Examining tty and cblock structures

The tty command prints the entries in the tty table for
console multiscreens, parallel ports, serial ports, and pseudo-ttys. If you specify the -f option, the information displayed includes:

• the addresses of the control blocks and the first and last
  
  
  
  character block cblock structures in the character lists (clist structures) used to implement the raw input, canonical input, and output data queues

• control character settings

• line settings such as speed, parity, and character size

The cblock command allows you to examine the contents of

the character blocks for a clist given its table entry displayed by the tty command. This may be useful if you wish to examine the a serial line which you think may be generating spurious characters. Figure D-4 illustrates how a character list is built from a clist header and a chain of cblock elements. The clist header contains pointers to the first and last cblock only. The total count of characters in the c_data buffers is stored in the c_cc member of the clist.

Figure D-4 A character list formed from a chain of character blocks