[the__alchemist]

Does anyone have an ELI5 for what this, BASH, ZSH, Powershell etc do? It seems it's a conflation of #1: A CLI. #2: A specialized programming language that mainly does file-system operations. Is there a compelling reason to use something like this (or Powershell's scripting system, from the comments here), vice Python or Rust's etc standard library filesystem tools?

Context: I use Windows Terminal with embedded powershell on Windows, and Terminal on Linux. Useful for compiling programs, running Python scripts, and executing CLI-based programs (eg clippy, ipython, rust, various programming-language-specific formatters etc, some CLI-based text editors like VIM). Also, troubleshooting Linux problems.

[BoppreH]

Shells are a combination of programming language, user interface, and standard library. The programming language and stdlib aspects are just like Python or Rust, but with a different focus:

- Terseness. I can very realistically type hundreds, if not thousands, of commands per day. Extra words or punctuation marks add up quickly.

- Shells are focused on executing things right now, as opposed to most other languages where the output is an abstract program to be run multiple times. This means using literals more often than variables, for example, which is why unquoted words in Bash are strings (except the first word of a command, because terseness is more important than consistency).

- They have more interactive features, such as warnings and prompts. Powershell detects if you're missing required params and prompts you one by one, for example.

- The purpose of a shell is to enable interactivity with OS primitives, be they Linux's files/processes or Windows' objects.

- Because most commands are typed interactively and only run once, glue code is especially painful and wasteful to write. So these languages pick a simple data structure for all function communication, and stick with it (e.g. Powershell's typed objects, Bash's newline separated strings, Lua's everything-is-a-table).

- Quality-of-life features. For example, Bash aliases (e.g. `alias wget='wget -c '`) are a pretty good idea that is non-trivial in other programming languages.

- Easy to plug stuff into other stuff. I don't mean just piping, but also things like temporary files via Bash's process substitution `<()`.

[the__alchemist]

Very clear explanation; thank you!

[raydiatian]

A shell is pretty much what you described. More accurately it’s a program for interacting with the operating system, and it usually ships with a scripting language, and Utility programs. Hence the conflation.

If you’re using Windows Terminal, you’re using a sort of predecessor to Powershell (somebody please correct me on this), if you’re using terminal on Linux, you’re most likely using bash. Enter ps -p $$ at your Linux terminal to find out (which shell you’re using).

> Useful for compiling programs, running Python scripts, and executing CLI-based programs

Yeah, so from here, it’s possible to automate those commands, if you wanted to. In windows you’re talking about .Bat or .Ps1 files. Shells are the language you use to write those scripts, and they typically ship with access to some useful (file/text oriented) commands.

The only problem is these shells were invented in the 80s 90s, and have awful conventions that make some people miserable enough that they go and write a new shell that tosses previous conventions out the window. And IMO they did a great job.

[ripley12]

> If you’re using Windows Terminal, you’re using a sort of predecessor to Powershell (somebody please correct me on this)

Not necessarily. Windows Terminal is just a terminal emulator; you can run any shell in it: cmd.exe, PowerShell, Nushell, bash, fish...

[deafpolygon]

And what a great Terminal emulator it is.

[ripley12]

Agreed; it’s a massive step forward for Windows and the team behind it is great.

[deafpolygon]

It blows my mind that they have a proper team behind WT now (for a while now), and it has already (in my mind) surpassed MacOS Terminal (unchanged for years) and most of Linux Terminal Emulators.

If Microsoft can just get a proper team behind the other tech...

[raydiatian]

Oh shit. I’m thinking of command prompt.

[the__alchemist]

Appreciate those details! And as ripley said, Windows Terminal is a housing for other terminals like Powershell or various WSL OSes, but has tabs.

[zacmps]

Yes, scripting languages all support both:

* A repl for performing common operations (moving around the file system, running programs, etc),

* A interpreted environment for scripting these operations.

The main reason to use these instead of Python/Rust is the ease of interfacing with other programs.

In Python, and most other non-scripting languages, spawning and interacting with external processes is quite verbose.

[the__alchemist]

It's verbose in Rust too; error handling; various types ways to handle the program's stdout/stderr etc.