'\" t .\" Copyright (c) 1993 Michael Haardt (michael@moria.de) .\" Fri Apr 2 11:32:09 MET DST 1993 .\" Copyright (c) 2006-2015, Michael Kerrisk .\" .\" SPDX-License-Identifier: GPL-2.0-or-later .\" .\" Modified 1993-07-24 by Rik Faith .\" Modified 1995-02-25 by Jim Van Zandt .\" Modified 1995-09-02 by Jim Van Zandt .\" moved to man3, aeb, 950919 .\" Modified 2001-09-22 by Michael Kerrisk .\" Modified 2001-12-17, aeb .\" Modified 2004-10-31, aeb .\" 2006-12-28, mtk: .\" Added .SS headers to give some structure to this page; and a .\" small amount of reordering. .\" Added a section on canonical and noncanonical mode. .\" Enhanced the discussion of "raw" mode for cfmakeraw(). .\" Document CMSPAR. .\" .TH termios 3 2023-10-31 "Linux man-pages 6.06" .SH NAME termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow, cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, cfsetspeed \- get and set terminal attributes, line control, get and set baud rate .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .B #include .P .BI "int tcgetattr(int " fd ", struct termios *" termios_p ); .BI "int tcsetattr(int " fd ", int " optional_actions , .BI " const struct termios *" termios_p ); .P .BI "int tcsendbreak(int " fd ", int " duration ); .BI "int tcdrain(int " fd ); .BI "int tcflush(int " fd ", int " queue_selector ); .BI "int tcflow(int " fd ", int " action ); .P .BI "void cfmakeraw(struct termios *" termios_p ); .P .BI "speed_t cfgetispeed(const struct termios *" termios_p ); .BI "speed_t cfgetospeed(const struct termios *" termios_p ); .P .BI "int cfsetispeed(struct termios *" termios_p ", speed_t " speed ); .BI "int cfsetospeed(struct termios *" termios_p ", speed_t " speed ); .BI "int cfsetspeed(struct termios *" termios_p ", speed_t " speed ); .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR cfsetspeed (), .BR cfmakeraw (): .nf Since glibc 2.19: _DEFAULT_SOURCE glibc 2.19 and earlier: _BSD_SOURCE .fi .SH DESCRIPTION The termios functions describe a general terminal interface that is provided to control asynchronous communications ports. .SS The termios structure Many of the functions described here have a \fItermios_p\fP argument that is a pointer to a \fItermios\fP structure. This structure contains at least the following members: .P .in +4n .EX tcflag_t c_iflag; /* input modes */ tcflag_t c_oflag; /* output modes */ tcflag_t c_cflag; /* control modes */ tcflag_t c_lflag; /* local modes */ cc_t c_cc[NCCS]; /* special characters */ .EE .in .P The values that may be assigned to these fields are described below. In the case of the first four bit-mask fields, the definitions of some of the associated flags that may be set are exposed only if a specific feature test macro (see .BR feature_test_macros (7)) is defined, as noted in brackets ("[]"). .P In the descriptions below, "not in POSIX" means that the value is not specified in POSIX.1-2001, and "XSI" means that the value is specified in POSIX.1-2001 as part of the XSI extension. .P \fIc_iflag\fP flag constants: .TP .B IGNBRK Ignore BREAK condition on input. .TP .B BRKINT If \fBIGNBRK\fP is set, a BREAK is ignored. If it is not set but \fBBRKINT\fP is set, then a BREAK causes the input and output queues to be flushed, and if the terminal is the controlling terminal of a foreground process group, it will cause a \fBSIGINT\fP to be sent to this foreground process group. When neither \fBIGNBRK\fP nor \fBBRKINT\fP are set, a BREAK reads as a null byte (\[aq]\e0\[aq]), except when \fBPARMRK\fP is set, in which case it reads as the sequence \e377 \e0 \e0. .TP .B IGNPAR Ignore framing errors and parity errors. .TP .B PARMRK If this bit is set, input bytes with parity or framing errors are marked when passed to the program. This bit is meaningful only when \fBINPCK\fP is set and \fBIGNPAR\fP is not set. The way erroneous bytes are marked is with two preceding bytes, \e377 and \e0. Thus, the program actually reads three bytes for one erroneous byte received from the terminal. If a valid byte has the value \e377, and \fBISTRIP\fP (see below) is not set, the program might confuse it with the prefix that marks a parity error. Therefore, a valid byte \e377 is passed to the program as two bytes, \e377 \e377, in this case. .IP If neither \fBIGNPAR\fP nor \fBPARMRK\fP is set, read a character with a parity error or framing error as \e0. .TP .B INPCK Enable input parity checking. .TP .B ISTRIP Strip off eighth bit. .TP .B INLCR Translate NL to CR on input. .TP .B IGNCR Ignore carriage return on input. .TP .B ICRNL Translate carriage return to newline on input (unless \fBIGNCR\fP is set). .TP .B IUCLC (not in POSIX) Map uppercase characters to lowercase on input. .TP .B IXON Enable XON/XOFF flow control on output. .TP .B IXANY (XSI) Typing any character will restart stopped output. (The default is to allow just the START character to restart output.) .TP .B IXOFF Enable XON/XOFF flow control on input. .TP .B IMAXBEL (not in POSIX) Ring bell when input queue is full. Linux does not implement this bit, and acts as if it is always set. .TP .BR IUTF8 " (since Linux 2.6.4)" (not in POSIX) Input is UTF8; this allows character-erase to be correctly performed in cooked mode. .P .I c_oflag flag constants: .TP .B OPOST Enable implementation-defined output processing. .TP .B OLCUC (not in POSIX) Map lowercase characters to uppercase on output. .TP .B ONLCR (XSI) Map NL to CR-NL on output. .TP .B OCRNL Map CR to NL on output. .TP .B ONOCR Don't output CR at column 0. .TP .B ONLRET The NL character is assumed to do the carriage-return function; the kernel's idea of the current column is set to 0 after both NL and CR. .TP .B OFILL Send fill characters for a delay, rather than using a timed delay. .TP .B OFDEL Fill character is ASCII DEL (0177). If unset, fill character is ASCII NUL (\[aq]\e0\[aq]). (Not implemented on Linux.) .TP .B NLDLY Newline delay mask. Values are \fBNL0\fP and \fBNL1\fP. [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .TP .B CRDLY Carriage return delay mask. Values are \fBCR0\fP, \fBCR1\fP, \fBCR2\fP, or \fBCR3\fP. [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .TP .B TABDLY Horizontal tab delay mask. Values are \fBTAB0\fP, \fBTAB1\fP, \fBTAB2\fP, \fBTAB3\fP (or \fBXTABS\fP, but see the .B BUGS section). A value of TAB3, that is, XTABS, expands tabs to spaces (with tab stops every eight columns). [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .TP .B BSDLY Backspace delay mask. Values are \fBBS0\fP or \fBBS1\fP. (Has never been implemented.) [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .TP .B VTDLY Vertical tab delay mask. Values are \fBVT0\fP or \fBVT1\fP. .TP .B FFDLY Form feed delay mask. Values are \fBFF0\fP or \fBFF1\fP. [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .P \fIc_cflag\fP flag constants: .TP .B CBAUD (not in POSIX) Baud speed mask (4+1 bits). [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B CBAUDEX (not in POSIX) Extra baud speed mask (1 bit), included in .BR CBAUD . [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .IP (POSIX says that the baud speed is stored in the .I termios structure without specifying where precisely, and provides .BR cfgetispeed () and .BR cfsetispeed () for getting at it. Some systems use bits selected by .B CBAUD in .IR c_cflag , other systems use separate fields, for example, .I sg_ispeed and .IR sg_ospeed .) .TP .B CSIZE Character size mask. Values are \fBCS5\fP, \fBCS6\fP, \fBCS7\fP, or \fBCS8\fP. .TP .B CSTOPB Set two stop bits, rather than one. .TP .B CREAD Enable receiver. .TP .B PARENB Enable parity generation on output and parity checking for input. .TP .B PARODD If set, then parity for input and output is odd; otherwise even parity is used. .TP .B HUPCL Lower modem control lines after last process closes the device (hang up). .TP .B CLOCAL Ignore modem control lines. .TP .B LOBLK (not in POSIX) Block output from a noncurrent shell layer. For use by \fBshl\fP (shell layers). (Not implemented on Linux.) .TP .B CIBAUD (not in POSIX) Mask for input speeds. The values for the .B CIBAUD bits are the same as the values for the .B CBAUD bits, shifted left .B IBSHIFT bits. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] (Not implemented in glibc, supported on Linux via .BR TCGET * and .BR TCSET * ioctls; see .BR ioctl_tty (2)) .TP .B CMSPAR (not in POSIX) Use "stick" (mark/space) parity (supported on certain serial devices): if .B PARODD is set, the parity bit is always 1; if .B PARODD is not set, then the parity bit is always 0. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B CRTSCTS (not in POSIX) Enable RTS/CTS (hardware) flow control. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .P \fIc_lflag\fP flag constants: .TP .B ISIG When any of the characters INTR, QUIT, SUSP, or DSUSP are received, generate the corresponding signal. .TP .B ICANON Enable canonical mode (described below). .TP .B XCASE (not in POSIX; not supported under Linux) If \fBICANON\fP is also set, terminal is uppercase only. Input is converted to lowercase, except for characters preceded by \e. On output, uppercase characters are preceded by \e and lowercase characters are converted to uppercase. [requires .B _BSD_SOURCE or .B _SVID_SOURCE or .BR _XOPEN_SOURCE ] .\" glibc is probably now wrong to allow .\" Define .\" .B _XOPEN_SOURCE .\" to expose .\" .BR XCASE . .TP .B ECHO Echo input characters. .TP .B ECHOE If \fBICANON\fP is also set, the ERASE character erases the preceding input character, and WERASE erases the preceding word. .TP .B ECHOK If \fBICANON\fP is also set, the KILL character erases the current line. .TP .B ECHONL If \fBICANON\fP is also set, echo the NL character even if ECHO is not set. .TP .B ECHOCTL (not in POSIX) If \fBECHO\fP is also set, terminal special characters other than TAB, NL, START, and STOP are echoed as \fB\[ha]X\fP, where X is the character with ASCII code 0x40 greater than the special character. For example, character 0x08 (BS) is echoed as \fB\[ha]H\fP. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B ECHOPRT (not in POSIX) If \fBICANON\fP and \fBECHO\fP are also set, characters are printed as they are being erased. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B ECHOKE (not in POSIX) If \fBICANON\fP is also set, KILL is echoed by erasing each character on the line, as specified by \fBECHOE\fP and \fBECHOPRT\fP. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B DEFECHO (not in POSIX) Echo only when a process is reading. (Not implemented on Linux.) .TP .B FLUSHO (not in POSIX; not supported under Linux) Output is being flushed. This flag is toggled by typing the DISCARD character. [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B NOFLSH Disable flushing the input and output queues when generating signals for the INT, QUIT, and SUSP characters. .\" Stevens lets SUSP only flush the input queue .TP .B TOSTOP Send the .B SIGTTOU signal to the process group of a background process which tries to write to its controlling terminal. .TP .B PENDIN (not in POSIX; not supported under Linux) All characters in the input queue are reprinted when the next character is read. .RB ( bash (1) handles typeahead this way.) [requires .B _BSD_SOURCE or .BR _SVID_SOURCE ] .TP .B IEXTEN Enable implementation-defined input processing. This flag, as well as \fBICANON\fP must be enabled for the special characters EOL2, LNEXT, REPRINT, WERASE to be interpreted, and for the \fBIUCLC\fP flag to be effective. .P The \fIc_cc\fP array defines the terminal special characters. The symbolic indices (initial values) and meaning are: .TP .B VDISCARD (not in POSIX; not supported under Linux; 017, SI, Ctrl-O) Toggle: start/stop discarding pending output. Recognized when .B IEXTEN is set, and then not passed as input. .TP .B VDSUSP (not in POSIX; not supported under Linux; 031, EM, Ctrl-Y) Delayed suspend character (DSUSP): send .B SIGTSTP signal when the character is read by the user program. Recognized when .B IEXTEN and .B ISIG are set, and the system supports job control, and then not passed as input. .TP .B VEOF (004, EOT, Ctrl-D) End-of-file character (EOF). More precisely: this character causes the pending tty buffer to be sent to the waiting user program without waiting for end-of-line. If it is the first character of the line, the .BR read (2) in the user program returns 0, which signifies end-of-file. Recognized when .B ICANON is set, and then not passed as input. .TP .B VEOL (0, NUL) Additional end-of-line character (EOL). Recognized when .B ICANON is set. .TP .B VEOL2 (not in POSIX; 0, NUL) Yet another end-of-line character (EOL2). Recognized when .B ICANON is set. .TP .B VERASE (0177, DEL, rubout, or 010, BS, Ctrl-H, or also #) Erase character (ERASE). This erases the previous not-yet-erased character, but does not erase past EOF or beginning-of-line. Recognized when .B ICANON is set, and then not passed as input. .TP .B VINTR (003, ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt character (INTR). Send a .B SIGINT signal. Recognized when .B ISIG is set, and then not passed as input. .TP .B VKILL (025, NAK, Ctrl-U, or Ctrl-X, or also @) Kill character (KILL). This erases the input since the last EOF or beginning-of-line. Recognized when .B ICANON is set, and then not passed as input. .TP .B VLNEXT (not in POSIX; 026, SYN, Ctrl-V) Literal next (LNEXT). Quotes the next input character, depriving it of a possible special meaning. Recognized when .B IEXTEN is set, and then not passed as input. .TP .B VMIN Minimum number of characters for noncanonical read (MIN). .TP .B VQUIT (034, FS, Ctrl-\e) Quit character (QUIT). Send .B SIGQUIT signal. Recognized when .B ISIG is set, and then not passed as input. .TP .B VREPRINT (not in POSIX; 022, DC2, Ctrl-R) Reprint unread characters (REPRINT). Recognized when .B ICANON and .B IEXTEN are set, and then not passed as input. .TP .B VSTART (021, DC1, Ctrl-Q) Start character (START). Restarts output stopped by the Stop character. Recognized when .B IXON is set, and then not passed as input. .TP .B VSTATUS (not in POSIX; not supported under Linux; status request: 024, DC4, Ctrl-T). Status character (STATUS). Display status information at terminal, including state of foreground process and amount of CPU time it has consumed. Also sends a .B SIGINFO signal (not supported on Linux) to the foreground process group. .TP .B VSTOP (023, DC3, Ctrl-S) Stop character (STOP). Stop output until Start character typed. Recognized when .B IXON is set, and then not passed as input. .TP .B VSUSP (032, SUB, Ctrl-Z) Suspend character (SUSP). Send .B SIGTSTP signal. Recognized when .B ISIG is set, and then not passed as input. .TP .B VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch character (SWTCH). Used in System V to switch shells in .IR "shell layers" , a predecessor to shell job control. .TP .B VTIME Timeout in deciseconds for noncanonical read (TIME). .TP .B VWERASE (not in POSIX; 027, ETB, Ctrl-W) Word erase (WERASE). Recognized when .B ICANON and .B IEXTEN are set, and then not passed as input. .P An individual terminal special character can be disabled by setting the value of the corresponding .I c_cc element to .BR _POSIX_VDISABLE . .P The above symbolic subscript values are all different, except that .BR VTIME , .B VMIN may have the same value as .BR VEOL , .BR VEOF , respectively. In noncanonical mode the special character meaning is replaced by the timeout meaning. For an explanation of .B VMIN and .BR VTIME , see the description of noncanonical mode below. .SS Retrieving and changing terminal settings .BR tcgetattr () gets the parameters associated with the object referred by \fIfd\fP and stores them in the \fItermios\fP structure referenced by \fItermios_p\fP. This function may be invoked from a background process; however, the terminal attributes may be subsequently changed by a foreground process. .P .BR tcsetattr () sets the parameters associated with the terminal (unless support is required from the underlying hardware that is not available) from the \fItermios\fP structure referred to by \fItermios_p\fP. \fIoptional_actions\fP specifies when the changes take effect: .TP .B TCSANOW the change occurs immediately. .TP .B TCSADRAIN the change occurs after all output written to .I fd has been transmitted. This option should be used when changing parameters that affect output. .TP .B TCSAFLUSH the change occurs after all output written to the object referred by .I fd has been transmitted, and all input that has been received but not read will be discarded before the change is made. .SS Canonical and noncanonical mode The setting of the .B ICANON canon flag in .I c_lflag determines whether the terminal is operating in canonical mode .RB ( ICANON set) or noncanonical mode .RB ( ICANON unset). By default, .B ICANON is set. .P In canonical mode: .IP \[bu] 3 Input is made available line by line. An input line is available when one of the line delimiters is typed (NL, EOL, EOL2; or EOF at the start of line). Except in the case of EOF, the line delimiter is included in the buffer returned by .BR read (2). .IP \[bu] Line editing is enabled (ERASE, KILL; and if the .B IEXTEN flag is set: WERASE, REPRINT, LNEXT). A .BR read (2) returns at most one line of input; if the .BR read (2) requested fewer bytes than are available in the current line of input, then only as many bytes as requested are read, and the remaining characters will be available for a future .BR read (2). .IP \[bu] The maximum line length is 4096 chars (including the terminating newline character); lines longer than 4096 chars are truncated. After 4095 characters, input processing (e.g., .B ISIG and .B ECHO* processing) continues, but any input data after 4095 characters up to (but not including) any terminating newline is discarded. This ensures that the terminal can always receive more input until at least one line can be read. .P In noncanonical mode input is available immediately (without the user having to type a line-delimiter character), no input processing is performed, and line editing is disabled. The read buffer will only accept 4095 chars; this provides the necessary space for a newline char if the input mode is switched to canonical. The settings of MIN .RI ( c_cc[VMIN] ) and TIME .RI ( c_cc[VTIME] ) determine the circumstances in which a .BR read (2) completes; there are four distinct cases: .TP MIN == 0, TIME == 0 (polling read) If data is available, .BR read (2) returns immediately, with the lesser of the number of bytes available, or the number of bytes requested. If no data is available, .BR read (2) returns 0. .TP MIN > 0, TIME == 0 (blocking read) .BR read (2) blocks until MIN bytes are available, and returns up to the number of bytes requested. .TP MIN == 0, TIME > 0 (read with timeout) TIME specifies the limit for a timer in tenths of a second. The timer is started when .BR read (2) is called. .BR read (2) returns either when at least one byte of data is available, or when the timer expires. If the timer expires without any input becoming available, .BR read (2) returns 0. If data is already available at the time of the call to .BR read (2), the call behaves as though the data was received immediately after the call. .TP MIN > 0, TIME > 0 (read with interbyte timeout) TIME specifies the limit for a timer in tenths of a second. Once an initial byte of input becomes available, the timer is restarted after each further byte is received. .BR read (2) returns when any of the following conditions is met: .RS .IP \[bu] 3 MIN bytes have been received. .IP \[bu] The interbyte timer expires. .IP \[bu] The number of bytes requested by .BR read (2) has been received. (POSIX does not specify this termination condition, and on some other implementations .\" e.g., Solaris .BR read (2) does not return in this case.) .RE .IP Because the timer is started only after the initial byte becomes available, at least one byte will be read. If data is already available at the time of the call to .BR read (2), the call behaves as though the data was received immediately after the call. .P POSIX .\" POSIX.1-2008 XBD 11.1.7 does not specify whether the setting of the .B O_NONBLOCK file status flag takes precedence over the MIN and TIME settings. If .B O_NONBLOCK is set, a .BR read (2) in noncanonical mode may return immediately, regardless of the setting of MIN or TIME. Furthermore, if no data is available, POSIX permits a .BR read (2) in noncanonical mode to return either 0, or \-1 with .I errno set to .BR EAGAIN . .SS Raw mode .BR cfmakeraw () sets the terminal to something like the "raw" mode of the old Version 7 terminal driver: input is available character by character, echoing is disabled, and all special processing of terminal input and output characters is disabled. The terminal attributes are set as follows: .P .in +4n .EX termios_p\->c_iflag &= \[ti](IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON); termios_p\->c_oflag &= \[ti]OPOST; termios_p\->c_lflag &= \[ti](ECHO | ECHONL | ICANON | ISIG | IEXTEN); termios_p\->c_cflag &= \[ti](CSIZE | PARENB); termios_p\->c_cflag |= CS8; .EE .in .\" .SS Line control .BR tcsendbreak () transmits a continuous stream of zero-valued bits for a specific duration, if the terminal is using asynchronous serial data transmission. If \fIduration\fP is zero, it transmits zero-valued bits for at least 0.25 seconds, and not more than 0.5 seconds. If \fIduration\fP is not zero, it sends zero-valued bits for some implementation-defined length of time. .P If the terminal is not using asynchronous serial data transmission, .BR tcsendbreak () returns without taking any action. .P .BR tcdrain () waits until all output written to the object referred to by .I fd has been transmitted. .P .BR tcflush () discards data written to the object referred to by .I fd but not transmitted, or data received but not read, depending on the value of .IR queue_selector : .TP .B TCIFLUSH flushes data received but not read. .TP .B TCOFLUSH flushes data written but not transmitted. .TP .B TCIOFLUSH flushes both data received but not read, and data written but not transmitted. .P .BR tcflow () suspends transmission or reception of data on the object referred to by .IR fd , depending on the value of .IR action : .TP .B TCOOFF suspends output. .TP .B TCOON restarts suspended output. .TP .B TCIOFF transmits a STOP character, which stops the terminal device from transmitting data to the system. .TP .B TCION transmits a START character, which starts the terminal device transmitting data to the system. .P The default on open of a terminal file is that neither its input nor its output is suspended. .SS Line speed The baud rate functions are provided for getting and setting the values of the input and output baud rates in the \fItermios\fP structure. The new values do not take effect until .BR tcsetattr () is successfully called. .P Setting the speed to \fBB0\fP instructs the modem to "hang up". The actual bit rate corresponding to \fBB38400\fP may be altered with .BR setserial (8). .P The input and output baud rates are stored in the \fItermios\fP structure. .P .BR cfgetospeed () returns the output baud rate stored in the \fItermios\fP structure pointed to by .IR termios_p . .P .BR cfsetospeed () sets the output baud rate stored in the \fItermios\fP structure pointed to by \fItermios_p\fP to \fIspeed\fP, which must be one of these constants: .RS .TP .B B0 .TQ .B B50 .TQ .B B75 .TQ .B B110 .TQ .B B134 .TQ .B B150 .TQ .B B200 .TQ .B B300 .TQ .B B600 .TQ .B B1200 .TQ .B B1800 .TQ .B B2400 .TQ .B B4800 .TQ .B B9600 .TQ .B B19200 .TQ .B B38400 .TQ .B B57600 .TQ .B B115200 .TQ .B B230400 .TQ .B B460800 .TQ .B B500000 .TQ .B B576000 .TQ .B B921600 .TQ .B B1000000 .TQ .B B1152000 .TQ .B B1500000 .TQ .B B2000000 .RE .P These constants are additionally supported on the SPARC architecture: .RS .TP .B B76800 .TQ .B B153600 .TQ .B B307200 .TQ .B B614400 .RE .P These constants are additionally supported on non-SPARC architectures: .RS .TP .B B2500000 .TQ .B B3000000 .TQ .B B3500000 .TQ .B B4000000 .RE .P Due to differences between architectures, portable applications should check if a particular .BI B nnn constant is defined prior to using it. .P The zero baud rate, .BR B0 , is used to terminate the connection. If .B B0 is specified, the modem control lines shall no longer be asserted. Normally, this will disconnect the line. .B CBAUDEX is a mask for the speeds beyond those defined in POSIX.1 (57600 and above). Thus, .BR B57600 " & " CBAUDEX is nonzero. .P Setting the baud rate to a value other than those defined by .BI B nnn constants is possible via the .B TCSETS2 ioctl; see .BR ioctl_tty (2). .P .BR cfgetispeed () returns the input baud rate stored in the .I termios structure. .P .BR cfsetispeed () sets the input baud rate stored in the .I termios structure to .IR speed , which must be specified as one of the .BI B nnn constants listed above for .BR cfsetospeed (). If the input baud rate is set to the literal constant .B 0 (not the symbolic constant .BR B0 ), the input baud rate will be equal to the output baud rate. .P .BR cfsetspeed () is a 4.4BSD extension. It takes the same arguments as .BR cfsetispeed (), and sets both input and output speed. .SH RETURN VALUE .BR cfgetispeed () returns the input baud rate stored in the \fItermios\fP structure. .P .BR cfgetospeed () returns the output baud rate stored in the \fItermios\fP structure. .P All other functions return: .TP .B 0 on success. .TP .B \-1 on failure and set .I errno to indicate the error. .P Note that .BR tcsetattr () returns success if \fIany\fP of the requested changes could be successfully carried out. Therefore, when making multiple changes it may be necessary to follow this call with a further call to .BR tcgetattr () to check that all changes have been performed successfully. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR tcgetattr (), .BR tcsetattr (), .BR tcdrain (), .BR tcflush (), .BR tcflow (), .BR tcsendbreak (), .BR cfmakeraw (), .BR cfgetispeed (), .BR cfgetospeed (), .BR cfsetispeed (), .BR cfsetospeed (), .BR cfsetspeed () T} Thread safety MT-Safe .TE .\" FIXME: The markings are different from that in the glibc manual. .\" markings in glibc manual are more detailed: .\" .\" tcsendbreak: MT-Unsafe race:tcattr(filedes)/bsd .\" tcflow: MT-Unsafe race:tcattr(filedes)/bsd .\" .\" glibc manual says /bsd indicate the preceding marker only applies .\" when the underlying kernel is a BSD kernel. .\" So, it is safety in Linux kernel. .SH STANDARDS .TP .BR tcgetattr () .TQ .BR tcsetattr () .TQ .BR tcsendbreak () .TQ .BR tcdrain () .TQ .BR tcflush () .TQ .BR tcflow () .TQ .BR cfgetispeed () .TQ .BR cfgetospeed () .TQ .BR cfsetispeed () .TQ .BR cfsetospeed () POSIX.1-2008. .TP .BR cfmakeraw () .TQ .BR cfsetspeed () BSD. .SH HISTORY .TP .BR tcgetattr () .TQ .BR tcsetattr () .TQ .BR tcsendbreak () .TQ .BR tcdrain () .TQ .BR tcflush () .TQ .BR tcflow () .TQ .BR cfgetispeed () .TQ .BR cfgetospeed () .TQ .BR cfsetispeed () .TQ .BR cfsetospeed () POSIX.1-2001. .TP .BR cfmakeraw () .TQ .BR cfsetspeed () BSD. .SH NOTES UNIX\ V7 and several later systems have a list of baud rates where after the values .B B0 through .B B9600 one finds the two constants .BR EXTA , .B EXTB ("External A" and "External B"). Many systems extend the list with much higher baud rates. .P The effect of a nonzero \fIduration\fP with .BR tcsendbreak () varies. SunOS specifies a break of .I "duration\ *\ N" seconds, where \fIN\fP is at least 0.25, and not more than 0.5. Linux, AIX, DU, Tru64 send a break of .I duration milliseconds. FreeBSD and NetBSD and HP-UX and MacOS ignore the value of .IR duration . Under Solaris and UnixWare, .BR tcsendbreak () with nonzero .I duration behaves like .BR tcdrain (). .\" libc4 until 4.7.5, glibc for sysv: EINVAL for duration > 0. .\" libc4.7.6, libc5, glibc for unix: duration in ms. .\" glibc for bsd: duration in us .\" glibc for sunos4: ignore duration .SH BUGS .\" kernel 77e5bff1640432f28794a00800955e646dcd7455 .\" glibc 573963e32ffac46d9891970ddebde2ac3212c5c0 On the Alpha architecture before Linux 4.16 (and glibc before glibc 2.28), the .B XTABS value was different from .B TAB3 and it was ignored by the .B N_TTY line discipline code of the terminal driver as a result (because as it wasn't part of the .B TABDLY mask). .SH SEE ALSO .BR reset (1), .BR setterm (1), .BR stty (1), .BR tput (1), .BR tset (1), .BR tty (1), .BR ioctl_console (2), .BR ioctl_tty (2), .BR cc_t (3type), .BR speed_t (3type), .BR tcflag_t (3type), .BR setserial (8)