Terminal device control

These system calls deal with a general terminal interface for the control of asynchronous communications ports.

Terminal device control functions

tcgetattr tcsetattr	get and set terminal attributes
tcdrain tcflush	line control functions
tcflow tcsendbreak	line control functions
cfgetispeed cfgetospeed	get baud rate functions
cfsetispeed cfsetospeed	set baud rate functions
tcgetsid	get terminal session ID
tcgetpgrp	get terminal foreground process group ID
tcsetpgrp	set terminal foreground process group ID