1 .\" Copyright (c) 1991, 1992, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)termios.4 8.4 (Berkeley) 4/19/94
29 .\" $FreeBSD: src/share/man/man4/termios.4,v 1.12.2.9 2001/12/17 11:30:12 ru Exp $
36 .Nd general terminal line discipline
40 This describes a general terminal line discipline that is
41 supported on tty asynchronous communication ports.
42 .Ss Opening a Terminal Device File
43 When a terminal file is opened, it normally causes the process to wait
44 until a connection is established. For most hardware, the presence
45 of a connection is indicated by the assertion of the hardware
48 If the termios structure associated with the terminal file has the
50 flag set in the cflag, or if the
55 call, then the open will succeed even without
56 a connection being present.
57 In practice, applications
58 seldom open these files; they are opened by special programs, such
64 an application's standard input, output, and error files.
65 .Ss Job Control in a Nutshell
66 Every process is associated with a particular process group and session.
67 The grouping is hierarchical: every member of a particular process group is a
68 member of the same session. This structuring is used in managing groups
69 of related processes for purposes of
70 .\" .Gw "job control" ;
73 ability from the keyboard (or from program control) to simultaneously
75 a complex command (a command composed of one or more related
76 processes). The grouping into process groups allows delivering
77 of signals that stop or start the group as a whole, along with
78 arbitrating which process group has access to the single controlling
79 terminal. The grouping at a higher layer into sessions is to restrict
80 the job control related signals and system calls to within processes
81 resulting from a particular instance of a "login". Typically, a session
82 is created when a user logs in, and the login terminal is setup
83 to be the controlling terminal; all processes spawned from that
84 login shell are in the same session, and inherit the controlling
88 operating interactively (that is, reading commands from a terminal)
89 normally groups related processes together by placing them into the
90 same process group. A set of processes in the same process group
91 is collectively referred to as a "job". When the foreground process
92 group of the terminal is the same as the process group of a particular
93 job, that job is said to be in the "foreground". When the process
94 group of the terminal is different from the process group of
95 a job (but is still the controlling terminal), that job is said
96 to be in the "background". Normally the
97 shell reads a command and starts the job that implements that
98 command. If the command is to be started in the foreground (typical), it
99 sets the process group of the terminal to the process group
100 of the started job, waits for the job to complete, and then
101 sets the process group of the terminal back to its own process
102 group (it puts itself into the foreground). If the job is to
103 be started in the background (as denoted by the shell operator "&"),
104 it never changes the process group of the terminal and doesn't
105 wait for the job to complete (that is, it immediately attempts to read the next
106 command). If the job is started in the foreground, the user may
109 which generates the terminal stop signal
111 and has the effect of stopping the entire job.
112 The shell will notice that the job stopped, and will resume running after
113 placing itself in the foreground.
114 The shell also has commands for placing stopped jobs in the background,
115 and for placing stopped or background jobs into the foreground.
116 .Ss Orphaned Process Groups
117 An orphaned process group is a process group that has no process
118 whose parent is in a different process group, yet is in the same
119 session. Conceptually it means a process group that doesn't have
120 a parent that could do anything if it were to be stopped. For example,
121 the initial login shell is typically in an orphaned process group.
122 Orphaned process groups are immune to keyboard generated stop
123 signals and job control signals resulting from reads or writes to the
124 controlling terminal.
125 .Ss The Controlling Terminal
126 A terminal may belong to a process as its controlling terminal. Each
127 process of a session that has a controlling terminal has the same
128 controlling terminal. A terminal may be the controlling terminal for at
129 most one session. The controlling terminal for a session is allocated by
130 the session leader by issuing the
132 ioctl. A controlling terminal
133 is never acquired by merely opening a terminal device file.
134 When a controlling terminal becomes
135 associated with a session, its foreground process group is set to
136 the process group of the session leader.
138 The controlling terminal is inherited by a child process during a
140 function call. A process relinquishes its controlling terminal when it
141 creates a new session with the
143 function; other processes
144 remaining in the old session that had this terminal as their controlling
145 terminal continue to have it.
146 A process does not relinquish its
147 controlling terminal simply by closing all of its file descriptors
148 associated with the controlling terminal if other processes continue to
151 When a controlling process terminates, the controlling terminal is
152 disassociated from the current session, allowing it to be acquired by a
153 new session leader. Subsequent access to the terminal by other processes
154 in the earlier session will be denied, with attempts to access the
155 terminal treated as if modem disconnect had been sensed.
156 .Ss Terminal Access Control
157 If a process is in the foreground process group of its controlling
158 terminal, read operations are allowed.
159 Any attempts by a process
160 in a background process group to read from its controlling terminal
166 following special cases apply: If the reading process is ignoring or
169 signal, or if the process group of the reading
170 process is orphaned, the
177 signal is sent. The default action of the
179 signal is to stop the
180 process to which it is sent.
182 If a process is in the foreground process group of its controlling
183 terminal, write operations are allowed.
184 Attempts by a process in a background process group to write to its
185 controlling terminal will cause the process group to be sent a
187 signal unless one of the following special cases apply: If
192 is set and the process is ignoring or blocking the
194 signal, the process is allowed to write to the terminal and the
196 signal is not sent. If
198 is set, and the process group of
199 the writing process is orphaned, and the writing process is not ignoring
208 and no signal is sent.
210 Certain calls that set terminal parameters are treated in the same
211 fashion as write, except that
213 is ignored; that is, the effect is
214 identical to that of terminal writes when
217 .Ss Input Processing and Reading Data
218 A terminal device associated with a terminal device file may operate in
219 full-duplex mode, so that data may arrive even while output is occurring.
220 Each terminal device file has associated with it an input queue, into
221 which incoming data is stored by the system before being read by a
222 process. The system imposes a limit,
223 .Pf \&{ Dv MAX_INPUT Ns \&} ,
225 bytes that may be stored in the input queue. The behavior of the system
226 when this limit is exceeded depends on the setting of the
230 If this flag is set, the terminal
234 character each time a character is received
235 while the input queue is full. Otherwise, the input queue is flushed
236 upon receiving the character.
238 Two general kinds of input processing are available, determined by
239 whether the terminal device file is in canonical mode or noncanonical
242 input characters are processed according to the
246 fields. Such processing can include echoing, which
247 in general means transmitting input characters immediately back to the
248 terminal when they are received from the terminal. This is useful for
249 terminals that can operate in full-duplex mode.
251 The manner in which data is provided to a process reading from a terminal
252 device file is dependent on whether the terminal device file is in
253 canonical or noncanonical mode.
255 Another dependency is whether the
263 flag is clear, then the read request is
264 blocked until data is available or a signal has been received. If the
266 flag is set, then the read request is completed, without
267 blocking, in one of three ways:
268 .Bl -enum -offset indent
270 If there is enough data available to satisfy the entire request,
271 and the read completes successfully the number of
272 bytes read is returned.
274 If there is not enough data available to satisfy the entire
275 request, and the read completes successfully, having read as
276 much data as possible, the number of bytes read is returned.
278 If there is no data available, the read returns -1, with
284 When data is available depends on whether the input processing mode is
285 canonical or noncanonical.
286 .Ss Canonical Mode Input Processing
287 In canonical mode input processing, terminal input is processed in units
288 of lines. A line is delimited by a newline
290 character, an end-of-file
292 character, or an end-of-line
295 .Sx "Special Characters"
301 This means that a read request will
302 not return until an entire line has been typed, or a signal has been
303 received. Also, no matter how many bytes are requested in the read call,
304 at most one line is returned. It is not, however, necessary to
305 read a whole line at once; any number of bytes, even one, may be
306 requested in a read without losing information.
308 .Pf \&{ Dv MAX_CANON Ns \&}
310 number of bytes in a line.
311 The behavior of the system when this limit is
312 exceeded is the same as when the input queue limit
313 .Pf \&{ Dv MAX_INPUT Ns \&} ,
316 Erase and kill processing occur when either of two special characters,
322 .Sx "Special Characters"
323 section), is received.
324 This processing affects data in the input queue that has not yet been
325 delimited by a newline
330 character. This un-delimited
331 data makes up the current line. The
333 character deletes the last
334 character in the current line, if there is any. The
337 deletes all data in the current line, if there is any. The
341 characters have no effect if there is no data in the current line.
346 characters themselves are not placed in the input
348 .Ss Noncanonical Mode Input Processing
349 In noncanonical mode input processing, input bytes are not assembled into
350 lines, and erase and kill processing does not occur. The values of the
356 array are used to determine how to
357 process the bytes received.
360 represents the minimum number of bytes that should be received when
363 function successfully returns.
365 is a timer of 0.1 second
366 granularity that is used to time out bursty and short term data
370 .Dv \&{ Dv MAX_INPUT Ns \&} ,
372 request is undefined. The four possible values for
377 their interactions are described below.
378 .Ss "Case A: MIN > 0, TIME > 0"
381 serves as an inter-byte timer and is activated after
382 the first byte is received. Since it is an inter-byte timer, it is reset
383 after a byte is received. The interaction between
388 follows: as soon as one byte is received, the inter-byte timer is
391 bytes are received before the inter-byte timer expires
392 (remember that the timer is reset upon receipt of each byte), the read is
393 satisfied. If the timer expires before
395 bytes are received, the
396 characters received to that point are returned to the user. Note that if
398 expires at least one byte is returned because the timer would
399 not have been enabled unless a byte was received. In this case
403 > 0) the read blocks until the
408 activated by the receipt of the first byte, or a signal is received. If
409 data is in the buffer at the time of the
412 if data had been received immediately after the
414 .Ss "Case B: MIN > 0, TIME = 0"
415 In this case, since the value of
417 is zero, the timer plays no role
420 is significant. A pending read is not satisfied until
422 bytes are received (i.e., the pending read blocks until
425 are received), or a signal is received. A program that uses this case to
426 read record-based terminal
428 may block indefinitely in the read
430 .Ss "Case C: MIN = 0, TIME > 0"
435 no longer represents an inter-byte
436 timer. It now serves as a read timer that is activated as soon as the
437 read function is processed. A read is satisfied as soon as a single
438 byte is received or the read timer expires. Note that in this case if
439 the timer expires, no bytes are returned. If the timer does not
440 expire, the only way the read can be satisfied is if a byte is received.
441 In this case the read will not block indefinitely waiting for a byte; if
442 no byte is received within
444 seconds after the read is initiated,
445 the read returns a value of zero, having read no data. If data is
446 in the buffer at the time of the read, the timer is started as if
447 data had been received immediately after the read.
448 .Ss Case D: MIN = 0, TIME = 0
449 The minimum of either the number of bytes requested or the number of
450 bytes currently available is returned without waiting for more
451 bytes to be input. If no characters are available, read returns a
452 value of zero, having read no data.
453 .Ss Writing Data and Output Processing
454 When a process writes one or more bytes to a terminal device file, they
455 are processed according to the
460 implementation may provide a buffering mechanism; as such, when a call to
462 completes, all of the bytes written have been scheduled for
463 transmission to the device, but the transmission will not necessarily
465 .\" See also .Sx "6.4.2" for the effects of
468 .Ss Special Characters
469 Certain characters have special functions on input or output or both.
470 These functions are summarized as follows:
471 .Bl -tag -width indent
473 Special character on input and is recognized if the
477 section) is enabled. Generates a
479 signal which is sent to all processes in the foreground
480 process group for which the terminal is the controlling
486 discarded when processed.
488 Special character on input and is recognized if the
490 flag is enabled. Generates a
493 sent to all processes in the foreground process group
494 for which the terminal is the controlling terminal. If
498 character is discarded when
501 Special character on input and is recognized if the
503 flag is set. Erases the last character in the
505 .Sx "Canonical Mode Input Processing" .
506 It does not erase beyond
507 the start of a line, as delimited by an
517 discarded when processed.
519 Special character on input and is recognized if the
521 flag is set. Deletes the entire line, as
531 character is discarded when processed.
533 Special character on input and is recognized if the
535 flag is set. When received, all the bytes
536 waiting to be read are immediately passed to the
537 process, without waiting for a newline, and the
539 is discarded. Thus, if there are no bytes waiting (that
542 occurred at the beginning of a line), a byte
543 count of zero is returned from the
545 representing an end-of-file indication. If
550 character is discarded when processed.
552 Special character on input and is recognized if the
554 flag is set. It is the line delimiter
557 Special character on input and is recognized if the
559 flag is set. Is an additional line delimiter,
565 flag is enabled, receipt of the
569 signal to be sent to all processes in the
570 foreground process group for which the terminal is the
571 controlling terminal, and the
574 discarded when processed.
576 Special character on both input and output and is
582 control) flag is set. Can be used to temporarily
583 suspend output. It is useful with fast terminals to
584 prevent output from disappearing before it can be read.
589 character is discarded when
592 Special character on both input and output and is
598 control) flag is set. Can be used to resume output that
599 has been suspended by a
605 character is discarded when processed.
607 Special character on input and is recognized if the
609 flag is set; it is the
619 is not set, this character is translated into a
622 has the same effect as a
627 The following special characters are extensions defined by this
628 system and are not a part of
631 .Bl -tag -width indent
635 character. Same function as
638 Special character on input and is recognized if the
640 flag is set. Erases the last word in the current
641 line according to one of two algorithms. If the
643 flag is not set, first any preceding whitespace is
644 erased, and then the maximal sequence of non-whitespace
647 is set, first any preceding
648 whitespace is erased, and then the maximal sequence
649 of alphabetic/underscores or non alphabetic/underscores.
650 As a special case in this second algorithm, the first previous
651 non-whitespace character is skipped in determining
652 whether the preceding word is a sequence of
653 alphabetic/underscores. This sounds confusing but turns
654 out to be quite practical.
656 Special character on input and is recognized if the
658 flag is set. Causes the current input edit line
661 Has similar actions to the
663 character, except that
666 signal is delivered when one of the processes
667 in the foreground process group issues a
670 controlling terminal.
672 Special character on input and is recognized if the
674 flag is set. Receipt of this character causes the next
675 character to be taken literally.
677 Special character on input and is recognized if the
679 flag is set. Receipt of this character toggles the flushing
682 Special character on input and is recognized if the
684 flag is set. Receipt of this character causes a
686 signal to be sent to the foreground process group of the
687 terminal. Also, if the
690 causes the kernel to write a status message to the terminal
691 that displays the current load average, the name of the
692 command in the foreground, its process ID, the symbolic
693 wait channel, the number of user and system seconds used,
694 the percentage of cpu the process is getting, and the resident
695 set size of the process.
702 characters cannot be changed.
703 The values for all the remaining characters can be set and are
704 described later in the document under
705 Special Control Characters.
708 character functions associated with changeable special control characters
709 can be disabled individually by setting their value to
710 .Dv {_POSIX_VDISABLE} ;
712 .Sx "Special Control Characters" .
714 If two or more special characters have the same value, the function
715 performed when that character is received is undefined.
717 If a modem disconnect is detected by the terminal interface for a
718 controlling terminal, and if
725 signal is sent to the controlling
726 process associated with the terminal. Unless other arrangements have
727 been made, this causes the controlling process to terminate.
728 Any subsequent call to the
730 function returns the value zero,
731 indicating end of file. Thus, processes that read a terminal
732 file and test for end-of-file can terminate appropriately after a
736 .\" condition specified in 6.1.1.4 that applies
737 .\" when the implementation supports job control also exists, it is
738 .\" unspecified whether the
746 to the terminal device returns -1, with
750 until the device is closed.
751 .Sh General Terminal Interface
752 .Ss Closing a Terminal Device File
753 The last process to close a terminal device file causes any output
754 to be sent to the device and any input to be discarded. Then, if
756 is set in the control modes, and the communications port supports a
757 disconnect function, the terminal device performs a disconnect.
758 .Ss Parameters That Can Be Set
759 Routines that need to control certain terminal
762 do so by using the termios structure as defined in the header
764 This structure contains minimally four scalar elements of bit flags
765 and one array of special characters. The scalar flag elements are
772 The character array is named
774 and its maximum index is
779 field describe the basic
780 terminal input control, and are composed of
783 .Bl -tag -width IMAXBEL -offset indent -compact
785 /* ignore BREAK condition */
787 /* map BREAK to SIGINTR */
789 /* ignore (discard) parity errors */
791 /* mark parity and framing errors */
793 /* enable checking of parity errors */
795 /* strip 8th bit off chars */
801 /* map CR to NL (ala CRMOD) */
803 /* enable output flow control */
805 /* enable input flow control */
807 /* any char will restart after stop */
809 /* ring bell on input queue full */
812 In the context of asynchronous serial data transmission, a break
813 condition is defined as a sequence of zero-valued bits that continues for
814 more than the time to send one byte. The entire sequence of zero-valued
815 bits is interpreted as a single break condition, even if it continues for
816 a time equivalent to more than one byte. In contexts other than
817 asynchronous serial data transmission the definition of a break condition
818 is implementation defined.
822 is set, a break condition detected on input is ignored, that
823 is, not put on the input queue and therefore not read by any process. If
827 is set, the break condition flushes the
828 input and output queues and if the terminal is the controlling terminal
829 of a foreground process group, the break condition generates a
832 signal to that foreground process group. If neither
836 is set, a break condition is read as a single
847 is set, a byte with a framing or parity error (other than
854 is not set, a byte with a framing or parity
855 error (other than break) is given to the application as the
856 three-character sequence
863 flag preceding each sequence and X is the data of the character received
864 in error. To avoid ambiguity in this case, if
869 is given to the application as
877 is set, a framing or parity error (other than
878 break) is given to the application as a single character
883 is set, input parity checking is enabled. If
886 input parity checking is disabled, allowing output parity generation
887 without input parity errors. Note that whether input parity checking is
888 enabled or disabled is independent of whether parity detection is enabled
890 .Sx "Control Modes" ) .
891 If parity detection is enabled but input
892 parity checking is disabled, the hardware to which the terminal is
893 connected recognizes the parity bit, but the terminal special file
894 does not check whether this bit is set correctly or not.
898 is set, valid input bytes are first stripped to seven bits,
899 otherwise all eight bits are processed.
905 character is translated into a
911 character is ignored (not
925 is set, start/stop output control is enabled. A received
927 character suspends output and a received
933 is also set, then any character may
942 read, but merely perform flow control functions. When
953 is set, start/stop input control is enabled. The system shall
956 characters, which are intended to cause the
957 terminal device to stop transmitting data, as needed to prevent the input
958 queue from overflowing and causing the undefined behavior described in
959 .Sx "Input Processing and Reading Data" ,
960 and shall transmit one or more
962 characters, which are
963 intended to cause the terminal device to resume transmitting data, as
964 soon as the device can continue transmitting data without risk of
965 overflowing the input queue. The precise conditions under which
969 characters are transmitted are implementation defined.
973 is set and the input queue is full, subsequent input shall cause an
976 character to be transmitted to
979 The initial input control value after
981 is implementation defined.
985 field describe the basic terminal output control,
986 and are composed of the following masks:
988 .Bl -tag -width OXTABS -offset indent -compact
990 /* enable following output processing */
992 /* map NL to CR-NL (ala
998 /* expand tabs to spaces */
1005 /* do not transmit CRs on column 0 */
1007 /* on the terminal NL performs the CR function */
1012 is set, the remaining flag masks are interpreted as follows;
1013 otherwise characters are transmitted without change.
1017 is set, newlines are translated to carriage return, linefeeds.
1021 is set, carriage returns are translated to newlines.
1025 is set, tabs are expanded to the appropriate number of
1026 spaces (assuming 8 column tab stops).
1033 are discarded on output.
1037 is set, no CR character is transmitted when at column 0 (first position).
1041 is set, the NL character is assumed to do the carriage-return function;
1042 the column pointer will be set to 0.
1046 field describe the basic
1047 terminal hardware control, and are composed of the
1050 specified are supported by all hardware.
1052 .Bl -tag -width CRTSXIFLOW -offset indent -compact
1054 /* character size mask */
1056 /* 5 bits (pseudo) */
1064 /* send 2 stop bits */
1066 /* enable receiver */
1070 /* odd parity, else even */
1072 /* hang up on last close */
1074 /* ignore modem status lines */
1078 flow control of output */
1084 /* RTS flow control of input */
1086 /* flow control output via Carrier */
1091 bits specify the byte size in bits for both transmission and
1096 and compared with the
1103 This size does not include the parity bit, if any. If
1105 is set, two stop bits are used, otherwise one stop bit. For example, at
1106 110 baud, two stop bits are normally used.
1110 is set, the receiver is enabled. Otherwise, no character is
1112 Not all hardware supports this bit. In fact, this flag
1113 is pretty silly and if it were not part of the
1116 it would be omitted.
1120 is set, parity generation and detection are enabled and a parity
1121 bit is added to each character. If parity is enabled,
1124 odd parity if set, otherwise even parity is used.
1128 is set, the modem control lines for the port are lowered
1129 when the last process with the port open closes the port or the process
1130 terminates. The modem connection is broken.
1134 is set, a connection does not depend on the state of the modem
1137 is clear, the modem status lines are
1140 Under normal circumstances, a call to the
1143 the modem connection to complete. However, if the
1151 immediately without waiting for the connection.
1156 flag is currently unused.
1160 is set then output flow control is controlled by the state
1163 If the object for which the control modes are set is not an asynchronous
1164 serial connection, some of the modes may be ignored; for example, if an
1165 attempt is made to set the baud rate on a network connection to a
1166 terminal on another host, the baud rate may or may not be set on the
1167 connection between that terminal and the machine it is directly connected
1172 field describe the control of
1173 various functions, and are composed of the following
1176 .Bl -tag -width NOKERNINFO -offset indent -compact
1178 /* visual erase for line kill */
1180 /* visually erase chars */
1182 /* enable echoing */
1190 /* visual erase mode for hardcopy */
1192 /* echo control chars as ^(Char) */
1200 /* canonicalize input lines */
1212 /* external processing */
1214 /* stop background jobs from output */
1216 /* output being flushed (state) */
1218 /* no kernel output from
1222 /* XXX retype pending input (state) */
1224 /* don't flush after interrupt */
1229 is set, input characters are echoed back to the terminal. If
1231 is not set, input characters are not echoed.
1239 character causes the terminal
1240 to erase the last character in the current line from the display, if
1241 possible. If there is no character to erase, an implementation may echo
1242 an indication that this was the case or do nothing.
1251 the current line to be discarded and the system echoes the
1264 the current line to be discarded and the system causes
1266 to erase the line from the display.
1272 are set, the system assumes
1273 that the display is a printing device and prints a
1274 backslash and the erased characters when processing
1276 characters, followed by a forward slash.
1280 is set, the system echoes control characters
1281 in a visible fashion using a caret followed by the control character.
1285 is set, the system uses an alternative algorithm
1286 for determining what constitutes a word when processing
1297 character echoes even if
1303 is set, canonical processing is enabled. This enables the
1304 erase and kill edit functions, and the assembly of input characters into
1311 .Sx "Canonical Mode Input Processing" .
1315 is not set, read requests are satisfied directly from the input
1316 queue. A read is not satisfied until at least
1319 received or the timeout value
1321 expired between bytes. The time value
1322 represents tenths of seconds. See
1323 .Sx "Noncanonical Mode Input Processing"
1328 is set, each input character is checked against the special
1334 (job control only). If an input
1335 character matches one of these control characters, the function
1336 associated with that character is performed. If
1339 checking is done. Thus these special input functions are possible only
1346 is set, implementation-defined functions are recognized
1347 from the input data. How
1356 is implementation defined.
1360 implementation-defined functions are not recognized, and the
1361 corresponding input characters are not processed as described for
1370 is set, the normal flush of the input and output queues
1383 is sent to the process group of a process that tries to write to
1384 its controlling terminal if it is not in the foreground process group for
1385 that terminal. This signal, by default, stops the members of the process
1386 group. Otherwise, the output generated by that process is output to the
1387 current output stream. Processes that are blocking or ignoring
1389 signals are excepted and allowed to produce output and the
1396 is set, the kernel does not produce a status message
1401 .Ss Special Control Characters
1402 The special control characters values are defined by the array
1404 This table lists the array index, the corresponding special character,
1405 and the system default value. For an accurate list of
1406 the system defaults, consult the header file
1407 .In sys/ttydefaults.h .
1409 .Bl -column "Index Name" "Special Character" -offset indent -compact
1410 .It Em "Index Name Special Character Default Value"
1411 .It Dv VEOF Ta EOF Ta \&^D
1412 .It Dv VEOL Ta EOL Ta _POSIX_VDISABLE
1413 .It Dv VEOL2 Ta EOL2 Ta _POSIX_VDISABLE
1414 .It Dv VERASE Ta ERASE Ta \&^? Ql \&\e177
1415 .It Dv VWERASE Ta WERASE Ta \&^W
1416 .It Dv VKILL Ta KILL Ta \&^U
1417 .It Dv VREPRINT Ta REPRINT Ta \&^R
1418 .It Dv VINTR Ta INTR Ta \&^C
1419 .It Dv VQUIT Ta QUIT Ta \&^\e\e Ql \&\e34
1420 .It Dv VSUSP Ta SUSP Ta \&^Z
1421 .It Dv VDSUSP Ta DSUSP Ta \&^Y
1422 .It Dv VSTART Ta START Ta \&^Q
1423 .It Dv VSTOP Ta STOP Ta \&^S
1424 .It Dv VLNEXT Ta LNEXT Ta \&^V
1425 .It Dv VDISCARD Ta DISCARD Ta \&^O
1426 .It Dv VMIN Ta --- Ta \&1
1427 .It Dv VTIME Ta --- Ta \&0
1428 .It Dv VSTATUS Ta STATUS Ta \&^T
1432 value of one of the changeable special control characters (see
1433 .Sx "Special Characters" )
1435 .Dv {_POSIX_VDISABLE} ,
1436 that function is disabled; that is, no input
1437 data is recognized as the disabled special character.
1441 not set, the value of
1442 .Dv {_POSIX_VDISABLE}
1443 has no special meaning for the
1451 The initial values of the flags and control characters
1455 the values in the header
1456 .In sys/ttydefaults.h .