TCSENDBREAK(3)

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

LIBRARY
libc

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 p1003.1-88 specification.

The tcdrain() function is expected to be compliant with p1003.1-88 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.