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TERMIOS(3)		   Linux Programmers Manual		   TERMIOS(3)



NAME
       termios,  tcgetattr,  tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow,
       cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed,  cfsetospeed,	cfset
       speed - get and set terminal attributes, line control, get and set baud
       rate

SYNOPSIS
       #include 
       #include 

       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];   /* control chars */

       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 only exposed 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 IGNPAR is not set, prefix a character with a parity error  or
	      framing  error  with  \377  \0.  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 defined in POSIX.1:

       OPOST  Enable implementation-defined output processing.

       The remaining c_oflag  flag  constants  are  defined  in  POSIX.1-2001,
       unless marked otherwise.

       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  Dont output CR at column 0.

       ONLRET Dont output CR.

       OFILL  Send fill characters for a delay,  rather  than  using  a  timed
	      delay.

       OFDEL  (not  in	POSIX)	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).

       CLOCAL Ignore modem control lines.

       LOBLK  (not in POSIX) Block output from a non-current 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 on Linux.)

       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 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, ASCII control signals other
	      than TAB, NL, START, and STOP are echoed as ^X, where X  is  the
	      character  with ASCII code 0x40 greater than the control signal.
	      For example, character 0x08 (BS) is  echoed  as  ^H.   [requires
	      _BSD_SOURCE or _SVID_SOURCE]

       ECHOPRT
	      (not  in POSIX) If ICANON and IECHO 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
	      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 the
	      SIGINT, SIGQUIT, and SIGSUSP signals.

       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 special control  characters.	 The  symbolic
       indices (initial values) and meaning are:

       VINTR  (003,  ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt charac
	      ter.  Send a SIGINT signal.  Recognized when ISIG  is  set,  and
	      then not passed as input.

       VQUIT  (034,  FS, Ctrl-\) Quit character.  Send SIGQUIT signal.	Recog
	      nized when ISIG is set, and then not passed as input.

       VERASE (0177, DEL, rubout, or 010, BS, Ctrl-H, or also #) Erase charac
	      ter.   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.

       VKILL  (025,  NAK,  Ctrl-U, or Ctrl-X, or also @) Kill character.  This
	      erases the input since the last EOF or beginning-of-line.   Rec
	      ognized when ICANON is set, and then not passed as input.

       VEOF   (004,  EOT, Ctrl-D) End-of-file character.  More precisely: this
	      character causes the pending tty buffer to be sent to the  wait
	      ing  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.

       VMIN   Minimum number of characters for non-canonical read.

       VEOL   (0, NUL)	Additional  end-of-line  character.   Recognized  when
	      ICANON is set.

       VTIME  Timeout in deciseconds for non-canonical read.

       VEOL2  (not  in POSIX; 0, NUL) Yet another end-of-line character.  Rec
	      ognized when ICANON is set.

       VSWTCH (not in POSIX; not supported under Linux; 0, NUL) Switch charac
	      ter.  (Used by shl only.)

       VSTART (021,  DC1, Ctrl-Q) Start character.  Restarts output stopped by
	      the Stop character.  Recognized when IXON is set, and  then  not
	      passed as input.

       VSTOP  (023,  DC3,  Ctrl-S)  Stop  character.   Stop output until Start
	      character typed.	Recognized when IXON  is  set,	and  then  not
	      passed as input.

       VSUSP  (032,  SUB,  Ctrl-Z)  Suspend  character.   Send SIGTSTP signal.
	      Recognized when ISIG is set, and then not passed as input.

       VDSUSP (not in POSIX; not  supported  under  Linux;  031,  EM,  Ctrl-Y)
	      Delayed  suspend character: send SIGTSTP signal when the charac
	      ter 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.

       VLNEXT (not in POSIX; 026, SYN, Ctrl-V) Literal next.  Quotes the  next
	      input  character,  depriving  it	of a possible special meaning.
	      Recognized when IEXTEN is set, and then not passed as input.

       VWERASE
	      (not in POSIX; 027, ETB, Ctrl-W) Word  erase.   Recognized  when
	      ICANON and IEXTEN are set, and then not passed as input.

       VREPRINT
	      (not  in	POSIX;	022,  DC2,  Ctrl-R) Reprint unread characters.
	      Recognized when ICANON and IEXTEN are set, and then  not	passed
	      as input.

       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.

       VSTATUS
	      (not  in	POSIX; not supported under Linux; status request: 024,
	      DC4, Ctrl-T).

       These symbolic subscript values are all different, except  that	VTIME,
       VMIN  may  have	the  same  value as VEOL, VEOF, respectively.  In non-
       canonical mode the special character meaning is replaced by the timeout
       meaning.   For an explanation of VMIN and VTIME, see the description of
       non-canonical 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 pro
       cess.

       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 function 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 non-canonical mode
       The setting of the ICANON canon flag in c_lflag determines whether  the
       terminal  is  operating in canonical mode (ICANON set) or non-canonical
       mode (ICANON unset).  By default, ICANON 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).

       In non-canonical mode input is available immediately (without the  user
       having  to  type  a line-delimiter character), and line editing is dis
       abled.  The settings of MIN (c_cc[VMIN]) and TIME (c_cc[VTIME])	deter
       mine  the  circumstances  in  which a read(2) completes; there are four
       distinct cases:

       * MIN == 0; TIME == 0: If data is available,  read(2)  returns  immedi
	 ately,  with the lesser of the number of bytes available, or the num
	 ber of bytes requested.  If no data is available, read(2) returns  0.

       * MIN  >  0; TIME == 0: read(2) blocks until the lesser of MIN bytes or
	 the number of bytes requested are available, and returns  the	lesser
	 of these two values.

       * MIN == 0; TIME > 0: 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.

       * MIN  > 0; TIME > 0: 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
	 either when the lesser of the number of bytes requested or  MIN  byte
	 have  been read, or when the inter-byte timeout expires.  Because the
	 timer is only started after the initial byte  becomes	available,  at
	 least one byte will be read.

   Raw mode
       cfmakeraw()  sets  the terminal to something like the "raw" mode of the
       old Version 7 terminal driver: input is available character by  charac
       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.

   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 struc
       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 non-zero.

       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.

       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.

CONFORMING TO
       tcgetattr(),   tcsetattr(),   tcsendbreak(),   tcdrain(),    tcflush(),
       tcflow(),   cfgetispeed(),   cfgetospeed(),  cfsetispeed(),  and  cfse
       tospeed() are specified in POSIX.1-2001.

       cfmakeraw() and cfsetspeed() are non-standard,  but  available  on  the
       BSDs.

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 non-zero 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  non-zero
       duration behaves like tcdrain().

SEE ALSO
       stty(1), console_ioctl(4), tty_ioctl(4), setserial(8)

COLOPHON
       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux				  2007-11-26			    TERMIOS(3)




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