Minishell

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Project Overview

The Minishell project from 42 School introduces:

• The fundamentals of shell programming
• Process creation, pipes, and redirections
• Handling signals, environment variables, and built-in commands

This project is all about recreating a simplified version of the Bash shell —
learning how a real shell parses commands, executes processes, and manages the environment 🐚

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📚 Learning Goals

• Master process control with fork, execve, and wait
• Implement I/O redirections and pipes
• Manage signals like ctrl+C, ctrl+D, and ctrl+\
• Handle environment variables dynamically
• Build a modular, robust, and readable C program

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🧠 Design Choices

The project is structured with a clear separation between parsing and execution.

• Parsing is responsible for:

  • Tokenizing user input
  • Handling quotes
  • Expanding environment variables
  • Building clean command structures

• Execution only works with already parsed and expanded commands.

This design avoids mixing string manipulation logic with process control, making the code easier to debug, extend, and reason about.

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🧩 Work Distribution

Fabio Vitharana

• Parsing layer implementation
• Tokenization and syntax analysis
• Quote handling and variable expansion
• Built-in command logic

Ilaria Nassi

• Execution layer implementation
• Process creation and management
• Pipes and redirections handling
• Signal handling and exit status management

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🏗️ Architecture Overview

Below is a simplified view of how Minishell processes a command:

┌──────────────────────────────────────────┐
│               User Input                 │
└──────────────────────────────────────────┘
                     │
                     ▼
┌──────────────────────────────────────────┐
│               Parsing Layer              │
│  • Tokenization                          │
│  • Syntax checking                       │
│  • Environment variable expansion         │
└──────────────────────────────────────────┘
                     │
                     ▼
┌──────────────────────────────────────────┐
│              Execution Layer             │
│  • Handle built-ins                      │
│  • Set up pipes and redirections         │
│  • Create processes with fork/execve     │
│  • Wait for children and manage status   │
└──────────────────────────────────────────┘
                     │
                     ▼
┌──────────────────────────────────────────┐
│              Shell Loop                  │
│  • Display prompt                        │
│  • Handle signals                        │
│  • Repeat until exit                     │
└──────────────────────────────────────────┘

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🔍 Expansion Behavior

Environment variable expansion is handled during the parsing phase, before command execution.

• Variables are expanded using $VAR
• $? expands to the last command exit status
• No expansion occurs inside single quotes
• Expansion is allowed inside double quotes
• Heredoc delimiters are not expanded

By resolving expansions early, the execution layer only deals with final strings.

👩‍💻 Authors

• Ilaria Nassi @19Jillian89
• Fabio Vitharana @FabzHub17

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📄 License

This project is for educational purposes only and is part of the 42 Common Core curriculum. 42 Common Core curriculum,

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