tcflush - discard non-transmitted data

Syntax	#include <termios.h> int tcflush(int fildes, int queue_selector);
Description	fildes is a file descriptor associated with a terminal. Upon successful completion, tcflush() discards data that was written to the object referred to by fildes but not transmitted, or data that was received but not read, depending on the value of queue_selector: If queue_selector is TCIFLUSH, data that was received but not read is flushed; if queue_selector is TCOFLUSH, data that was written but not transmitted is flushed, and if queue_selector is TCIOFLUSH, both the data that was received but not read and the data that was written but not transmitted are flushed. Attempts to use tcflush() from a process which is a member of a background process group on a fildes associated with its controlling terminal, will cause the process group to be sent a SIGTTOU signal. If the calling process is blocking or ignoring SIGTTOU signals, the process is allowed to perform the operation, and no SIGTTOU signal is sent. Extension All values are supported for connections with a remote processor. (End)
Return val.	0 -1	if successful. if an error occurs. errno is set to indicate the error.
Errors	tcflush() will fail if:
	EBADF	fildes is not a valid file descriptor.
	EINVAL	queue_selector is not a supported value.
	Extension
	EINVAL	An attempt was made to access a BS2000 file. (End)
	EIO	The process group of the writing process is orphaned, and the writing process is not ignoring or blocking SIGTTOU.
	ENOTTY	The file associated with fildes is not a terminal.
Notes	tcflush() has no effect on block-mode terminals.
See also	tcdrain(), termios.h, unistd.h, section “General terminal interface”.