# termios

## 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
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#include <termios.h>**
           **#include <unistd.h>**
    
           **int tcgetattr(int** _fd_**, struct termios ***_termios_p_**);**
           **int tcsetattr(int** _fd_**, int** _optional_actions_**,**
                         **const struct termios ***_termios_p_**);**
    
           **int tcsendbreak(int** _fd_**, int** _duration_**);**
           **int tcdrain(int** _fd_**);**
           **int tcflush(int** _fd_**, int** _queue_selector_**);**
           **int tcflow(int** _fd_**, int** _action_**);**
    
           **void cfmakeraw(struct termios ***_termios_p_**);**
    
           **speed_t cfgetispeed(const struct termios ***_termios_p_**);**
           **speed_t cfgetospeed(const struct termios ***_termios_p_**);**
    
           **int cfsetispeed(struct termios ***_termios_p_**, speed_t** _speed_**);**
           **int cfsetospeed(struct termios ***_termios_p_**, speed_t** _speed_**);**
           **int cfsetspeed(struct termios ***_termios_p_**, speed_t** _speed_**);**
    
       Feature Test Macro Requirements for glibc (see
       feature_test_macros(7)):
    
           **cfsetspeed**(), **cfmakeraw**():
               Since glibc 2.19:
                   _DEFAULT_SOURCE
               glibc 2.19 and earlier:
                   _BSD_SOURCE
    


## DESCRIPTION



           The termios functions describe a general terminal interface that
           is provided to control asynchronous communications ports.
    
       **The termios structure**
           Many of the functions described here have a _termios_p_ argument
           that is a pointer to a _termios_ structure.  This structure contains
           at least the following members:
    
               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 */
    
           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
           feature_test_macros(7)) is defined, as noted in brackets ("[]").
    
           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.
    
           _c_iflag_ flag constants:
    
           **IGNBRK** Ignore BREAK condition on input.
    
           **BRKINT** If **IGNBRK** is set, a BREAK is ignored.  If it is not set but
                  **BRKINT** 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 **SIGINT** to be sent to this foreground process group.
                  When neither **IGNBRK** nor **BRKINT** are set, a BREAK reads as a
                  null byte (**'\0'**), except when **PARMRK** is set, in which case
                  it reads as the sequence \377 \0 \0.
    
           **IGNPAR** Ignore framing errors and parity errors.
    
           **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 **INPCK** is set and **IGNPAR** is not set.
                  The way erroneous bytes are marked is with two preceding
                  bytes, \377 and \0.  Thus, the program actually reads three
                  bytes for one erroneous byte received from the terminal.
                  If a valid byte has the value \377, and **ISTRIP**(see below)
                  is not set, the program might confuse it with the prefix
                  that marks a parity error.  Therefore, a valid byte \377 is
                  passed to the program as two bytes, \377 \377, in this
                  case.
    
                  If neither **IGNPAR** nor **PARMRK** is set, read a character with
                  a parity error or framing error as \0.
    
           **INPCK** Enable input parity checking.
    
           **ISTRIP** Strip off eighth bit.
    
           **INLCR** Translate NL to CR on input.
    
           **IGNCR** Ignore carriage return on input.
    
           **ICRNL** Translate carriage return to newline on input (unless **IGNCR**
                  is set).
    
           **IUCLC**(not in POSIX) Map uppercase characters to lowercase on
                  input.
    
           **IXON** Enable XON/XOFF flow control on output.
    
           **IXANY**(XSI) Typing any character will restart stopped output.
                  (The default is to allow just the START character to
                  restart output.)
    
           **IXOFF** Enable XON/XOFF flow control on input.
    
           **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.
    
           **IUTF8**(since Linux 2.6.4)
                  (not in POSIX) Input is UTF8; this allows character-erase
                  to be correctly performed in cooked mode.
    
           _c_oflag_ flag constants:
    
           **OPOST** Enable implementation-defined output processing.
    
           **OLCUC**(not in POSIX) Map lowercase characters to uppercase on
                  output.
    
           **ONLCR**(XSI) Map NL to CR-NL on output.
    
           **OCRNL** Map CR to NL on output.
    
           **ONOCR** Don't output CR at column 0.
    
           **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.
    
           **OFILL** Send fill characters for a delay, rather than using a timed
                  delay.
    
           **OFDEL** Fill character is ASCII DEL (0177).  If unset, fill
                  character is ASCII NUL ('\0').  (Not implemented on Linux.)
    
           **NLDLY** Newline delay mask.  Values are **NL0** and **NL1**.  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE** or **_XOPEN_SOURCE**]
    
           **CRDLY** Carriage return delay mask.  Values are **CR0** , **CR1** , **CR2** , or
                  **CR3**.  [requires **_BSD_SOURCE** or **_SVID_SOURCE** or
                  **_XOPEN_SOURCE**]
    
           **TABDLY** Horizontal tab delay mask.  Values are **TAB0** , **TAB1** , **TAB2** ,
                  **TAB3**(or **XTABS** , but see the **BUGS** section).  A value of
                  TAB3, that is, XTABS, expands tabs to spaces (with tab
                  stops every eight columns).  [requires **_BSD_SOURCE** or
                  **_SVID_SOURCE** or **_XOPEN_SOURCE**]
    
           **BSDLY** Backspace delay mask.  Values are **BS0** or **BS1**.  (Has never
                  been implemented.)  [requires **_BSD_SOURCE** or **_SVID_SOURCE**
                  or **_XOPEN_SOURCE**]
    
           **VTDLY** Vertical tab delay mask.  Values are **VT0** or **VT1**.
    
           **FFDLY** Form feed delay mask.  Values are **FF0** or **FF1**.  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE** or **_XOPEN_SOURCE**]
    
           _c_cflag_ flag constants:
    
           **CBAUD**(not in POSIX) Baud speed mask (4+1 bits).  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **CBAUDEX**
                  (not in POSIX) Extra baud speed mask (1 bit), included in
                  **CBAUD**.  [requires **_BSD_SOURCE** or **_SVID_SOURCE**]
    
                  (POSIX says that the baud speed is stored in the _termios_
                  structure without specifying where precisely, and provides
                  **cfgetispeed**() and **cfsetispeed**() for getting at it.  Some
                  systems use bits selected by **CBAUD** in _c_cflag_ , other
                  systems use separate fields, for example, _sg_ispeed_ and
                  _sg_ospeed_.)
    
           **CSIZE** Character size mask.  Values are **CS5** , **CS6** , **CS7** , or **CS8**.
    
           **CSTOPB** Set two stop bits, rather than one.
    
           **CREAD** Enable receiver.
    
           **PARENB** Enable parity generation on output and parity checking for
                  input.
    
           **PARODD** If set, then parity for input and output is odd; otherwise
                  even parity is used.
    
           **HUPCL** Lower modem control lines after last process closes the
                  device (hang up).
    
           **CLOCAL** Ignore modem control lines.
    
           **LOBLK**(not in POSIX) Block output from a noncurrent shell layer.
                  For use by **shl**(shell layers).  (Not implemented on Linux.)
    
           **CIBAUD**(not in POSIX) Mask for input speeds.  The values for the
                  **CIBAUD** bits are the same as the values for the **CBAUD** bits,
                  shifted left **IBSHIFT** bits.  [requires **_BSD_SOURCE** or
                  **_SVID_SOURCE**] (Not implemented in glibc, supported on Linux
                  via **TCGET** * and **TCSET** * ioctls; see ioctl_tty(2))
    
           **CMSPAR**(not in POSIX) Use "stick" (mark/space) parity (supported
                  on certain serial devices): if **PARODD** is set, the parity
                  bit is always 1; if **PARODD** is not set, then the parity bit
                  is always 0.  [requires **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **CRTSCTS**
                  (not in POSIX) Enable RTS/CTS (hardware) flow control.
                  [requires **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           _c_lflag_ flag constants:
    
           **ISIG** When any of the characters INTR, QUIT, SUSP, or DSUSP are
                  received, generate the corresponding signal.
    
           **ICANON** Enable canonical mode (described below).
    
           **XCASE**(not in POSIX; not supported under Linux) If **ICANON** is also
                  set, terminal is uppercase only.  Input is converted to
                  lowercase, except for characters preceded by \.  On output,
                  uppercase characters are preceded by \ and lowercase
                  characters are converted to uppercase.  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE** or **_XOPEN_SOURCE**]
    
           **ECHO** Echo input characters.
    
           **ECHOE** If **ICANON** is also set, the ERASE character erases the
                  preceding input character, and WERASE erases the preceding
                  word.
    
           **ECHOK** If **ICANON** is also set, the KILL character erases the
                  current line.
    
           **ECHONL** If **ICANON** is also set, echo the NL character even if ECHO
                  is not set.
    
           **ECHOCTL**
                  (not in POSIX) If **ECHO** is also set, terminal special
                  characters other than TAB, NL, START, and STOP are echoed
                  as **^X** , where X is the character with ASCII code 0x40
                  greater than the special character.  For example, character
                  0x08 (BS) is echoed as **^H**.  [requires **_BSD_SOURCE** or
                  **_SVID_SOURCE**]
    
           **ECHOPRT**
                  (not in POSIX) If **ICANON** and **ECHO** are also set, characters
                  are printed as they are being erased.  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **ECHOKE**(not in POSIX) If **ICANON** is also set, KILL is echoed by
                  erasing each character on the line, as specified by **ECHOE**
                  and **ECHOPRT**.  [requires **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **DEFECHO**
                  (not in POSIX) Echo only when a process is reading.  (Not
                  implemented on Linux.)
    
           **FLUSHO**(not in POSIX; not supported under Linux) Output is being
                  flushed.  This flag is toggled by typing the DISCARD
                  character.  [requires **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **NOFLSH** Disable flushing the input and output queues when
                  generating signals for the INT, QUIT, and SUSP characters.
    
           **TOSTOP** Send the **SIGTTOU** signal to the process group of a
                  background process which tries to write to its controlling
                  terminal.
    
           **PENDIN**(not in POSIX; not supported under Linux) All characters in
                  the input queue are reprinted when the next character is
                  read.  (bash(1) handles typeahead this way.)  [requires
                  **_BSD_SOURCE** or **_SVID_SOURCE**]
    
           **IEXTEN** Enable implementation-defined input processing.  This flag,
                  as well as **ICANON** must be enabled for the special
                  characters EOL2, LNEXT, REPRINT, WERASE to be interpreted,
                  and for the **IUCLC** flag to be effective.
    
           The _c_cc_ array defines the terminal special characters.  The
           symbolic indices (initial values) and meaning are:
    
           **VDISCARD**
                  (not in POSIX; not supported under Linux; 017, SI, Ctrl-O)
                  Toggle: start/stop discarding pending output.  Recognized
                  when **IEXTEN** is set, and then not passed as input.
    
           **VDSUSP**(not in POSIX; not supported under Linux; 031, EM, Ctrl-Y)
                  Delayed suspend character (DSUSP): send **SIGTSTP** signal when
                  the character is read by the user program.  Recognized when
                  **IEXTEN** and **ISIG** are set, and the system supports job
                  control, and then not passed as input.
    
           **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
                  read(2) in the user program returns 0, which signifies end-
                  of-file.  Recognized when **ICANON** is set, and then not
                  passed as input.
    
           **VEOL**(0, NUL) Additional end-of-line character (EOL).
                  Recognized when **ICANON** is set.
    
           **VEOL2**(not in POSIX; 0, NUL) Yet another end-of-line character
                  (EOL2).  Recognized when **ICANON** is set.
    
           **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 **ICANON** is set, and then not passed
                  as input.
    
           **VINTR**(003, ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt
                  character (INTR).  Send a **SIGINT** signal.  Recognized when
                  **ISIG** is set, and then not passed as input.
    
           **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 **ICANON** is set, and then
                  not passed as input.
    
           **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 **IEXTEN** is set, and then
                  not passed as input.
    
           **VMIN** Minimum number of characters for noncanonical read (MIN).
    
           **VQUIT**(034, FS, Ctrl-\) Quit character (QUIT).  Send **SIGQUIT**
                  signal.  Recognized when **ISIG** is set, and then not passed
                  as input.
    
           **VREPRINT**
                  (not in POSIX; 022, DC2, Ctrl-R) Reprint unread characters
                  (REPRINT).  Recognized when **ICANON** and **IEXTEN** are set, and
                  then not passed as input.
    
           **VSTART**(021, DC1, Ctrl-Q) Start character (START).  Restarts
                  output stopped by the Stop character.  Recognized when **IXON**
                  is set, and then not passed as input.
    
           **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 **SIGINFO** signal (not supported on Linux) to the
                  foreground process group.
    
           **VSTOP**(023, DC3, Ctrl-S) Stop character (STOP).  Stop output
                  until Start character typed.  Recognized when **IXON** is set,
                  and then not passed as input.
    
           **VSUSP**(032, SUB, Ctrl-Z) Suspend character (SUSP).  Send **SIGTSTP**
                  signal.  Recognized when **ISIG** is set, and then not passed
                  as input.
    
           **VSWTCH**(not in POSIX; not supported under Linux; 0, NUL) Switch
                  character (SWTCH).  Used in System V to switch shells in
                  _shell layers_ , a predecessor to shell job control.
    
           **VTIME** Timeout in deciseconds for noncanonical read (TIME).
    
           **VWERASE**
                  (not in POSIX; 027, ETB, Ctrl-W) Word erase (WERASE).
                  Recognized when **ICANON** and **IEXTEN** are set, and then not
                  passed as input.
    
           An individual terminal special character can be disabled by
           setting the value of the corresponding _c_cc_ element to
           **_POSIX_VDISABLE**.
    
           The above symbolic subscript values are all different, except that
           **VTIME** , **VMIN** may have the same value as **VEOL** , **VEOF** , respectively.
           In noncanonical mode the special character meaning is replaced by
           the timeout meaning.  For an explanation of **VMIN** and **VTIME** , see
           the description of noncanonical mode below.
    
       **Retrieving and changing terminal settings**
           **tcgetattr**() gets the parameters associated with the object
           referred by _fd_ and stores them in the _termios_ structure referenced
           by _termios_p_.  This function may be invoked from a background
           process; however, the terminal attributes may be subsequently
           changed by a foreground process.
    
           **tcsetattr**() sets the parameters associated with the terminal
           (unless support is required from the underlying hardware that is
           not available) from the _termios_ structure referred to by
           _termios_p_.  _optional_actions_ specifies when the changes take
           effect:
    
           **TCSANOW**
                  the change occurs immediately.
    
           **TCSADRAIN**
                  the change occurs after all output written to _fd_ has been
                  transmitted.  This option should be used when changing
                  parameters that affect output.
    
           **TCSAFLUSH**
                  the change occurs after all output written to the object
                  referred by _fd_ has been transmitted, and all input that has
                  been received but not read will be discarded before the
                  change is made.
    
       **Canonical and noncanonical mode**
           The setting of the **ICANON** canon flag in _c_lflag_ determines whether
           the terminal is operating in canonical mode (**ICANON** set) or
           noncanonical mode (**ICANON** unset).  By default, **ICANON** is set.
    
           In canonical mode:
    
           •  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
              read(2).
    
           •  Line editing is enabled (ERASE, KILL; and if the **IEXTEN** flag is
              set: WERASE, REPRINT, LNEXT).  A read(2) returns at most one
              line of input; if the 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 read(2).
    
           •  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.,
              **ISIG** and **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.
    
           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 (_c_cc[VMIN]_) and TIME
           (_c_cc[VTIME]_) determine the circumstances in which a read(2)
           completes; there are four distinct cases:
    
           MIN == 0, TIME == 0 (polling read)
                  If data is available, read(2) returns immediately, with the
                  lesser of the number of bytes available, or the number of
                  bytes requested.  If no data is available, read(2) returns
                  0.
    
           MIN > 0, TIME == 0 (blocking read)
                  read(2) blocks until MIN bytes are available, and returns
                  up to the number of bytes requested.
    
           MIN == 0, TIME > 0 (read with timeout)
                  TIME specifies the limit for a timer in tenths of a second.
                  The timer is started when read(2) is called.  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, read(2) returns 0.  If data
                  is already available at the time of the call to read(2),
                  the call behaves as though the data was received
                  immediately after the call.
    
           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.  read(2)
                  returns when any of the following conditions is met:
    
                  •  MIN bytes have been received.
    
                  •  The interbyte timer expires.
    
                  •  The number of bytes requested by read(2) has been
                     received.  (POSIX does not specify this termination
                     condition, and on some other implementations read(2)
                     does not return in this case.)
    
                  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 read(2),
                  the call behaves as though the data was received
                  immediately after the call.
    
           POSIX does not specify whether the setting of the **O_NONBLOCK** file
           status flag takes precedence over the MIN and TIME settings.  If
           **O_NONBLOCK** is set, a 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 read(2) in
           noncanonical mode to return either 0, or -1 with _errno_ set to
           **EAGAIN**.
    
       **Raw mode**
           **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:
    
               termios_p->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
                               | INLCR | IGNCR | ICRNL | IXON);
               termios_p->c_oflag &= ~OPOST;
               termios_p->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
               termios_p->c_cflag &= ~(CSIZE | PARENB);
               termios_p->c_cflag |= CS8;
    
       **Line control**
           **tcsendbreak**() transmits a continuous stream of zero-valued bits
           for a specific duration, if the terminal is using asynchronous
           serial data transmission.  If _duration_ is zero, it transmits zero-
           valued bits for at least 0.25 seconds, and not more than 0.5
           seconds.  If _duration_ is not zero, it sends zero-valued bits for
           some implementation-defined length of time.
    
           If the terminal is not using asynchronous serial data
           transmission, **tcsendbreak**() returns without taking any action.
    
           **tcdrain**() waits until all output written to the object referred to
           by _fd_ has been transmitted.
    
           **tcflush**() discards data written to the object referred to by _fd_
           but not transmitted, or data received but not read, depending on
           the value of _queue_selector_ :
    
           **TCIFLUSH**
                  flushes data received but not read.
    
           **TCOFLUSH**
                  flushes data written but not transmitted.
    
           **TCIOFLUSH**
                  flushes both data received but not read, and data written
                  but not transmitted.
    
           **tcflow**() suspends transmission or reception of data on the object
           referred to by _fd_ , depending on the value of _action_ :
    
           **TCOOFF** suspends output.
    
           **TCOON** restarts suspended output.
    
           **TCIOFF** transmits a STOP character, which stops the terminal device
                  from transmitting data to the system.
    
           **TCION** transmits a START character, which starts the terminal
                  device transmitting data to the system.
    
           The default on open of a terminal file is that neither its input
           nor its output is suspended.
    
       **Line speed**
           The baud rate functions are provided for getting and setting the
           values of the input and output baud rates in the _termios_
           structure.  The new values do not take effect until **tcsetattr**() is
           successfully called.
    
           Setting the speed to **B0** instructs the modem to "hang up".  The
           actual bit rate corresponding to **B38400** may be altered with
           **setserial**(8).
    
           The input and output baud rates are stored in the _termios_
           structure.
    
           **cfgetospeed**() returns the output baud rate stored in the _termios_
           structure pointed to by _termios_p_.
    
           **cfsetospeed**() sets the output baud rate stored in the _termios_
           structure pointed to by _termios_p_ to _speed_ , which must be one of
           these constants:
    
                  **B0**
                  **B50**
                  **B75**
                  **B110**
                  **B134**
                  **B150**
                  **B200**
                  **B300**
                  **B600**
                  **B1200**
                  **B1800**
                  **B2400**
                  **B4800**
                  **B9600**
                  **B19200**
                  **B38400**
                  **B57600**
                  **B115200**
                  **B230400**
                  **B460800**
                  **B500000**
                  **B576000**
                  **B921600**
                  **B1000000**
                  **B1152000**
                  **B1500000**
                  **B2000000**
    
           These constants are additionally supported on the SPARC
           architecture:
    
                  **B76800**
                  **B153600**
                  **B307200**
                  **B614400**
    
           These constants are additionally supported on non-SPARC
           architectures:
    
                  **B2500000**
                  **B3000000**
                  **B3500000**
                  **B4000000**
    
           Due to differences between architectures, portable applications
           should check if a particular **B** _nnn_ constant is defined prior to
           using it.
    
           The zero baud rate, **B0** , is used to terminate the connection.  If
           **B0** is specified, the modem control lines shall no longer be
           asserted.  Normally, this will disconnect the line.  **CBAUDEX** is a
           mask for the speeds beyond those defined in POSIX.1 (57600 and
           above).  Thus, **B57600** & **CBAUDEX** is nonzero.
    
           Setting the baud rate to a value other than those defined by **B** _nnn_
           constants is possible via the **TCSETS2** ioctl; see ioctl_tty(2).
    
           **cfgetispeed**() returns the input baud rate stored in the _termios_
           structure.
    
           **cfsetispeed**() sets the input baud rate stored in the _termios_
           structure to _speed_ , which must be specified as one of the **B** _nnn_
           constants listed above for **cfsetospeed**().  If the input baud rate
           is set to the literal constant **0**(not the symbolic constant **B0**),
           the input baud rate will be equal to the output baud rate.
    
           **cfsetspeed**() is a 4.4BSD extension.  It takes the same arguments
           as **cfsetispeed**(), and sets both input and output speed.
    


## RETURN VALUE



           **cfgetispeed**() returns the input baud rate stored in the _termios_
           structure.
    
           **cfgetospeed**() returns the output baud rate stored in the _termios_
           structure.
    
           All other functions return:
    
           **0** on success.
    
           **-1** on failure and set _errno_ to indicate the error.
    
           Note that **tcsetattr**() returns success if _any_ 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 **tcgetattr**() to check that all changes have been
           performed successfully.
    


## ATTRIBUTES



           For an explanation of the terms used in this section, see
           attributes(7).
           ┌──────────────────────────────────────┬───────────────┬─────────┐
           │ **Interface** │ **Attribute** │ **Value** │
           ├──────────────────────────────────────┼───────────────┼─────────┤
           │ **tcgetattr**(), **tcsetattr**(), **tcdrain**(), │ Thread safety │ MT-Safe │
           │ **tcflush**(), **tcflow**(), **tcsendbreak**(),  │               │         │
           │ **cfmakeraw**(), **cfgetispeed**(),          │               │         │
           │ **cfgetospeed**(), **cfsetispeed**(),        │               │         │
           │ **cfsetospeed**(), **cfsetspeed**()          │               │         │
           └──────────────────────────────────────┴───────────────┴─────────┘
    


## STANDARDS



           **tcgetattr**()
           **tcsetattr**()
           **tcsendbreak**()
           **tcdrain**()
           **tcflush**()
           **tcflow**()
           **cfgetispeed**()
           **cfgetospeed**()
           **cfsetispeed**()
           **cfsetospeed**()
                  POSIX.1-2008.
    
           **cfmakeraw**()
           **cfsetspeed**()
                  BSD.
    


## NOTES



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


## BUGS



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


* * *