1termios(3)                 Library Functions Manual                 termios(3)
2
3
4

NAME

6       termios,  tcgetattr,  tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow,
7       cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed,  cfsetospeed,  cfset‐
8       speed - get and set terminal attributes, line control, get and set baud
9       rate
10

LIBRARY

12       Standard C library (libc, -lc)
13

SYNOPSIS

15       #include <termios.h>
16       #include <unistd.h>
17
18       int tcgetattr(int fd, struct termios *termios_p);
19       int tcsetattr(int fd, int optional_actions,
20                     const struct termios *termios_p);
21
22       int tcsendbreak(int fd, int duration);
23       int tcdrain(int fd);
24       int tcflush(int fd, int queue_selector);
25       int tcflow(int fd, int action);
26
27       void cfmakeraw(struct termios *termios_p);
28
29       speed_t cfgetispeed(const struct termios *termios_p);
30       speed_t cfgetospeed(const struct termios *termios_p);
31
32       int cfsetispeed(struct termios *termios_p, speed_t speed);
33       int cfsetospeed(struct termios *termios_p, speed_t speed);
34       int cfsetspeed(struct termios *termios_p, speed_t speed);
35
36   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
37
38       cfsetspeed(), cfmakeraw():
39           Since glibc 2.19:
40               _DEFAULT_SOURCE
41           glibc 2.19 and earlier:
42               _BSD_SOURCE
43

DESCRIPTION

45       The termios functions describe a general  terminal  interface  that  is
46       provided to control asynchronous communications ports.
47
48   The termios structure
49       Many  of the functions described here have a termios_p argument that is
50       a pointer to a termios structure.  This structure contains at least the
51       following members:
52
53           tcflag_t c_iflag;      /* input modes */
54           tcflag_t c_oflag;      /* output modes */
55           tcflag_t c_cflag;      /* control modes */
56           tcflag_t c_lflag;      /* local modes */
57           cc_t     c_cc[NCCS];   /* special characters */
58
59       The  values  that  may be assigned to these fields are described below.
60       In the case of the first four bit-mask fields, the definitions of  some
61       of  the associated flags that may be set are exposed only if a specific
62       feature test macro (see feature_test_macros(7)) is defined, as noted in
63       brackets ("[]").
64
65       In  the  descriptions below, "not in POSIX" means that the value is not
66       specified in POSIX.1-2001, and "XSI" means that the value is  specified
67       in POSIX.1-2001 as part of the XSI extension.
68
69       c_iflag flag constants:
70
71       IGNBRK Ignore BREAK condition on input.
72
73       BRKINT If  IGNBRK  is  set,  a  BREAK is ignored.  If it is not set but
74              BRKINT is set, then a BREAK causes the input and  output  queues
75              to  be  flushed, and if the terminal is the controlling terminal
76              of a foreground process group, it will cause a SIGINT to be sent
77              to  this  foreground  process  group.   When  neither IGNBRK nor
78              BRKINT are set, a BREAK reads as a null byte ('\0'), except when
79              PARMRK  is  set,  in which case it reads as the sequence \377 \0
80              \0.
81
82       IGNPAR Ignore framing errors and parity errors.
83
84       PARMRK If this bit is set, input bytes with parity  or  framing  errors
85              are  marked  when passed to the program.  This bit is meaningful
86              only when INPCK is set and IGNPAR is not set.  The way erroneous
87              bytes  are  marked  is  with  two  preceding bytes, \377 and \0.
88              Thus, the program actually reads three bytes for  one  erroneous
89              byte  received from the terminal.  If a valid byte has the value
90              \377, and ISTRIP (see below) is not set, the program might  con‐
91              fuse it with the prefix that marks a parity error.  Therefore, a
92              valid byte \377 is passed to the  program  as  two  bytes,  \377
93              \377, in this case.
94
95              If  neither  IGNPAR  nor  PARMRK is set, read a character with a
96              parity error or framing error as \0.
97
98       INPCK  Enable input parity checking.
99
100       ISTRIP Strip off eighth bit.
101
102       INLCR  Translate NL to CR on input.
103
104       IGNCR  Ignore carriage return on input.
105
106       ICRNL  Translate carriage return to newline on input (unless  IGNCR  is
107              set).
108
109       IUCLC  (not in POSIX) Map uppercase characters to lowercase on input.
110
111       IXON   Enable XON/XOFF flow control on output.
112
113       IXANY  (XSI)  Typing  any  character will restart stopped output.  (The
114              default is to allow just the START character to restart output.)
115
116       IXOFF  Enable XON/XOFF flow control on input.
117
118       IMAXBEL
119              (not in POSIX) Ring bell when input queue is full.   Linux  does
120              not implement this bit, and acts as if it is always set.
121
122       IUTF8 (since Linux 2.6.4)
123              (not  in POSIX) Input is UTF8; this allows character-erase to be
124              correctly performed in cooked mode.
125
126       c_oflag flag constants:
127
128       OPOST  Enable implementation-defined output processing.
129
130       OLCUC  (not in POSIX) Map lowercase characters to uppercase on output.
131
132       ONLCR  (XSI) Map NL to CR-NL on output.
133
134       OCRNL  Map CR to NL on output.
135
136       ONOCR  Don't output CR at column 0.
137
138       ONLRET The NL character is assumed to do the carriage-return  function;
139              the  kernel's  idea of the current column is set to 0 after both
140              NL and CR.
141
142       OFILL  Send fill characters for a delay, rather than using a timed  de‐
143              lay.
144
145       OFDEL  Fill character is ASCII DEL (0177).  If unset, fill character is
146              ASCII NUL ('\0').  (Not implemented on Linux.)
147
148       NLDLY  Newline  delay  mask.   Values  are  NL0  and  NL1.    [requires
149              _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]
150
151       CRDLY  Carriage  return  delay mask.  Values are CR0, CR1, CR2, or CR3.
152              [requires _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]
153
154       TABDLY Horizontal tab delay mask.  Values are TAB0,  TAB1,  TAB2,  TAB3
155              (or XTABS, but see the BUGS section).  A value of TAB3, that is,
156              XTABS, expands tabs to spaces (with tab stops every  eight  col‐
157              umns).  [requires _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]
158
159       BSDLY  Backspace  delay  mask.  Values are BS0 or BS1.  (Has never been
160              implemented.)   [requires   _BSD_SOURCE   or   _SVID_SOURCE   or
161              _XOPEN_SOURCE]
162
163       VTDLY  Vertical tab delay mask.  Values are VT0 or VT1.
164
165       FFDLY  Form  feed  delay  mask.   Values  are  FF0  or  FF1.  [requires
166              _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]
167
168       c_cflag flag constants:
169
170       CBAUD  (not  in  POSIX)  Baud  speed  mask   (4+1   bits).    [requires
171              _BSD_SOURCE or _SVID_SOURCE]
172
173       CBAUDEX
174              (not in POSIX) Extra baud speed mask (1 bit), included in CBAUD.
175              [requires _BSD_SOURCE or _SVID_SOURCE]
176
177              (POSIX says that the baud speed is stored in the termios  struc‐
178              ture   without   specifying   where   precisely,   and  provides
179              cfgetispeed() and cfsetispeed() for getting at it.  Some systems
180              use  bits  selected by CBAUD in c_cflag, other systems use sepa‐
181              rate fields, for example, sg_ispeed and sg_ospeed.)
182
183       CSIZE  Character size mask.  Values are CS5, CS6, CS7, or CS8.
184
185       CSTOPB Set two stop bits, rather than one.
186
187       CREAD  Enable receiver.
188
189       PARENB Enable parity generation on output and parity checking  for  in‐
190              put.
191
192       PARODD If  set, then parity for input and output is odd; otherwise even
193              parity is used.
194
195       HUPCL  Lower modem control lines after last process closes  the  device
196              (hang up).
197
198       CLOCAL Ignore modem control lines.
199
200       LOBLK  (not  in POSIX) Block output from a noncurrent shell layer.  For
201              use by shl (shell layers).  (Not implemented on Linux.)
202
203       CIBAUD (not in POSIX) Mask for input speeds.  The values for the CIBAUD
204              bits are the same as the values for the CBAUD bits, shifted left
205              IBSHIFT bits.  [requires _BSD_SOURCE or _SVID_SOURCE]  (Not  im‐
206              plemented  in  glibc,  supported  on Linux via TCGET* and TCSET*
207              ioctls; see ioctl_tty(2))
208
209       CMSPAR (not in POSIX) Use "stick"  (mark/space)  parity  (supported  on
210              certain serial devices): if PARODD is set, the parity bit is al‐
211              ways 1; if PARODD is not set, then the parity bit is  always  0.
212              [requires _BSD_SOURCE or _SVID_SOURCE]
213
214       CRTSCTS
215              (not  in  POSIX)  Enable  RTS/CTS (hardware) flow control.  [re‐
216              quires _BSD_SOURCE or _SVID_SOURCE]
217
218       c_lflag flag constants:
219
220       ISIG   When any of the characters INTR, QUIT, SUSP, or  DSUSP  are  re‐
221              ceived, generate the corresponding signal.
222
223       ICANON Enable canonical mode (described below).
224
225       XCASE  (not in POSIX; not supported under Linux) If ICANON is also set,
226              terminal is uppercase only.  Input is  converted  to  lowercase,
227              except for characters preceded by \.  On output, uppercase char‐
228              acters are preceded by \ and lowercase characters are  converted
229              to   uppercase.    [requires   _BSD_SOURCE  or  _SVID_SOURCE  or
230              _XOPEN_SOURCE]
231
232       ECHO   Echo input characters.
233
234       ECHOE  If ICANON is also set, the ERASE character erases the  preceding
235              input character, and WERASE erases the preceding word.
236
237       ECHOK  If  ICANON  is  also  set, the KILL character erases the current
238              line.
239
240       ECHONL If ICANON is also set, echo the NL character even if ECHO is not
241              set.
242
243       ECHOCTL
244              (not  in POSIX) If ECHO is also set, terminal special characters
245              other than TAB, NL, START, and STOP are echoed as ^X, where X is
246              the  character  with  ASCII  code  0x40 greater than the special
247              character.  For example, character 0x08 (BS) is  echoed  as  ^H.
248              [requires _BSD_SOURCE or _SVID_SOURCE]
249
250       ECHOPRT
251              (not  in  POSIX) If ICANON and ECHO are also set, characters are
252              printed as they are  being  erased.   [requires  _BSD_SOURCE  or
253              _SVID_SOURCE]
254
255       ECHOKE (not  in POSIX) If ICANON is also set, KILL is echoed by erasing
256              each character on the line, as specified by ECHOE  and  ECHOPRT.
257              [requires _BSD_SOURCE or _SVID_SOURCE]
258
259       DEFECHO
260              (not in POSIX) Echo only when a process is reading.  (Not imple‐
261              mented on Linux.)
262
263       FLUSHO (not in POSIX;  not  supported  under  Linux)  Output  is  being
264              flushed.   This flag is toggled by typing the DISCARD character.
265              [requires _BSD_SOURCE or _SVID_SOURCE]
266
267       NOFLSH Disable flushing the input and  output  queues  when  generating
268              signals for the INT, QUIT, and SUSP characters.
269
270       TOSTOP Send  the  SIGTTOU  signal  to the process group of a background
271              process which tries to write to its controlling terminal.
272
273       PENDIN (not in POSIX; not supported under Linux) All characters in  the
274              input  queue  are  reprinted  when  the  next character is read.
275              (bash(1) handles typeahead this way.)  [requires _BSD_SOURCE  or
276              _SVID_SOURCE]
277
278       IEXTEN Enable  implementation-defined  input processing.  This flag, as
279              well as ICANON must be enabled for the special characters  EOL2,
280              LNEXT, REPRINT, WERASE to be interpreted, and for the IUCLC flag
281              to be effective.
282
283       The c_cc array defines the terminal special characters.   The  symbolic
284       indices (initial values) and meaning are:
285
286       VDISCARD
287              (not  in POSIX; not supported under Linux; 017, SI, Ctrl-O) Tog‐
288              gle: start/stop discarding pending output.  Recognized when IEX‐
289              TEN is set, and then not passed as input.
290
291       VDSUSP (not  in  POSIX; not supported under Linux; 031, EM, Ctrl-Y) De‐
292              layed suspend character (DSUSP): send SIGTSTP  signal  when  the
293              character  is  read by the user program.  Recognized when IEXTEN
294              and ISIG are set, and the system supports job control, and  then
295              not passed as input.
296
297       VEOF   (004, EOT, Ctrl-D) End-of-file character (EOF).  More precisely:
298              this character causes the pending tty buffer to be sent  to  the
299              waiting  user program without waiting for end-of-line.  If it is
300              the first character of the line, the read(2) in the user program
301              returns  0, which signifies end-of-file.  Recognized when ICANON
302              is set, and then not passed as input.
303
304       VEOL   (0, NUL) Additional  end-of-line  character  (EOL).   Recognized
305              when ICANON is set.
306
307       VEOL2  (not in POSIX; 0, NUL) Yet another end-of-line character (EOL2).
308              Recognized when ICANON is set.
309
310       VERASE (0177, DEL, rubout, or 010, BS, Ctrl-H, or also #) Erase charac‐
311              ter (ERASE).  This erases the previous not-yet-erased character,
312              but does not erase past EOF  or  beginning-of-line.   Recognized
313              when ICANON is set, and then not passed as input.
314
315       VINTR  (003,  ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt charac‐
316              ter (INTR).  Send a SIGINT signal.  Recognized when ISIG is set,
317              and then not passed as input.
318
319       VKILL  (025,  NAK, Ctrl-U, or Ctrl-X, or also @) Kill character (KILL).
320              This erases the input since the last EOF  or  beginning-of-line.
321              Recognized when ICANON is set, and then not passed as input.
322
323       VLNEXT (not  in  POSIX; 026, SYN, Ctrl-V) Literal next (LNEXT).  Quotes
324              the next input character, depriving it  of  a  possible  special
325              meaning.   Recognized when IEXTEN is set, and then not passed as
326              input.
327
328       VMIN   Minimum number of characters for noncanonical read (MIN).
329
330       VQUIT  (034, FS, Ctrl-\) Quit character (QUIT).  Send  SIGQUIT  signal.
331              Recognized when ISIG is set, and then not passed as input.
332
333       VREPRINT
334              (not  in POSIX; 022, DC2, Ctrl-R) Reprint unread characters (RE‐
335              PRINT).  Recognized when ICANON and IEXTEN are set, and then not
336              passed as input.
337
338       VSTART (021,  DC1,  Ctrl-Q)  Start  character (START).  Restarts output
339              stopped by the Stop character.  Recognized when IXON is set, and
340              then not passed as input.
341
342       VSTATUS
343              (not  in  POSIX; not supported under Linux; status request: 024,
344              DC4, Ctrl-T).  Status character (STATUS).  Display status infor‐
345              mation  at  terminal,  including state of foreground process and
346              amount of CPU time it has consumed.  Also sends a SIGINFO signal
347              (not supported on Linux) to the foreground process group.
348
349       VSTOP  (023,  DC3,  Ctrl-S)  Stop  character (STOP).  Stop output until
350              Start character typed.  Recognized when IXON is  set,  and  then
351              not passed as input.
352
353       VSUSP  (032,  SUB, Ctrl-Z) Suspend character (SUSP).  Send SIGTSTP sig‐
354              nal.  Recognized when ISIG is set, and then not passed as input.
355
356       VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch charac‐
357              ter (SWTCH).  Used in System V to switch shells in shell layers,
358              a predecessor to shell job control.
359
360       VTIME  Timeout in deciseconds for noncanonical read (TIME).
361
362       VWERASE
363              (not in POSIX; 027, ETB, Ctrl-W) Word  erase  (WERASE).   Recog‐
364              nized when ICANON and IEXTEN are set, and then not passed as in‐
365              put.
366
367       An individual terminal special character can be disabled by setting the
368       value of the corresponding c_cc element to _POSIX_VDISABLE.
369
370       The  above  symbolic  subscript  values  are all different, except that
371       VTIME, VMIN may have the same value as VEOL,  VEOF,  respectively.   In
372       noncanonical  mode  the  special  character  meaning is replaced by the
373       timeout meaning.  For an explanation of VMIN and  VTIME,  see  the  de‐
374       scription of noncanonical mode below.
375
376   Retrieving and changing terminal settings
377       tcgetattr()  gets the parameters associated with the object referred by
378       fd and stores them in the termios structure  referenced  by  termios_p.
379       This  function  may  be invoked from a background process; however, the
380       terminal  attributes  may  be  subsequently  changed  by  a  foreground
381       process.
382
383       tcsetattr()  sets  the  parameters associated with the terminal (unless
384       support is required from the underlying hardware that is not available)
385       from  the termios structure referred to by termios_p.  optional_actions
386       specifies when the changes take effect:
387
388       TCSANOW
389              the change occurs immediately.
390
391       TCSADRAIN
392              the change occurs after all output written to fd has been trans‐
393              mitted.   This  option  should  be used when changing parameters
394              that affect output.
395
396       TCSAFLUSH
397              the change occurs after all output written  to  the  object  re‐
398              ferred  by  fd has been transmitted, and all input that has been
399              received but not read will be discarded  before  the  change  is
400              made.
401
402   Canonical and noncanonical mode
403       The  setting of the ICANON canon flag in c_lflag determines whether the
404       terminal is operating in canonical mode (ICANON  set)  or  noncanonical
405       mode (ICANON unset).  By default, ICANON is set.
406
407       In canonical mode:
408
409       •  Input  is  made  available line by line.  An input line is available
410          when one of the line delimiters is typed (NL, EOL, EOL2; or  EOF  at
411          the  start  of line).  Except in the case of EOF, the line delimiter
412          is included in the buffer returned by read(2).
413
414       •  Line editing is enabled (ERASE, KILL; and if the IEXTEN flag is set:
415          WERASE,  REPRINT, LNEXT).  A read(2) returns at most one line of in‐
416          put; if the read(2) requested fewer bytes than are available in  the
417          current  line  of  input,  then  only as many bytes as requested are
418          read, and the remaining characters will be available  for  a  future
419          read(2).
420
421       •  The  maximum  line  length  is 4096 chars (including the terminating
422          newline character); lines longer than 4096 chars are truncated.  Af‐
423          ter 4095 characters, input processing (e.g., ISIG and ECHO* process‐
424          ing) continues, but any input data after 4095 characters up to  (but
425          not  including)  any terminating newline is discarded.  This ensures
426          that the terminal can always receive more input until at  least  one
427          line can be read.
428
429       In  noncanonical  mode input is available immediately (without the user
430       having to type a line-delimiter character), no input processing is per‐
431       formed, and line editing is disabled.  The read buffer will only accept
432       4095 chars; this provides the necessary space for a newline char if the
433       input  mode is switched to canonical.  The settings of MIN (c_cc[VMIN])
434       and TIME (c_cc[VTIME]) determine the circumstances in which  a  read(2)
435       completes; there are four distinct cases:
436
437       MIN == 0, TIME == 0 (polling read)
438              If  data  is  available,  read(2)  returns immediately, with the
439              lesser of the number of bytes available, or the number of  bytes
440              requested.  If no data is available, read(2) returns 0.
441
442       MIN > 0, TIME == 0 (blocking read)
443              read(2)  blocks until MIN bytes are available, and returns up to
444              the number of bytes requested.
445
446       MIN == 0, TIME > 0 (read with timeout)
447              TIME specifies the limit for a timer in tenths of a second.  The
448              timer is started when read(2) is called.  read(2) returns either
449              when at least one byte of data is available, or when  the  timer
450              expires.  If the timer expires without any input becoming avail‐
451              able, read(2) returns 0.  If data is already  available  at  the
452              time of the call to read(2), the call behaves as though the data
453              was received immediately after the call.
454
455       MIN > 0, TIME > 0 (read with interbyte timeout)
456              TIME specifies the limit for a timer  in  tenths  of  a  second.
457              Once  an  initial  byte of input becomes available, the timer is
458              restarted after each further byte is received.  read(2)  returns
459              when any of the following conditions is met:
460
461              •  MIN bytes have been received.
462
463              •  The interbyte timer expires.
464
465              •  The  number  of bytes requested by read(2) has been received.
466                 (POSIX does not specify this termination  condition,  and  on
467                 some  other  implementations  read(2) does not return in this
468                 case.)
469
470              Because the timer is started only after the initial byte becomes
471              available,  at  least one byte will be read.  If data is already
472              available at the time of the call to read(2), the  call  behaves
473              as though the data was received immediately after the call.
474
475       POSIX  does not specify whether the setting of the O_NONBLOCK file sta‐
476       tus flag takes precedence over the MIN and TIME  settings.   If  O_NON‐
477       BLOCK  is  set,  a read(2) in noncanonical mode may return immediately,
478       regardless of the setting of MIN or TIME.  Furthermore, if no  data  is
479       available,  POSIX  permits a read(2) in noncanonical mode to return ei‐
480       ther 0, or -1 with errno set to EAGAIN.
481
482   Raw mode
483       cfmakeraw() sets the terminal to something like the "raw" mode  of  the
484       old  Version 7 terminal driver: input is available character by charac‐
485       ter, echoing is disabled, and all special processing of terminal  input
486       and  output characters is disabled.  The terminal attributes are set as
487       follows:
488
489           termios_p->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
490                           | INLCR | IGNCR | ICRNL | IXON);
491           termios_p->c_oflag &= ~OPOST;
492           termios_p->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
493           termios_p->c_cflag &= ~(CSIZE | PARENB);
494           termios_p->c_cflag |= CS8;
495
496   Line control
497       tcsendbreak() transmits a continuous stream of zero-valued bits  for  a
498       specific  duration,  if  the terminal is using asynchronous serial data
499       transmission.  If duration is zero, it transmits zero-valued  bits  for
500       at  least  0.25 seconds, and not more than 0.5 seconds.  If duration is
501       not zero, it sends zero-valued  bits  for  some  implementation-defined
502       length of time.
503
504       If the terminal is not using asynchronous serial data transmission, tc‐
505       sendbreak() returns without taking any action.
506
507       tcdrain() waits until all output written to the object referred  to  by
508       fd has been transmitted.
509
510       tcflush() discards data written to the object referred to by fd but not
511       transmitted, or data received but not read, depending on the  value  of
512       queue_selector:
513
514       TCIFLUSH
515              flushes data received but not read.
516
517       TCOFLUSH
518              flushes data written but not transmitted.
519
520       TCIOFLUSH
521              flushes  both  data  received but not read, and data written but
522              not transmitted.
523
524       tcflow() suspends transmission or reception of data on the  object  re‐
525       ferred to by fd, depending on the value of action:
526
527       TCOOFF suspends output.
528
529       TCOON  restarts suspended output.
530
531       TCIOFF transmits a STOP character, which stops the terminal device from
532              transmitting data to the system.
533
534       TCION  transmits a START character, which starts  the  terminal  device
535              transmitting data to the system.
536
537       The  default  on  open of a terminal file is that neither its input nor
538       its output is suspended.
539
540   Line speed
541       The baud rate functions are provided for getting and setting the values
542       of  the  input and output baud rates in the termios structure.  The new
543       values do not take effect until tcsetattr() is successfully called.
544
545       Setting the speed to B0 instructs the modem to "hang up".   The  actual
546       bit rate corresponding to B38400 may be altered with setserial(8).
547
548       The input and output baud rates are stored in the termios structure.
549
550       cfgetospeed() returns the output baud rate stored in the termios struc‐
551       ture pointed to by termios_p.
552
553       cfsetospeed() sets the output baud rate stored in the termios structure
554       pointed to by termios_p to speed, which must be one of these constants:
555
556              B0
557              B50
558              B75
559              B110
560              B134
561              B150
562              B200
563              B300
564              B600
565              B1200
566              B1800
567              B2400
568              B4800
569              B9600
570              B19200
571              B38400
572              B57600
573              B115200
574              B230400
575              B460800
576              B500000
577              B576000
578              B921600
579              B1000000
580              B1152000
581              B1500000
582              B2000000
583
584       These constants are additionally supported on the SPARC architecture:
585
586              B76800
587              B153600
588              B307200
589              B614400
590
591       These constants are additionally supported on non-SPARC architectures:
592
593              B2500000
594              B3000000
595              B3500000
596              B4000000
597
598       Due  to differences between architectures, portable applications should
599       check if a particular Bnnn constant is defined prior to using it.
600
601       The zero baud rate, B0, is used to terminate the connection.  If B0  is
602       specified,  the  modem control lines shall no longer be asserted.  Nor‐
603       mally, this will disconnect the line.  CBAUDEX is a mask for the speeds
604       beyond  those  defined  in  POSIX.1  (57600 and above).  Thus, B57600 &
605       CBAUDEX is nonzero.
606
607       Setting the baud rate to a value other than those defined by Bnnn  con‐
608       stants is possible via the TCSETS2 ioctl; see ioctl_tty(2).
609
610       cfgetispeed()  returns the input baud rate stored in the termios struc‐
611       ture.
612
613       cfsetispeed() sets the input baud rate stored in the termios  structure
614       to  speed,  which must be specified as one of the Bnnn constants listed
615       above for cfsetospeed().  If the input baud rate is set to the  literal
616       constant  0 (not the symbolic constant B0), the input baud rate will be
617       equal to the output baud rate.
618
619       cfsetspeed() is a 4.4BSD extension.  It takes the same arguments as cf‐
620       setispeed(), and sets both input and output speed.
621

RETURN VALUE

623       cfgetispeed()  returns the input baud rate stored in the termios struc‐
624       ture.
625
626       cfgetospeed() returns the output baud rate stored in the termios struc‐
627       ture.
628
629       All other functions return:
630
631       0      on success.
632
633       -1     on failure and set errno to indicate the error.
634
635       Note  that  tcsetattr() returns success if any of the requested changes
636       could be successfully carried out.   Therefore,  when  making  multiple
637       changes  it may be necessary to follow this call with a further call to
638       tcgetattr() to check that all changes have been performed successfully.
639

ATTRIBUTES

641       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
642       tributes(7).
643
644       ┌────────────────────────────────────────────┬───────────────┬─────────┐
645Interface                                   Attribute     Value   
646       ├────────────────────────────────────────────┼───────────────┼─────────┤
647tcgetattr(), tcsetattr(), tcdrain(),        │ Thread safety │ MT-Safe │
648tcflush(), tcflow(), tcsendbreak(),         │               │         │
649cfmakeraw(), cfgetispeed(), cfgetospeed(),  │               │         │
650cfsetispeed(), cfsetospeed(), cfsetspeed()  │               │         │
651       └────────────────────────────────────────────┴───────────────┴─────────┘
652

STANDARDS

654       tcgetattr()
655       tcsetattr()
656       tcsendbreak()
657       tcdrain()
658       tcflush()
659       tcflow()
660       cfgetispeed()
661       cfgetospeed()
662       cfsetispeed()
663       cfsetospeed()
664              POSIX.1-2008.
665
666       cfmakeraw()
667       cfsetspeed()
668              BSD.
669

HISTORY

671       tcgetattr()
672       tcsetattr()
673       tcsendbreak()
674       tcdrain()
675       tcflush()
676       tcflow()
677       cfgetispeed()
678       cfgetospeed()
679       cfsetispeed()
680       cfsetospeed()
681              POSIX.1-2001.
682
683       cfmakeraw()
684       cfsetspeed()
685              BSD.
686

NOTES

688       UNIX V7 and several later systems have a list of baud rates where after
689       the  values  B0  through  B9600  one finds the two constants EXTA, EXTB
690       ("External A" and "External B").  Many systems  extend  the  list  with
691       much higher baud rates.
692
693       The  effect  of  a  nonzero  duration with tcsendbreak() varies.  SunOS
694       specifies a break of duration * N seconds, where N is  at  least  0.25,
695       and  not more than 0.5.  Linux, AIX, DU, Tru64 send a break of duration
696       milliseconds.  FreeBSD and NetBSD and HP-UX and MacOS ignore the  value
697       of  duration.   Under  Solaris and UnixWare, tcsendbreak() with nonzero
698       duration behaves like tcdrain().
699

BUGS

701       On the Alpha architecture before Linux 4.16  (and  glibc  before  glibc
702       2.28),  the  XTABS  value was different from TAB3 and it was ignored by
703       the N_TTY line discipline code of  the  terminal  driver  as  a  result
704       (because as it wasn't part of the TABDLY mask).
705

SEE ALSO

707       reset(1),    setterm(1),    stty(1),    tput(1),    tset(1),    tty(1),
708       ioctl_console(2),    ioctl_tty(2),     cc_t(3type),     speed_t(3type),
709       tcflag_t(3type), setserial(8)
710
711
712
713Linux man-pages 6.05              2023-07-30                        termios(3)
Impressum