What is a pseudo tty?
In Unix, a pseudo terminal is a pseudo-device pair that provides a text terminal interface without associated virtual console, computer terminal or serial port hardware. Instead, a process replaces the role of the underlying hardware for the pseudo terminal session.For each pseudo terminal, the operating system kernel provides two character devices: a master device and a slave device.The master and slave devices, in their most common deployment, form an association between a Unix shell and a terminal emulation program or some sort of network server.The slave device file, which generally has a nomenclature of /dev/ttyp*, has the appearance and supported system calls of any text terminal. Thus it has the understanding of a login session and session leader process (which is typically the shell program).The master device file, which generally has a nomenclature of /dev/ptyp*, is the endpoint for communication with the terminal emulator. It receives the control requests and information from the other party over this interface and responds accordingly.