Shell and Bash Terminals

[Felipalds]

Hello everyone. I would like to bring the discussion about shell and terminals that we had Tuesday and for me it is not very clear:

• what is the difference between I use the Linux main terminal or use ZSH? ZSH is not only a tool to make terminal more "cool" with colors and themes?
• also, is there any difference between the Linux Terminal and the VSCode integrated terminal?
  Because it is the way to access the "kernel", right? So, if the kernel is the same for all these options, what is the difference between them?

[Mulling]

Hi, thank for joining in the discussion 🙏

The terminal, basically, is a program that receives output from other programs running on "top" of it, displays them on the screen and has it's own set of build in control commands called escape codes (it also handles font rendering and all that stuff). Most terminal emulators implement a set of theses commands and there are a lot of them. Usually it's some variation of the VT100 escape codes.

• Here are VT100 escape codes

You can use them for example to print colors, request a new buffer from the terminal, erase a line, move the cursor, Et cetera. Usually all terminal emulators support them, and you can make a lot of cool stuff with just that. Vim basically uses that.

The escape code below will color the line blue:

$ echo -e "\033[34mI'm Blue"

There are differences in the implementation of the Linux terminal and the one in VSCode, I don't know which set of escape codes VSCode supports and I think Linux supports VT110 (I don't remember from the top of my head). The terminal on the Linux kernel is also built into the kernel, VSCode is built using electron 🤮, but it is essentially doing the same thing.

The Shell, like the one you mentioned zsh, is another program running on "top" of the terminal. It takes input form the user, evaluates it, displays the result and loops back (REPL). When you open the terminal, the terminal will call your default shell in interactive mode. You can make it run other programs like:

$ st -e ls -R /

The command above will open the terminal I use, st, interpret the ls -R / command using the default shell, run it and exit. In this case it will list every thing in my computer and exit.

There are as well a lot of different shells, like: zsh, fish, bash, dash, mksh, Et cetera. Each has it's own scripting language and features, but there is a standard defined by POSIX. dash implements that standard. In turn It is more performant, but lacks useful and cool 😎 features.

If you still have questions, or something was not clear, please ask bellow.

Best regards,
Mulling

[Daniel-Boll]

TLDR;

The terminal emulator is just a GUI program you will use to interact with the shell. E.g.: gnome terminal, alacritty, st, VSCode's integrated terminal, kitty, etc.

The difference between them are mainly configurations and capabilities, some are also GPU accelerated.

The shell is a way to interact with Linux, where the difference is how they accomplish that, for example zsh has more complex glob expansions than bash, and shell.

Best regards,
Daniel Boll. 🎴