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TCSENDBREAK(3)		    Library Functions Manual		TCSENDBREAK(3)

NAME
       tcsendbreak, tcdrain, tcflush, tcflow --	line control functions

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<termios.h>

       int
       tcdrain(int fd);

       int
       tcflow(int fd, int action);

       int
       tcflush(int fd, int action);

       int
       tcsendbreak(int fd, int len);

DESCRIPTION
       The  tcdrain()  function	waits until all	output written to the terminal
       referenced by fd	has been transmitted to	the terminal.

       The tcflow() function suspends transmission of data to or the reception
       of data from the	terminal referenced by fd depending on	the  value  of
       action.	The value of action must be one	of the following:

       TCOOFF  Suspend output.

       TCOON   Restart suspended output.

       TCIOFF  Transmit	 a STOP	character, which is intended to	cause the ter-
	       minal to	stop transmitting data to the system.	(See  the  de-
	       scription of IXOFF in the `Input	Modes' section of termios(4)).

       TCION   Transmit	a START	character, which is intended to	cause the ter-
	       minal  to  start	transmitting data to the system.  (See the de-
	       scription of IXOFF in the `Input	Modes' section of termios(4)).

       The tcflush() function discards any data	written	to the terminal	refer-
       enced by	fd which has not been transmitted to the terminal, or any data
       received	from the terminal but not yet read, depending on the value  of
       action.	The value of action must be one	of the following:

       TCIFLUSH	  Flush	data received but not read.

       TCOFLUSH	  Flush	data written but not transmitted.

       TCIOFLUSH  Flush	 both  data received but not read and data written but
		  not transmitted.

       The tcsendbreak() function transmits a continuous stream	of zero-valued
       bits for	four-tenths of a second	to the terminal	referenced by fd.  The
       len argument is ignored in this implementation.

RETURN VALUES
       Upon successful completion, all of these	functions return  a  value  of
       zero.

ERRORS
       If  any error occurs, a value of	-1 is returned and the global variable
       errno is	set to indicate	the error, as follows:

       [EBADF]		  The fd argument is not a valid file descriptor.

       [EINVAL]		  The action argument is not a proper value.

       [ENOTTY]		  The file associated with fd is not a terminal.

       [EINTR]		  A signal interrupted the tcdrain() function.

       [EWOULDBLOCK]	  The configured timeout expired before	the  tcdrain()
			  function could write all buffered output.

SEE ALSO
       tcsetattr(3), termios(4), tty(4), comcontrol(8)

STANDARDS
       The  tcsendbreak(), tcflush() and tcflow() functions are	expected to be
       compliant with the IEEE Std 1003.1-1988 ("POSIX.1") specification.

       The tcdrain() function is  expected  to	be  compliant  with  IEEE  Std
       1003.1-1988  ("POSIX.1")	 when the drain	wait value is set to zero with
       comcontrol(8), or  with	ioctl(2)  TIOCSDRAINWAIT,  or  with  sysctl(8)
       kern.tty_drainwait.    A	 non-zero  drain  wait	value  can  result  in
       tcdrain() returning EWOULDBLOCK without writing all  output.   The  de-
       fault value for kern.tty_drainwait is 300 seconds.

FreeBSD	14.3		       January 11, 2017			TCSENDBREAK(3)

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<https://man.freebsd.org/cgi/man.cgi?query=tcdrain&sektion=3&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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