1 .\" Hey Emacs! This file is -*- nroff -*- source.
3 .\" Copyright (c) 1993 Michael Haardt
5 .\" Fri Apr 2 11:32:09 MET DST 1993
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27 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
28 .\" Modified 1995-02-25 by Jim Van Zandt <jrv@vanzandt.mv.com>
29 .\" Modified 1995-09-02 by Jim Van Zandt <jrv@vanzandt.mv.com>
30 .\" moved to man3, aeb, 950919
31 .\" Modified 2001-09-22 by Michael Kerrisk <mtk.manpages@gmail.com>
32 .\" Modified 2001-12-17, aeb
33 .\" Modified 2004-10-31, aeb
35 .\" Added .SS headers to give some structure to this page; and a
36 .\" small amount of reordering.
37 .\" Added a section on canonical and noncanonical mode.
38 .\" Enhanced the discussion of "raw" mode for cfmakeraw().
41 .TH TERMIOS 3 2011-09-08 "Linux" "Linux Programmer's Manual"
43 termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow,
44 cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, cfsetspeed \-
45 get and set terminal attributes, line control, get and set baud rate
48 .B #include <termios.h>
50 .B #include <unistd.h>
52 .BI "int tcgetattr(int " fd ", struct termios *" termios_p );
54 .BI "int tcsetattr(int " fd ", int " optional_actions ,
55 .BI " const struct termios *" termios_p );
57 .BI "int tcsendbreak(int " fd ", int " duration );
59 .BI "int tcdrain(int " fd );
61 .BI "int tcflush(int " fd ", int " queue_selector );
63 .BI "int tcflow(int " fd ", int " action );
65 .BI "void cfmakeraw(struct termios *" termios_p );
67 .BI "speed_t cfgetispeed(const struct termios *" termios_p );
69 .BI "speed_t cfgetospeed(const struct termios *" termios_p );
71 .BI "int cfsetispeed(struct termios *" termios_p ", speed_t " speed );
73 .BI "int cfsetospeed(struct termios *" termios_p ", speed_t " speed );
75 .BI "int cfsetspeed(struct termios *" termios_p ", speed_t " speed );
79 Feature Test Macro Requirements for glibc (see
80 .BR feature_test_macros (7)):
87 The termios functions describe a general terminal interface that is
88 provided to control asynchronous communications ports.
89 .SS "The termios structure"
91 Many of the functions described here have a \fItermios_p\fP argument
92 that is a pointer to a \fItermios\fP structure.
93 This structure contains at least the following members:
97 tcflag_t c_iflag; /* input modes */
98 tcflag_t c_oflag; /* output modes */
99 tcflag_t c_cflag; /* control modes */
100 tcflag_t c_lflag; /* local modes */
101 cc_t c_cc[NCCS]; /* special characters */
105 The values that may be assigned to these fields are described below.
106 In the case of the first four bit-mask fields,
107 the definitions of some of the associated flags that may be set are
108 only exposed if a specific feature test macro (see
109 .BR feature_test_macros (7))
110 is defined, as noted in brackets ("[]").
112 In the descriptions below, "not in POSIX" means that the
113 value is not specified in POSIX.1-2001,
114 and "XSI" means that the value is specified in POSIX.1-2001
115 as part of the XSI extension.
117 \fIc_iflag\fP flag constants:
120 Ignore BREAK condition on input.
123 If \fBIGNBRK\fP is set, a BREAK is ignored.
125 but \fBBRKINT\fP is set, then a BREAK causes the input and output
126 queues to be flushed, and if the terminal is the controlling
127 terminal of a foreground process group, it will cause a
128 \fBSIGINT\fP to be sent to this foreground process group.
129 When neither \fBIGNBRK\fP nor \fBBRKINT\fP are set, a BREAK
130 reads as a null byte (\(aq\\0\(aq), except when \fBPARMRK\fP is set,
131 in which case it reads as the sequence \\377 \\0 \\0.
134 Ignore framing errors and parity errors.
137 If \fBIGNPAR\fP is not set, prefix a character with a parity error or
138 framing error with \\377 \\0.
139 If neither \fBIGNPAR\fP nor \fBPARMRK\fP
140 is set, read a character with a parity error or framing error
144 Enable input parity checking.
147 Strip off eighth bit.
150 Translate NL to CR on input.
153 Ignore carriage return on input.
156 Translate carriage return to newline on input (unless \fBIGNCR\fP is set).
159 (not in POSIX) Map uppercase characters to lowercase on input.
162 Enable XON/XOFF flow control on output.
165 (XSI) Typing any character will restart stopped output.
166 (The default is to allow just the START character to restart output.)
169 Enable XON/XOFF flow control on input.
172 (not in POSIX) Ring bell when input queue is full.
173 Linux does not implement this bit, and acts as if it is always set.
175 .BR IUTF8 " (since Linux 2.6.4)"
176 (not in POSIX) Input is UTF8;
177 this allows character-erase to be correctly performed in cooked mode.
179 \fIc_oflag\fP flag constants defined in POSIX.1:
182 Enable implementation-defined output processing.
184 The remaining \fIc_oflag\fP flag constants are defined in POSIX.1-2001,
185 unless marked otherwise.
188 (not in POSIX) Map lowercase characters to uppercase on output.
191 (XSI) Map NL to CR-NL on output.
194 Map CR to NL on output.
197 Don't output CR at column 0.
203 Send fill characters for a delay, rather than using a timed delay.
206 (not in POSIX) Fill character is ASCII DEL (0177).
207 If unset, fill character is ASCII NUL (\(aq\\0\(aq).
208 (Not implemented on Linux.)
212 Values are \fBNL0\fP and \fBNL1\fP.
221 Carriage return delay mask.
222 Values are \fBCR0\fP, \fBCR1\fP, \fBCR2\fP, or \fBCR3\fP.
231 Horizontal tab delay mask.
232 Values are \fBTAB0\fP, \fBTAB1\fP, \fBTAB2\fP, \fBTAB3\fP (or \fBXTABS\fP).
233 A value of TAB3, that is, XTABS, expands tabs to spaces
234 (with tab stops every eight columns).
243 Backspace delay mask.
244 Values are \fBBS0\fP or \fBBS1\fP.
245 (Has never been implemented.)
254 Vertical tab delay mask.
255 Values are \fBVT0\fP or \fBVT1\fP.
258 Form feed delay mask.
259 Values are \fBFF0\fP or \fBFF1\fP.
267 \fIc_cflag\fP flag constants:
270 (not in POSIX) Baud speed mask (4+1 bits).
277 (not in POSIX) Extra baud speed mask (1 bit), included in
284 (POSIX says that the baud speed is stored in the
286 structure without specifying where precisely, and provides
291 Some systems use bits selected by
295 other systems use separate fields, for example,
302 Values are \fBCS5\fP, \fBCS6\fP, \fBCS7\fP, or \fBCS8\fP.
305 Set two stop bits, rather than one.
311 Enable parity generation on output and parity checking for input.
314 If set, then parity for input and output is odd;
315 otherwise even parity is used.
318 Lower modem control lines after last process closes the device (hang up).
321 Ignore modem control lines.
324 (not in POSIX) Block output from a noncurrent shell layer.
325 For use by \fBshl\fP (shell layers). (Not implemented on Linux.)
328 (not in POSIX) Mask for input speeds.
332 the same as the values for the
341 (Not implemented on Linux.)
345 Use "stick" (mark/space) parity (supported on certain serial
348 is set, the parity bit is always 1; if
350 is not set, then the parity bit is always 0).
357 (not in POSIX) Enable RTS/CTS (hardware) flow control.
363 \fIc_lflag\fP flag constants:
366 When any of the characters INTR, QUIT, SUSP, or DSUSP are received,
367 generate the corresponding signal.
370 Enable canonical mode (described below).
373 (not in POSIX; not supported under Linux)
374 If \fBICANON\fP is also set, terminal is uppercase only.
375 Input is converted to lowercase, except for characters preceded by \\.
376 On output, uppercase characters are preceded by \\ and lowercase
377 characters are converted to uppercase.
378 [requires _BSD_SOURCE or _SVID_SOURCE or _XOPEN_SOURCE]
379 .\" glibc is probably now wrong to allow
386 Echo input characters.
389 If \fBICANON\fP is also set, the ERASE character erases the preceding
390 input character, and WERASE erases the preceding word.
393 If \fBICANON\fP is also set, the KILL character erases the current line.
396 If \fBICANON\fP is also set, echo the NL character even if ECHO is not set.
399 (not in POSIX) If \fBECHO\fP is also set,
400 terminal special characters other than
401 TAB, NL, START, and STOP are echoed as \fB^X\fP,
402 where X is the character with
403 ASCII code 0x40 greater than the special character.
404 For example, character
405 0x08 (BS) is echoed as \fB^H\fP.
412 (not in POSIX) If \fBICANON\fP and \fBECHO\fP are also set, characters
413 are printed as they are being erased.
420 (not in POSIX) If \fBICANON\fP is also set, KILL is echoed by erasing
421 each character on the line, as specified by \fBECHOE\fP and \fBECHOPRT\fP.
428 (not in POSIX) Echo only when a process is reading.
429 (Not implemented on Linux.)
432 (not in POSIX; not supported under Linux)
433 Output is being flushed.
434 This flag is toggled by typing
435 the DISCARD character.
442 Disable flushing the input and output queues when generating signals for the
443 INT, QUIT, and SUSP characters.
444 .\" Stevens lets SUSP only flush the input queue
449 signal to the process group of a background process
450 which tries to write to its controlling terminal.
453 (not in POSIX; not supported under Linux)
454 All characters in the input queue are reprinted when
455 the next character is read.
457 handles typeahead this way.)
464 Enable implementation-defined input processing.
465 This flag, as well as \fBICANON\fP must be enabled for the
466 special characters EOL2, LNEXT, REPRINT, WERASE to be interpreted,
467 and for the \fBIUCLC\fP flag to be effective.
469 The \fIc_cc\fP array defines the terminal special characters.
470 The symbolic indices (initial values) and meaning are:
473 (not in POSIX; not supported under Linux; 017, SI, Ctrl-O)
474 Toggle: start/stop discarding pending output.
477 is set, and then not passed as input.
480 (not in POSIX; not supported under Linux; 031, EM, Ctrl-Y)
481 Delayed suspend character (DSUSP):
484 signal when the character is read by the user program.
489 are set, and the system supports
490 job control, and then not passed as input.
494 End-of-file character (EOF).
495 More precisely: this character causes the pending tty buffer to be sent
496 to the waiting user program without waiting for end-of-line.
497 If it is the first character of the line, the
499 in the user program returns 0, which signifies end-of-file.
502 is set, and then not passed as input.
506 Additional end-of-line character (EOL).
512 (not in POSIX; 0, NUL)
513 Yet another end-of-line character (EOL2).
519 (0177, DEL, rubout, or 010, BS, Ctrl-H, or also #)
520 Erase character (ERASE).
521 This erases the previous not-yet-erased character,
522 but does not erase past EOF or beginning-of-line.
525 is set, and then not passed as input.
528 (003, ETX, Ctrl-C, or also 0177, DEL, rubout)
529 Interrupt character (INTR).
535 is set, and then not passed as input.
538 (025, NAK, Ctrl-U, or Ctrl-X, or also @)
539 Kill character (KILL).
540 This erases the input since the last EOF or beginning-of-line.
543 is set, and then not passed as input.
546 (not in POSIX; 026, SYN, Ctrl-V)
547 Literal next (LNEXT).
548 Quotes the next input character, depriving it of
549 a possible special meaning.
552 is set, and then not passed as input.
555 Minimum number of characters for noncanonical read (MIN).
559 Quit character (QUIT).
565 is set, and then not passed as input.
568 (not in POSIX; 022, DC2, Ctrl-R)
569 Reprint unread characters (REPRINT).
574 are set, and then not passed as input.
578 Start character (START).
579 Restarts output stopped by the Stop character.
582 is set, and then not passed as input.
585 (not in POSIX; not supported under Linux;
586 status request: 024, DC4, Ctrl-T).
587 Status character (STATUS).
588 Display status information at terminal,
589 including state of foreground process and amount of CPU time it has consumed.
592 signal (not supported on Linux) to the foreground process group.
596 Stop character (STOP).
597 Stop output until Start character typed.
600 is set, and then not passed as input.
604 Suspend character (SUSP).
610 is set, and then not passed as input.
613 (not in POSIX; not supported under Linux; 0, NUL)
614 Switch character (SWTCH).
615 Used in System V to switch shells in
617 a predecessor to shell job control.
620 Timeout in deciseconds for noncanonical read (TIME).
623 (not in POSIX; 027, ETB, Ctrl-W)
629 are set, and then not passed as input.
631 An individual terminal special character can be disabled by setting
632 the value of the corresponding
635 .BR _POSIX_VDISABLE .
637 The above symbolic subscript values are all different, except that
640 may have the same value as
644 In noncanonical mode the special character meaning is replaced
645 by the timeout meaning.
646 For an explanation of
650 see the description of
651 noncanonical mode below.
652 .SS "Retrieving and changing terminal settings"
655 gets the parameters associated with the object referred by \fIfd\fP and
656 stores them in the \fItermios\fP structure referenced by
658 This function may be invoked from a background process;
659 however, the terminal attributes may be subsequently changed by a
663 sets the parameters associated with the terminal (unless support is
664 required from the underlying hardware that is not available) from the
665 \fItermios\fP structure referred to by \fItermios_p\fP.
666 \fIoptional_actions\fP specifies when the changes take effect:
668 the change occurs immediately.
670 the change occurs after all output written to
672 has been transmitted.
673 This function should be used when changing
674 parameters that affect output.
676 the change occurs after all output written to the object referred by
678 has been transmitted, and all input that has been received but not read
679 will be discarded before the change is made.
680 .SS "Canonical and noncanonical mode"
685 determines whether the terminal is operating in canonical mode
697 Input is made available line by line.
698 An input line is available when one of the line delimiters
699 is typed (NL, EOL, EOL2; or EOF at the start of line).
700 Except in the case of EOF, the line delimiter is included
701 in the buffer returned by
704 Line editing is enabled (ERASE, KILL;
707 flag is set: WERASE, REPRINT, LNEXT).
710 returns at most one line of input; if the
712 requested fewer bytes than are available in the current line of input,
713 then only as many bytes as requested are read,
714 and the remaining characters will be available for a future
717 In noncanonical mode input is available immediately (without
718 the user having to type a line-delimiter character),
719 and line editing is disabled.
724 determine the circumstances in which a
726 completes; there are four distinct cases:
729 If data is available,
731 returns immediately, with the lesser of the number of bytes
732 available, or the number of bytes requested.
733 If no data is available,
739 blocks until the lesser of MIN bytes or the number of bytes requested
740 are available, and returns the lesser of these two values.
743 TIME specifies the limit for a timer in tenths of a second.
744 The timer is started when
748 returns either when at least one byte of data is available,
749 or when the timer expires.
750 If the timer expires without any input becoming available,
755 TIME specifies the limit for a timer in tenths of a second.
756 Once an initial byte of input becomes available,
757 the timer is restarted after each further byte is received.
759 returns either when the lesser of the number of bytes requested or
760 MIN byte have been read,
761 or when the inter-byte timeout expires.
762 Because the timer is only started after the initial byte
763 becomes available, at least one byte will be read.
767 sets the terminal to something like the
768 "raw" mode of the old Version 7 terminal driver:
769 input is available character by character,
770 echoing is disabled, and all special processing of
771 terminal input and output characters is disabled.
772 The terminal attributes are set as follows:
775 termios_p\->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
776 | INLCR | IGNCR | ICRNL | IXON);
777 termios_p\->c_oflag &= ~OPOST;
778 termios_p\->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
779 termios_p\->c_cflag &= ~(CSIZE | PARENB);
780 termios_p\->c_cflag |= CS8;
785 transmits a continuous stream of zero-valued bits for a specific
786 duration, if the terminal is using asynchronous serial data
788 If \fIduration\fP is zero, it transmits zero-valued bits
789 for at least 0.25 seconds, and not more that 0.5 seconds.
790 If \fIduration\fP is not zero, it sends zero-valued bits for some
791 implementation-defined length of time.
793 If the terminal is not using asynchronous serial data transmission,
795 returns without taking any action.
798 waits until all output written to the object referred to by
800 has been transmitted.
803 discards data written to the object referred to by
805 but not transmitted, or data received but not read, depending on the
809 flushes data received but not read.
811 flushes data written but not transmitted.
813 flushes both data received but not read, and data written but not
817 suspends transmission or reception of data on the object referred to by
819 depending on the value of
824 restarts suspended output.
826 transmits a STOP character, which stops the terminal device from
827 transmitting data to the system.
829 transmits a START character, which starts the terminal device
830 transmitting data to the system.
832 The default on open of a terminal file is that neither its input nor its
835 The baud rate functions are provided for getting and setting the values
836 of the input and output baud rates in the \fItermios\fP structure.
837 The new values do not take effect
840 is successfully called.
842 Setting the speed to \fBB0\fP instructs the modem to "hang up".
843 The actual bit rate corresponding to \fBB38400\fP may be altered with
846 The input and output baud rates are stored in the \fItermios\fP
850 returns the output baud rate stored in the \fItermios\fP structure
855 sets the output baud rate stored in the \fItermios\fP structure pointed
856 to by \fItermios_p\fP to \fIspeed\fP, which must be one of these constants:
882 The zero baud rate, \fBB0\fP,
883 is used to terminate the connection.
884 If B0 is specified, the modem control lines shall no longer be asserted.
885 Normally, this will disconnect the line.
886 \fBCBAUDEX\fP is a mask
887 for the speeds beyond those defined in POSIX.1 (57600 and above).
888 Thus, \fBB57600\fP & \fBCBAUDEX\fP is nonzero.
891 returns the input baud rate stored in the \fItermios\fP structure.
894 sets the input baud rate stored in the \fItermios\fP structure to
896 which must be specified as one of the \fBBnnn\fP constants listed above for
898 If the input baud rate is set to zero, the input baud rate will be
899 equal to the output baud rate.
902 is a 4.4BSD extension.
903 It takes the same arguments as
905 and sets both input and output speed.
909 returns the input baud rate stored in the
914 returns the output baud rate stored in the \fItermios\fP structure.
916 All other functions return:
922 to indicate the error.
926 returns success if \fIany\fP of the requested changes could be
927 successfully carried out.
928 Therefore, when making multiple changes
929 it may be necessary to follow this call with a further call to
931 to check that all changes have been performed successfully.
944 are specified in POSIX.1-2001.
949 are nonstandard, but available on the BSDs.
951 UNIX V7 and several later systems have a list of baud rates
952 where after the fourteen values B0, ..., B9600 one finds the
953 two constants EXTA, EXTB ("External A" and "External B").
954 Many systems extend the list with much higher baud rates.
956 The effect of a nonzero \fIduration\fP with
959 SunOS specifies a break of
961 seconds, where \fIN\fP is at least 0.25, and not more than 0.5.
962 Linux, AIX, DU, Tru64 send a break of
965 FreeBSD and NetBSD and HP-UX and MacOS ignore the value of
967 Under Solaris and UnixWare,
973 .\" libc4 until 4.7.5, glibc for sysv: EINVAL for duration > 0.
974 .\" libc4.7.6, libc5, glibc for unix: duration in ms.
975 .\" glibc for bsd: duration in us
976 .\" glibc for sunos4: ignore duration
979 .BR console_ioctl (4),
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