TCSENDBREAK(3)         FreeBSD 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
             terminal to stop transmitting data to the system.  (See the
             description of IXOFF in the `Input Modes' section of termios(4)).

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

     The tcflush() function discards any data written to the terminal
     referenced 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 default value for
     kern.tty_drainwait is 300 seconds.

FreeBSD 13.1-RELEASE-p6        January 11, 2017        FreeBSD 13.1-RELEASE-p6