Flush buffers
Synopsis:
#include <sys/ioctl.h>
#define TIOCFLUSH       _IOW('t', 16, int)
Arguments to ioctl():
  | Argument | Value | 
  | fd | A file descriptor that you obtained by opening the device | 
  | request | TIOCFLUSH | 
  | Additional argument | A pointer to an integer | 
Description:
This command flushes the input and/or output stream associated with the file descriptor.
It's also implemented as the
DCMD_CHR_TCFLUSH
devctl() command.
Note: 
This command is for internal use, and you shouldn't use it directly.
Instead use the
tcflush()
cover function.
 
Input:
The queue selector; one of:
- FREAD — discard all data that's received,
  but not yet read, on the device associated with fildes.
  
- FWRITE — 
  discard all data that's written, but not yet transmitted, on
  the device associated with fildes.
  
- 0 —
  discard all data that's written, but not yet transmitted, 
  as well as all data that's received, but not yet read, on
  the device associated with fildes.