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0-Shell

Overview

In this project, you’ll build 0-shell, a minimalist Unix-like shell implemented in Rust, designed to run core Unix commands using system calls—without relying on external binaries or built-in shells like bash or sh.

Inspired by tools like BusyBox, this project introduces you to key concepts in Unix system programming, including process creation, command execution, and file system interaction, all while leveraging Rust’s safety and abstraction features to avoid manual memory management.

Role Play

You are a system-level developer assigned to build a lightweight, standalone Unix shell for an embedded Linux environment. Your task is to create a shell that handles basic navigation, file manipulation, and process control—faithfully mimicking essential shell behaviors without relying on existing shell utilities.

Learning Objectives

• Work with file and directory operations
• Manage user input and output within a shell loop
• Implement robust error handling
• Gain experience in Unix process and system call APIs

Core Requirements

Your minimalist shell must:

• Display a prompt ($ ) and wait for user input
• Parse and execute user commands
• Return to the prompt only after command execution completes
• Handle Ctrl+D (EOF) gracefully to exit the shell

You must implement the following commands from scratch, using system-level Rust abstractions:

• echo
• cd
• ls (supporting -l, -a, -F)
• pwd
• cat
• cp
• rm (supporting -r)
• mv
• mkdir
• exit

Additional constraints:

• Do not use any external binaries or system calls that spawn them
• If a command is unrecognized, print:
  Command '<name>' not found

Constraints

• Only basic command syntax is required
  (No piping |, no redirection >, no globbing *, etc.)
• Shell behavior should align with Unix conventions
• Code must follow good coding practices

Bonus Features

Implementing any of the following will be considered bonus:

• Handle Ctrl+C (SIGINT) without crashing the shell
• Shell usability enhancements:
  • Auto-completion
  • Command history
  • Prompt with current directory (e.g., ~/projects/0-shell $)
  • Colorized output for commands, directories, and errors
  • Command chaining with ;
  • Pipes (|)
  • I/O redirection (>, <)
• Support for environment variables (e.g. $HOME, $PATH)
• A custom help command documenting built-in functionality

Example Usage

student$ ./0-shell
$ cd dev
$ pwd
/dev
$ ls -l
total 0
crw-------  1 root   root     10,    58 Feb  5 09:21 acpi_thermal_rel
crw-r--r--  1 root   root     10,   235 Feb  5 09:21 autofs
drwxr-xr-x  2 root   root           540 Feb  5 09:21 block
...
$ something
Command 'something' not found
$ echo "Hello There"
Hello There
$ exit
student$

Evaluation Criteria

This project will be reviewed and graded based on the following:

• Functionality: Commands perform correctly and emulate standard Unix behavior
• Stability: Shell handles user errors, invalid input, and edge cases without crashing

Resources

• man pages (e.g., man 2 open, man 2 execve)
• Unix Shell - Wikipedia
• BusyBox
• Rust std::fs and std::process Docs