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
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15 .\" California, Berkeley and its contributors.
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20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)termios.4 8.4 (Berkeley) 4/19/94
40 .Nd general terminal line discipline
44 This describes a general terminal line discipline that is
45 supported on tty asynchronous communication ports.
46 .Ss Opening a Terminal Device File
47 When a terminal file is opened, it normally causes the process to wait
48 until a connection is established.
49 For most hardware, the presence
50 of a connection is indicated by the assertion of the hardware
53 If the termios structure associated with the terminal file has the
55 flag set in the cflag, or if the
60 call, then the open will succeed even without
61 a connection being present.
62 In practice, applications
63 seldom open these files; they are opened by special programs, such
69 an application's standard input, output, and error files.
70 .Ss Job Control in a Nutshell
71 Every process is associated with a particular process group and session.
72 The grouping is hierarchical: every member of a particular process group is a
73 member of the same session.
74 This structuring is used in managing groups
75 of related processes for purposes of
76 .\" .Gw "job control" ;
79 ability from the keyboard (or from program control) to simultaneously
81 a complex command (a command composed of one or more related
83 The grouping into process groups allows delivering
84 of signals that stop or start the group as a whole, along with
85 arbitrating which process group has access to the single controlling
87 The grouping at a higher layer into sessions is to restrict
88 the job control related signals and system calls to within processes
89 resulting from a particular instance of a
92 is created when a user logs in, and the login terminal is setup
93 to be the controlling terminal; all processes spawned from that
94 login shell are in the same session, and inherit the controlling
98 operating interactively (that is, reading commands from a terminal)
99 normally groups related processes together by placing them into the
101 A set of processes in the same process group
102 is collectively referred to as a
104 When the foreground process
105 group of the terminal is the same as the process group of a particular
106 job, that job is said to be in the
108 When the process group of the terminal is different from the process group of
109 a job (but is still the controlling terminal), that job is said
113 shell reads a command and starts the job that implements that
115 If the command is to be started in the foreground (typical), it
116 sets the process group of the terminal to the process group
117 of the started job, waits for the job to complete, and then
118 sets the process group of the terminal back to its own process
119 group (it puts itself into the foreground).
121 be started in the background (as denoted by the shell operator "&"),
122 it never changes the process group of the terminal and does not
123 wait for the job to complete (that is, it immediately attempts to read the next
125 If the job is started in the foreground, the user may
128 which generates the terminal stop signal
130 and has the effect of stopping the entire job.
131 The shell will notice that the job stopped, and will resume running after
132 placing itself in the foreground.
133 The shell also has commands for placing stopped jobs in the background,
134 and for placing stopped or background jobs into the foreground.
135 .Ss Orphaned Process Groups
136 An orphaned process group is a process group that has no process
137 whose parent is in a different process group, yet is in the same
139 Conceptually it means a process group that does not have
140 a parent that could do anything if it were to be stopped.
142 the initial login shell is typically in an orphaned process group.
143 Orphaned process groups are immune to keyboard generated stop
144 signals and job control signals resulting from reads or writes to the
145 controlling terminal.
146 .Ss The Controlling Terminal
147 A terminal may belong to a process as its controlling terminal.
149 process of a session that has a controlling terminal has the same
150 controlling terminal.
151 A terminal may be the controlling terminal for at
153 The controlling terminal for a session is allocated by
154 the session leader by issuing the
157 A controlling terminal
158 is never acquired by merely opening a terminal device file.
159 When a controlling terminal becomes
160 associated with a session, its foreground process group is set to
161 the process group of the session leader.
163 The controlling terminal is inherited by a child process during a
166 A process relinquishes its controlling terminal when it
167 creates a new session with the
169 function; other processes
170 remaining in the old session that had this terminal as their controlling
171 terminal continue to have it.
172 A process does not relinquish its
173 controlling terminal simply by closing all of its file descriptors
174 associated with the controlling terminal if other processes continue to
177 When a controlling process terminates, the controlling terminal is
178 disassociated from the current session, allowing it to be acquired by a
180 Subsequent access to the terminal by other processes
181 in the earlier session will be denied, with attempts to access the
182 terminal treated as if modem disconnect had been sensed.
183 .Ss Terminal Access Control
184 If a process is in the foreground process group of its controlling
185 terminal, read operations are allowed.
186 Any attempts by a process
187 in a background process group to read from its controlling terminal
193 following special cases apply: if the reading process is ignoring or
196 signal, or if the process group of the reading
197 process is orphaned, the
205 The default action of the
207 signal is to stop the
208 process to which it is sent.
210 If a process is in the foreground process group of its controlling
211 terminal, write operations are allowed.
212 Attempts by a process in a background process group to write to its
213 controlling terminal will cause the process group to be sent a
215 signal unless one of the following special cases apply: if
220 is set and the process is ignoring or blocking the
222 signal, the process is allowed to write to the terminal and the
227 is set, and the process group of
228 the writing process is orphaned, and the writing process is not ignoring
236 and no signal is sent.
238 Certain calls that set terminal parameters are treated in the same
239 fashion as write, except that
241 is ignored; that is, the effect is
242 identical to that of terminal writes when
245 .Ss Input Processing and Reading Data
246 A terminal device associated with a terminal device file may operate in
247 full-duplex mode, so that data may arrive even while output is occurring.
248 Each terminal device file has associated with it an input queue, into
249 which incoming data is stored by the system before being read by a
251 The system imposes a limit,
252 .Pf \&{ Dv MAX_INPUT Ns \&} ,
254 bytes that may be stored in the input queue.
255 The behavior of the system
256 when this limit is exceeded depends on the setting of the
260 If this flag is set, the terminal
264 character each time a character is received
265 while the input queue is full.
266 Otherwise, the input queue is flushed upon receiving the character.
268 Two general kinds of input processing are available, determined by
269 whether the terminal device file is in canonical mode or noncanonical
272 input characters are processed according to the
277 Such processing can include echoing, which
278 in general means transmitting input characters immediately back to the
279 terminal when they are received from the terminal.
280 This is useful for terminals that can operate in full-duplex mode.
282 The manner in which data is provided to a process reading from a terminal
283 device file is dependent on whether the terminal device file is in
284 canonical or noncanonical mode.
286 Another dependency is whether the
294 flag is clear, then the read request is
295 blocked until data is available or a signal has been received.
298 flag is set, then the read request is completed, without
299 blocking, in one of three ways:
300 .Bl -enum -offset indent
302 If there is enough data available to satisfy the entire request,
303 and the read completes successfully the number of
304 bytes read is returned.
306 If there is not enough data available to satisfy the entire
307 request, and the read completes successfully, having read as
308 much data as possible, the number of bytes read is returned.
310 If there is no data available, the read returns -1, with
315 When data is available depends on whether the input processing mode is
316 canonical or noncanonical.
317 .Ss Canonical Mode Input Processing
318 In canonical mode input processing, terminal input is processed in units
320 A line is delimited by a newline
322 character, an end-of-file
324 character, or an end-of-line
328 .Sx "Special Characters"
334 This means that a read request will
335 not return until an entire line has been typed, or a signal has been
337 Also, no matter how many bytes are requested in the read call,
338 at most one line is returned.
339 It is not, however, necessary to
340 read a whole line at once; any number of bytes, even one, may be
341 requested in a read without losing information.
343 .Pf \&{ Dv MAX_CANON Ns \&}
345 number of bytes in a line.
346 The behavior of the system when this limit is
347 exceeded is the same as when the input queue limit
348 .Pf \&{ Dv MAX_INPUT Ns \&} ,
351 Erase and kill processing occur when either of two special characters,
357 .Sx "Special Characters"
358 section), is received.
359 This processing affects data in the input queue that has not yet been
360 delimited by a newline
367 data makes up the current line.
370 character deletes the last
371 character in the current line, if there is any.
375 deletes all data in the current line, if there is any.
380 characters have no effect if there is no data in the current line.
385 characters themselves are not placed in the input
387 .Ss Noncanonical Mode Input Processing
388 In noncanonical mode input processing, input bytes are not assembled into
389 lines, and erase and kill processing does not occur.
396 array are used to determine how to
397 process the bytes received.
400 represents the minimum number of bytes that should be received when
403 function successfully returns.
405 is a timer of 0.1 second
406 granularity that is used to time out bursty and short term data
411 .Dv \&{ Dv MAX_INPUT Ns \&} ,
413 request is undefined.
414 The four possible values for
419 their interactions are described below.
420 .Ss "Case A: MIN > 0, TIME > 0"
423 serves as an inter-byte timer and is activated after
424 the first byte is received.
425 Since it is an inter-byte timer, it is reset
426 after a byte is received.
427 The interaction between
432 follows: as soon as one byte is received, the inter-byte timer is
436 bytes are received before the inter-byte timer expires
437 (remember that the timer is reset upon receipt of each byte), the read is
439 If the timer expires before
441 bytes are received, the
442 characters received to that point are returned to the user.
445 expires at least one byte is returned because the timer would
446 not have been enabled unless a byte was received.
451 > 0) the read blocks until the
456 activated by the receipt of the first byte, or a signal is received.
457 If data is in the buffer at the time of the
460 if data had been received immediately after the
462 .Ss "Case B: MIN > 0, TIME = 0"
463 In this case, since the value of
465 is zero, the timer plays no role
469 A pending read is not satisfied until
471 bytes are received (i.e., the pending read blocks until
474 are received), or a signal is received.
475 A program that uses this case to read record-based terminal
477 may block indefinitely in the read
479 .Ss "Case C: MIN = 0, TIME > 0"
484 no longer represents an inter-byte
486 It now serves as a read timer that is activated as soon as the
487 read function is processed.
488 A read is satisfied as soon as a single
489 byte is received or the read timer expires.
490 Note that in this case if the timer expires, no bytes are returned.
491 If the timer does not
492 expire, the only way the read can be satisfied is if a byte is received.
493 In this case the read will not block indefinitely waiting for a byte; if
494 no byte is received within
496 seconds after the read is initiated,
497 the read returns a value of zero, having read no data.
499 in the buffer at the time of the read, the timer is started as if
500 data had been received immediately after the read.
501 .Ss Case D: MIN = 0, TIME = 0
502 The minimum of either the number of bytes requested or the number of
503 bytes currently available is returned without waiting for more
505 If no characters are available, read returns a
506 value of zero, having read no data.
507 .Ss Writing Data and Output Processing
508 When a process writes one or more bytes to a terminal device file, they
509 are processed according to the
515 implementation may provide a buffering mechanism; as such, when a call to
517 completes, all of the bytes written have been scheduled for
518 transmission to the device, but the transmission will not necessarily
520 .\" See also .Sx "6.4.2" for the effects of
523 .Ss Special Characters
524 Certain characters have special functions on input or output or both.
525 These functions are summarized as follows:
526 .Bl -tag -width indent
528 Special character on input and is recognized if the
535 signal which is sent to all processes in the foreground
536 process group for which the terminal is the controlling
543 discarded when processed.
545 Special character on input and is recognized if the
551 sent to all processes in the foreground process group
552 for which the terminal is the controlling terminal.
557 character is discarded when
560 Special character on input and is recognized if the
563 Erases the last character in the
565 .Sx "Canonical Mode Input Processing" .
566 It does not erase beyond
567 the start of a line, as delimited by an
578 discarded when processed.
580 Special character on input and is recognized if the
583 Deletes the entire line, as
594 character is discarded when processed.
596 Special character on input and is recognized if the
599 When received, all the bytes
600 waiting to be read are immediately passed to the
601 process, without waiting for a newline, and the
604 Thus, if there are no bytes waiting (that is, the
606 occurred at the beginning of a line), a byte
607 count of zero is returned from the
609 representing an end-of-file indication.
615 character is discarded when processed.
617 Special character on input and is recognized if the
620 It is the line delimiter
623 Special character on input and is recognized if the
626 Is an additional line delimiter, like
631 flag is enabled, receipt of the
635 signal to be sent to all processes in the
636 foreground process group for which the terminal is the
637 controlling terminal, and the
640 discarded when processed.
642 Special character on both input and output and is
648 control) flag is set.
649 Can be used to temporarily suspend output.
650 It is useful with fast terminals to
651 prevent output from disappearing before it can be read.
656 character is discarded when
659 Special character on both input and output and is
665 control) flag is set.
666 Can be used to resume output that has been suspended by a
673 character is discarded when processed.
675 Special character on input and is recognized if the
677 flag is set; it is the
688 is not set, this character is translated into a
691 has the same effect as a
696 The following special characters are extensions defined by this
697 system and are not a part of
700 .Bl -tag -width indent
708 Special character on input and is recognized if the
711 Erases the last word in the current line according to one of two algorithms.
714 flag is not set, first any preceding whitespace is
715 erased, and then the maximal sequence of non-whitespace
719 is set, first any preceding
720 whitespace is erased, and then the maximal sequence
721 of alphabetic/underscores or non alphabetic/underscores.
722 As a special case in this second algorithm, the first previous
723 non-whitespace character is skipped in determining
724 whether the preceding word is a sequence of
725 alphabetic/underscores.
726 This sounds confusing but turns out to be quite practical.
728 Special character on input and is recognized if the
731 Causes the current input edit line to be retyped.
733 Has similar actions to the
735 character, except that
738 signal is delivered when one of the processes
739 in the foreground process group issues a
742 controlling terminal.
744 Special character on input and is recognized if the
747 Receipt of this character causes the next character to be taken literally.
749 Special character on input and is recognized if the
752 Receipt of this character toggles the flushing of terminal output.
754 Special character on input and is recognized if the
757 Receipt of this character causes a
759 signal to be sent to the foreground process group of the
764 causes the kernel to write a status message to the terminal
765 that displays the current load average, the name of the
766 command in the foreground, its process ID, the symbolic
767 wait channel, the number of user and system seconds used,
768 the percentage of cpu the process is getting, and the resident
769 set size of the process.
776 characters cannot be changed.
777 The values for all the remaining characters can be set and are
778 described later in the document under
779 Special Control Characters.
782 character functions associated with changeable special control characters
783 can be disabled individually by setting their value to
784 .Dv {_POSIX_VDISABLE} ;
786 .Sx "Special Control Characters" .
788 If two or more special characters have the same value, the function
789 performed when that character is received is undefined.
791 If a modem disconnect is detected by the terminal interface for a
792 controlling terminal, and if
799 signal is sent to the controlling
800 process associated with the terminal.
801 Unless other arrangements have
802 been made, this causes the controlling process to terminate.
803 Any subsequent call to the
805 function returns the value zero,
806 indicating end of file.
807 Thus, processes that read a terminal
808 file and test for end-of-file can terminate appropriately after a
812 .\" condition specified in 6.1.1.4 that applies
813 .\" when the implementation supports job control also exists, it is
814 .\" unspecified whether the
822 to the terminal device returns -1, with
826 until the device is closed.
827 .Sh General Terminal Interface
828 .Ss Closing a Terminal Device File
829 The last process to close a terminal device file causes any output
830 to be sent to the device and any input to be discarded.
833 is set in the control modes, and the communications port supports a
834 disconnect function, the terminal device performs a disconnect.
835 .Ss Parameters That Can Be Set
836 Routines that need to control certain terminal
839 do so by using the termios structure as defined in the header
841 This structure contains minimally four scalar elements of bit flags
842 and one array of special characters.
843 The scalar flag elements are named:
849 The character array is named
851 and its maximum index is
856 field describe the basic
857 terminal input control, and are composed of
860 .Bl -tag -width IMAXBEL -offset indent -compact
862 /* ignore BREAK condition */
864 /* map BREAK to SIGINTR */
866 /* ignore (discard) parity errors */
868 /* mark parity and framing errors */
870 /* enable checking of parity errors */
872 /* strip 8th bit off chars */
878 /* map CR to NL (ala CRMOD) */
880 /* enable output flow control */
882 /* enable input flow control */
884 /* any char will restart after stop */
886 /* ring bell on input queue full */
889 In the context of asynchronous serial data transmission, a break
890 condition is defined as a sequence of zero-valued bits that continues for
891 more than the time to send one byte.
892 The entire sequence of zero-valued
893 bits is interpreted as a single break condition, even if it continues for
894 a time equivalent to more than one byte.
895 In contexts other than
896 asynchronous serial data transmission the definition of a break condition
897 is implementation defined.
901 is set, a break condition detected on input is ignored, that
902 is, not put on the input queue and therefore not read by any process.
907 is set, the break condition flushes the
908 input and output queues and if the terminal is the controlling terminal
909 of a foreground process group, the break condition generates a
912 signal to that foreground process group.
917 is set, a break condition is read as a single
928 is set, a byte with a framing or parity error (other than
935 is not set, a byte with a framing or parity
936 error (other than break) is given to the application as the
937 three-character sequence
944 flag preceding each sequence and X is the data of the character received
946 To avoid ambiguity in this case, if
951 is given to the application as
959 is set, a framing or parity error (other than
960 break) is given to the application as a single character
965 is set, input parity checking is enabled.
969 input parity checking is disabled, allowing output parity generation
970 without input parity errors.
971 Note that whether input parity checking is
972 enabled or disabled is independent of whether parity detection is enabled
974 .Sx "Control Modes" ) .
975 If parity detection is enabled but input
976 parity checking is disabled, the hardware to which the terminal is
977 connected recognizes the parity bit, but the terminal special file
978 does not check whether this bit is set correctly or not.
982 is set, valid input bytes are first stripped to seven bits,
983 otherwise all eight bits are processed.
989 character is translated into a
996 character is ignored (not
1011 is set, start/stop output control is enabled.
1014 character suspends output and a received
1020 is also set, then any character may
1029 read, but merely perform flow control functions.
1037 characters are read.
1041 is set, start/stop input control is enabled.
1042 The system shall transmit one or more
1044 characters, which are intended to cause the
1045 terminal device to stop transmitting data, as needed to prevent the input
1046 queue from overflowing and causing the undefined behavior described in
1047 .Sx "Input Processing and Reading Data" ,
1048 and shall transmit one or more
1050 characters, which are
1051 intended to cause the terminal device to resume transmitting data, as
1052 soon as the device can continue transmitting data without risk of
1053 overflowing the input queue.
1054 The precise conditions under which
1058 characters are transmitted are implementation defined.
1062 is set and the input queue is full, subsequent input shall cause an
1065 character to be transmitted to
1068 The initial input control value after
1070 is implementation defined.
1074 field describe the basic terminal output control,
1075 and are composed of the following masks:
1077 .Bl -tag -width ONOEOT -offset indent -compact
1079 /* enable following output processing */
1081 /* map NL to CR-NL (ala
1087 /* tab delay mask */
1089 /* no tab delay and expansion */
1091 /* expand tabs to spaces */
1098 /* do not transmit CRs on column 0 */
1100 /* on the terminal NL performs the CR function */
1105 is set, the remaining flag masks are interpreted as follows;
1106 otherwise characters are transmitted without change.
1110 is set, newlines are translated to carriage return, linefeeds.
1114 is set, carriage returns are translated to newlines.
1118 bits specify the tab delay.
1123 and compared with the
1130 is set, tabs are expanded to the appropriate number of
1131 spaces (assuming 8 column tab stops).
1138 are discarded on output.
1142 is set, no CR character is transmitted when at column 0 (first position).
1146 is set, the NL character is assumed to do the carriage-return function;
1147 the column pointer will be set to 0.
1151 field describe the basic
1152 terminal hardware control, and are composed of the
1155 specified are supported by all hardware.
1157 .Bl -tag -width CRTSXIFLOW -offset indent -compact
1159 /* character size mask */
1161 /* 5 bits (pseudo) */
1169 /* send 2 stop bits */
1171 /* enable receiver */
1175 /* odd parity, else even */
1177 /* hang up on last close */
1179 /* ignore modem status lines */
1183 flow control of output */
1189 /* RTS flow control of input */
1191 /* flow control output via Carrier */
1196 bits specify the byte size in bits for both transmission and
1202 and compared with the
1209 This size does not include the parity bit, if any.
1212 is set, two stop bits are used, otherwise one stop bit.
1213 For example, at 110 baud, two stop bits are normally used.
1217 is set, the receiver is enabled.
1218 Otherwise, no character is received.
1219 Not all hardware supports this bit.
1220 In fact, this flag is pretty silly and if it were not part of the
1223 it would be omitted.
1227 is set, parity generation and detection are enabled and a parity
1228 bit is added to each character.
1229 If parity is enabled,
1232 odd parity if set, otherwise even parity is used.
1236 is set, the modem control lines for the port are lowered
1237 when the last process with the port open closes the port or the process
1239 The modem connection is broken.
1243 is set, a connection does not depend on the state of the modem
1247 is clear, the modem status lines are
1250 Under normal circumstances, a call to the
1253 the modem connection to complete.
1262 immediately without waiting for the connection.
1267 flag is currently unused.
1271 is set then output flow control is controlled by the state
1274 If the object for which the control modes are set is not an asynchronous
1275 serial connection, some of the modes may be ignored; for example, if an
1276 attempt is made to set the baud rate on a network connection to a
1277 terminal on another host, the baud rate may or may not be set on the
1278 connection between that terminal and the machine it is directly connected
1283 field describe the control of
1284 various functions, and are composed of the following
1287 .Bl -tag -width NOKERNINFO -offset indent -compact
1289 /* visual erase for line kill */
1291 /* visually erase chars */
1293 /* enable echoing */
1301 /* visual erase mode for hardcopy */
1303 /* echo control chars as ^(Char) */
1311 /* canonicalize input lines */
1323 /* external processing */
1325 /* stop background jobs from output */
1327 /* output being flushed (state) */
1329 /* no kernel output from
1333 /* XXX retype pending input (state) */
1335 /* don't flush after interrupt */
1340 is set, input characters are echoed back to the terminal.
1343 is not set, input characters are not echoed.
1351 character causes the terminal
1352 to erase the last character in the current line from the display, if
1354 If there is no character to erase, an implementation may echo
1355 an indication that this was the case or do nothing.
1364 the current line to be discarded and the system echoes the
1377 the current line to be discarded and the system causes
1379 to erase the line from the display.
1385 are set, the system assumes
1386 that the display is a printing device and prints a
1387 backslash and the erased characters when processing
1389 characters, followed by a forward slash.
1393 is set, the system echoes control characters
1394 in a visible fashion using a caret followed by the control character.
1398 is set, the system uses an alternative algorithm
1399 for determining what constitutes a word when processing
1410 character echoes even if
1416 is set, canonical processing is enabled.
1418 erase and kill edit functions, and the assembly of input characters into
1425 .Sx "Canonical Mode Input Processing" .
1429 is not set, read requests are satisfied directly from the input
1431 A read is not satisfied until at least
1434 received or the timeout value
1436 expired between bytes.
1438 represents tenths of seconds.
1440 .Sx "Noncanonical Mode Input Processing"
1445 is set, each input character is checked against the special
1453 character matches one of these control characters, the function
1454 associated with that character is performed.
1459 Thus these special input functions are possible only
1466 is set, implementation-defined functions are recognized
1467 from the input data.
1477 is implementation defined.
1481 implementation-defined functions are not recognized, and the
1482 corresponding input characters are not processed as described for
1491 is set, the normal flush of the input and output queues
1504 is sent to the process group of a process that tries to write to
1505 its controlling terminal if it is not in the foreground process group for
1507 This signal, by default, stops the members of the process group.
1508 Otherwise, the output generated by that process is output to the
1509 current output stream.
1510 Processes that are blocking or ignoring
1512 signals are excepted and allowed to produce output and the
1519 is set, the kernel does not produce a status message
1524 .Ss Special Control Characters
1525 The special control characters values are defined by the array
1527 This table lists the array index, the corresponding special character,
1528 and the system default value.
1529 For an accurate list of
1530 the system defaults, consult the header file
1531 .In sys/ttydefaults.h .
1533 .Bl -column "Index Name" "Special Character" -offset indent -compact
1534 .It Em "Index Name Special Character Default Value"
1535 .It Dv VEOF Ta EOF Ta \&^D
1536 .It Dv VEOL Ta EOL Ta _POSIX_VDISABLE
1537 .It Dv VEOL2 Ta EOL2 Ta _POSIX_VDISABLE
1538 .It Dv VERASE Ta ERASE Ta \&^? Ql \&\e177
1539 .It Dv VWERASE Ta WERASE Ta \&^W
1540 .It Dv VKILL Ta KILL Ta \&^U
1541 .It Dv VREPRINT Ta REPRINT Ta \&^R
1542 .It Dv VINTR Ta INTR Ta \&^C
1543 .It Dv VQUIT Ta QUIT Ta \&^\e\e Ql \&\e34
1544 .It Dv VSUSP Ta SUSP Ta \&^Z
1545 .It Dv VDSUSP Ta DSUSP Ta \&^Y
1546 .It Dv VSTART Ta START Ta \&^Q
1547 .It Dv VSTOP Ta STOP Ta \&^S
1548 .It Dv VLNEXT Ta LNEXT Ta \&^V
1549 .It Dv VDISCARD Ta DISCARD Ta \&^O
1550 .It Dv VMIN Ta --- Ta \&1
1551 .It Dv VTIME Ta --- Ta \&0
1552 .It Dv VSTATUS Ta STATUS Ta \&^T
1556 value of one of the changeable special control characters (see
1557 .Sx "Special Characters" )
1559 .Dv {_POSIX_VDISABLE} ,
1560 that function is disabled; that is, no input
1561 data is recognized as the disabled special character.
1565 not set, the value of
1566 .Dv {_POSIX_VDISABLE}
1567 has no special meaning for the
1575 The initial values of the flags and control characters
1579 the values in the header
1580 .In sys/ttydefaults.h .