mode Input Processing. The initial value of MIN is 1, and
826 the initial value of TIME is 0.
827
828 Terminal Size
829 The number of lines and columns on the terminal's display is specified in
830 the winsize structure defined by <sys/termios.h> and includes the
831 following members:
832
833 unsigned short ws_row; /* rows, in characters */
834 unsigned short ws_col; /* columns, in characters */
835 unsigned short ws_xpixel; /* horizontal size, in pixels */
836 unsigned short ws_ypixel; /* vertical size, in pixels */
837
838 Termio Structure
839 The SunOS/SVR4 termio structure is used by some ioctl()s; it is defined
840 by <sys/termio.h> and includes the following members:
841
842 unsigned short c_iflag; /* input modes */
843 unsigned short c_oflag; /* output modes */
844 unsigned short c_cflag; /* control modes */
845 unsigned short c_lflag; /* local modes */
846 char c_line; /* line discipline */
847 unsigned char c_cc[NCC]; /* control chars */
848
849 The special control characters are defined by the array c_cc. The
850 symbolic name NCC is the size of the Control-character array and is also
851 defined by <termio.h>. The relative positions, subscript names, and
852 typical default values for each function are as follows:
853
854 Relative Positions Subscript Names Typical Default Values
855 0 VINTR EXT
856 1 VQUIT FS
857 2 VERASE DEL
858 3 VKILL NAK
859 4 VEOF EOT
860 5 VEOL NUL
861 6 VEOL2 NUL
862 7 Reserved
863
864 The MIN values is stored in the VMIN element of the c_cc array; the TIME
865 value is stored in the VTIME element of the c_cc array. The VMIN element
866 is the same element as the VEOF element; the VTIME element is the same
867 element as the VEOL element.
868
869 The calls that use the termio structure only affect the flags and control
870 characters that can be stored in the termio structure; all other flags
871 and control characters are unaffected.
872
873 Modem Lines
874 On special files representing serial ports, modem control lines can be
875 read. Control lines (if the underlying hardware supports it) may also be
876 changed. Status lines are read-only. The following modem control and
877 status lines may be supported by a device; they are defined by
878 <sys/termios.h>:
879
880 TIOCM_LE line enable
881 TIOCM_DTR data terminal ready
882 TIOCM_RTS request to send
883 TIOCM_ST secondary transmit
884 TIOCM_SR secondary receive
885 TIOCM_CTS clear to send
886 TIOCM_CAR carrier detect
887 TIOCM_RNG ring
888 TIOCM_DSR data set ready
889
890 TIOCM_CD is a synonym for TIOCM_CAR, and TIOCM_RI is a synonym for
891 TIOCM_RNG. Not all of these are necessarily supported by any particular
892 device; check the manual page for the device in question.
893
894 The software carrier mode can be enabled or disabled using the
895 TIOCSSOFTCAR ioctl(). If the software carrier flag for a line is off,
896 the line pays attention to the hardware carrier detect (DCD) signal. The
897 tty device associated with the line cannot be opened until DCD is
898 asserted. If the software carrier flag is on, the line behaves as if DCD
899 is always asserted.
900
901 The software carrier flag is usually turned on for locally connected
902 terminals or other devices, and is off for lines with modems.
903
904 To be able to issue the TIOCGSOFTCAR and TIOCSSOFTCAR ioctl() calls, the
905 tty line should be opened with O_NDELAY so that the open(2) will not wait
906 for the carrier.
907
908 Default Values
909 The initial termios values upon driver open is configurable. This is
910 accomplished by setting the "ttymodes" property in the file
911 /kernel/drv/options.conf. Since this property is assigned during system
912 initialization, any change to the "ttymodes" property will not take
913 effect until the next reboot. The string value assigned to this property
914 should be in the same format as the output of the stty(1) command with
915 the -g option.
916
917 If this property is undefined, the following termios modes are in effect.
918 The initial input control value is BRKINT, ICRNL, IXON, IMAXBEL. The
919 initial output control value is OPOST, ONLCR, TAB3. The initial hardware
920 control value is B9600, CS8, CREAD. The initial line-discipline control
921 value is ISIG, ICANON, IEXTEN, ECHO, ECHOK, ECHOE, ECHOKE, ECHOCTL.
922
923 IOCTLS
924 The ioctl()s supported by devices and STREAMS modules providing the
925 termios(3C) interface are listed below. Some calls may not be supported
926 by all devices or modules. The functionality provided by these calls is
927 also available through the preferred function call interface specified on
928 termios.
929
930 TCGETS The argument is a pointer to a termios structure. The
931 current terminal parameters are fetched and stored into
932 that structure.
933
934 TCSETS The argument is a pointer to a termios structure. The
935 current terminal parameters are set from the values stored
936 in that structure. The change is immediate.
937
938 TCSETSW The argument is a pointer to a termios structure. The
939 current terminal parameters are set from the values stored
940 in that structure. The change occurs after all characters
941 queued for output have been transmitted. This form should
942 be used when changing parameters that affect output.
943
944 TCSETSF The argument is a pointer to a termios structure. The
945 current terminal parameters are set from the values stored
946 in that structure. The change occurs after all characters
947 queued for output have been transmitted; all characters
948 queued for input are discarded and then the change occurs.
949
950 TCGETA The argument is a pointer to a termio structure. The
951 current terminal parameters are fetched, and those
952 parameters that can be stored in a termio structure are
953 stored into that structure.
954
955 TCSETA The argument is a pointer to a termio structure. Those
956 terminal parameters that can be stored in a termio
957 structure are set from the values stored in that structure.
958 The change is immediate.
959
960 TCSETAW The argument is a pointer to a termio structure. Those
961 terminal parameters that can be stored in a termio
962 structure are set from the values stored in that structure.
963 The change occurs after all characters queued for output
964 have been transmitted. This form should be used when
965 changing parameters that affect output.
966
967 TCSETAF The argument is a pointer to a termio structure. Those
968 terminal parameters that can be stored in a termio
969 structure are set from the values stored in that structure.
970 The change occurs after all characters queued for output
971 have been transmitted; all characters queued for input are
972 discarded and then the change occurs.
973
974 TCSBRK The argument is an int value. Wait for the output to
975 drain. If the argument is 0, then send a break (zero
976 valued bits for 0.25 seconds).
977
978 TCXONC Start/stop control. The argument is an int value. If the
979 argument is 0, suspend output; if 1, restart suspended
980 output; if 2, suspend input; if 3, restart suspended input.
981
982 TCFLSH The argument is an int value. If the argument is 0, flush
983 the input queue; if 1, flush the output queue; if 2, flush
984 both the input and output queues.
985
986 TIOCGPGRP The argument is a pointer to a pid_t. Set the value of
987 that pid_t to the process group ID of the foreground
988 process group associated with the terminal. See
989 termios(3C) for a description of TCGETPGRP.
990
991 TIOCSPGRP The argument is a pointer to a pid_t. Associate the
992 process group whose process group ID is specified by the
993 value of that pid_t with the terminal. The new process
994 group value must be in the range of valid process group ID
995 values. Otherwise, the error EPERM is returned.
996
997 TIOCGSID The argument is a pointer to a pid_t. The session ID of
998 the terminal is fetched and stored in the pid_t.
999
1000 TIOCGWINSZ The argument is a pointer to a winsize structure. The
1001 terminal driver's notion of the terminal size is stored
1002 into that structure.
1003
1004 TIOCSWINSZ The argument is a pointer to a winsize structure. The
1005 terminal driver's notion of the terminal size is set from
1006 the values specified in that structure. If the new sizes
1007 are different from the old sizes, a SIGWINCH signal is set
1008 to the process group of the terminal.
1009
1010 TIOCMBIS The argument is a pointer to an int whose value is a mask
1011 containing modem control lines to be turned on. The
1012 control lines whose bits are set in the argument are turned
1013 on; no other control lines are affected.
1014
1015 TIOCMBIC The argument is a pointer to an int whose value is a mask
1016 containing modem control lines to be turned off. The
1017 control lines whose bits are set in the argument are turned
1018 off; no other control lines are affected.
1019
1020 TIOCMGET The argument is a pointer to an int. The current state of
1021 the modem status lines is fetched and stored in the int
1022 pointed to by the argument.
1023
1024 TIOCMSET The argument is a pointer to an int containing a new set of
1025 modem control lines. The modem control lines are turned on
1026 or off, depending on whether the bit for that mode is set
1027 or clear.
1028
1029 TIOCSPPS The argument is a pointer to an int that determines whether
1030 pulse-per-second event handling is to be enabled (non-zero)
1031 or disabled (zero). If a one-pulse-per-second reference
1032 clock is attached to the serial line's data carrier detect
1033 input, the local system clock will be calibrated to it. A
1034 clock with a high error, that is, a deviation of more than
1035 25 microseconds per tick, is ignored.
1036
1037 TIOCGPPS The argument is a pointer to an int, in which the state of
1038 the even handling is returned. The int is set to a non-
1039 zero value if pulse-per-second (PPS) handling has been
1040 enabled. Otherwise, it is set to zero.
1041
1042 TIOCGSOFTCAR The argument is a pointer to an int whose value is 1 or 0,
1043 depending on whether the software carrier detect is turned
1044 on or off.
1045
1046 TIOCSSOFTCAR The argument is a pointer to an int whose value is 1 or 0.
1047 The value of the integer should be 0 to turn off software
1048 carrier, or 1 to turn it on.
1049
1050 TIOCGPPSEV The argument is a pointer to a struct ppsclockev. This
1051 structure contains the following members:
1052
1053 struct timeval tv;
1054 uint32_t serial;
1055
1056 tv is the system clock timestamp when the event (pulse on
1057 the DCD pin) occurred. serial is the ordinal of the event,
1058 which each consecutive event being assigned the next
1059 ordinal. The first event registered gets a serial value of
1060 1. The TIOCGPPSEV returns the last event registered;
1061 multiple calls will persistently return the same event
1062 until a new one is registered. In addition to time
1063 stamping and saving the event, if it is of one-second
1064 period and of consistently high accuracy, the local system
1065 clock will automatically calibrate to it.
1066
1067 FILES
1068 Files in or under /dev
1069
1070 SEE ALSO
1071 stty(1), fork(2), getpgid(2), getsid(2), ioctl(2), setsid(2),
1072 sigaction(2), signal(3C), tcsetpgrp(3C), termios(3C), signal.h(3HEAD),
1073 streamio(7I)
1074
1075 illumos March 17, 2019 illumos