cfgetospeed

       rate

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(): _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
              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  con-
              fuse 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.
              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).   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  struc-
              ture   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 sepa-
              rate 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).
              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 char-
              acters  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 imple-
              mented on Linux.)

       FLUSHO (not  in  POSIX;  not  supported  under  Linux)  Output is being
              _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)  Tog-
              gle: start/stop discarding pending output.  Recognized when IEX-
              TEN 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 charac-
              ter (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  charac-
              ter (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).

       VSTATUS
              (not in POSIX; not supported under Linux; status  request:  024,
              DC4, Ctrl-T).  Status character (STATUS).  Display status infor-
              mation 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  sig-
              nal.  Recognized when ISIG is set, and then not passed as input.

       VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch charac-
              ter (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).  Recog-
              nized 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 trans-
              mitted.  This option should be  used  when  changing  parameters
              that affect output.


       * 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).

       In  noncanonical  mode input is available immediately (without the user
       having to type a line-delimiter character), no input processing is per-
       formed, and line editing is disabled.  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 avail-
              able, 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

       ter, 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 that 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.
       ture 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

       The  zero baud rate, B0, is used to terminate the connection.  If B0 is
       specified, the modem control lines shall no longer be  asserted.   Nor-
       mally, 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.

       cfgetispeed()  returns the input baud rate stored in the termios struc-
       ture.

       cfsetispeed() sets the input baud rate stored in the termios  structure
       to  speed,  which must be specified as one of the Bnnn constants listed
       above for cfsetospeed().  If the input baud rate is set  to  zero,  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  struc-
       ture.

       cfgetospeed() returns the output baud rate stored in the termios struc-
       ture.

       All other functions return:

       0      on success.

       -1     on failure and set errno to indicate the error.
       +-------------------------------------+---------------+---------+
       |tcgetattr(), tcsetattr(), tcdrain(), | Thread safety | MT-Safe |
       |tcflush(), tcflow(), tcsendbreak(),  |               |         |
       |cfmakeraw(), cfgetispeed(),          |               |         |
       |cfgetospeed(), cfsetispeed(),        |               |         |
       |cfsetospeed(), cfsetspeed()          |               |         |
       +-------------------------------------+---------------+---------+
CONFORMING TO
       tcgetattr(),   tcsetattr(),   tcsendbreak(),   tcdrain(),    tcflush(),
       tcflow(),   cfgetispeed(),   cfgetospeed(),  cfsetispeed(),  and  cfse-
       tospeed() are specified in POSIX.1-2001.

       cfmakeraw() and cfsetspeed() are nonstandard, but available on the  BS-
       Ds.

NOTES
       UNIX V7 and several later systems have a list of baud rates where after
       the fourteen values B0, ..., 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().

SEE ALSO
       reset(1),  setterm(1),  stty(1),  tput(1),  tset(1),  console_ioctl(4),
       tty_ioctl(4), setserial(8)

COLOPHON
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       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       http://www.kernel.org/doc/man-pages/.

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