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What is the exact difference between a ‘terminal’, a ‘shell’, a ‘tty’ and a ‘console’?
This question follows directly from another question of mine in this great forum. What exactly is the concept of a Pseudo Terminal in Linux speak? Can you please explain with an example. Is it a different concept from Terminal emulators?
A terminal is a piece of hardware with a screen and a keyboard, usually connected using a serial line to a computer. In case of a Unix computer it is served by the getty process, which provides a shell to the user.
A pseudo terminal is a terminal session (also providing a shell to the user), which uses a virtual connection via TCP instead of a serial line. Such a pseudo terminal is usually served by the sshd, less securely also by the telnetd.
A terminal emulator is the client program, the users uses to open such a pseudo terminal.
In an overly simplified format:
Pseudo terminal = a device file on your unix system when not being used; a process on your unix system attached to the aforementioned device file for input/output.
Terminal emulator = an application running on your local desktop, making a telnet or ssh connection to a remote server.
