Minishell

Welcome to Minishell, a simplified version of the Unix shell, built as a project to understand how shells work under the hood. This shell aims to replicate some of the basic functionalities of bash, including command execution, pipelines, redirections, and built-in commands, while adhering to specific project requirements.

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Table of Contents

• Features
• Installation
• Usage
• Built-in Commands
• Signal Handling
• Folder Structure
• Limitations
• Authors

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Features

• Display a prompt while waiting for user input.
• Command history navigation using arrow keys.
• Execution of commands with absolute, relative, or PATH-resolved paths.
• Environment variable expansion, including special variables like $?.
• Handle single and double quotes as in bash.
• Input/output redirections (<, >, >>, <<).
• Command pipelines using the pipe (|) operator.
• Built-in commands: echo, cd, pwd, export, unset, env, and exit.
• Proper signal handling for ctrl-C, ctrl-D, and ctrl-\.

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Installation

Requirements

• GCC compiler
• GNU Readline library - For Debian/Ubuntu-based Systems

  sudo apt-get install libreadline-dev

• Make

Steps

1. Clone the Repository

   git clone https://github.com/SaraitHernandez/minishell.git

2. Navigate to the Project Directory

   cd minishell

3. Compile the Program

   make

   This will generate the minishell executable in the root directory.

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Usage

Start the shell by running the executable:

./minishell

You should see a prompt like:

minishell$ 

Now you can start typing commands as you would in a regular shell.

Examples

• Running an External Command

  minishell$ ls -la

• Using a Built-in Command

  minishell$ cd /path/to/directory

• Pipelines

  minishell$ ls -la | grep minishell | wc -l

• Redirections

  • Output Redirection:

    minishell$ echo "Hello, World!" > hello.txt

  • Input Redirection:

    minishell$ wc -w < hello.txt

  • Append Output:

    minishell$ echo "This is appended text." >> hello.txt

  • Heredoc:

    minishell$ cat << EOF
    > This is a heredoc input.
    > EOF

• Environment Variable Expansion

  minishell$ echo "Current user: $USER"

• Exiting the Shell

  minishell$ exit

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Built-in Commands

echo

• Usage: echo [-n] [string ...]
• Options:
  • -n: Do not output the trailing newline.

cd

• Usage: cd [directory]
• Changes the current directory to directory.

pwd

• Usage: pwd
• Prints the current working directory.

export

• Usage: export [name[=value] ...]
• Sets environment variables.

unset

• Usage: unset [name ...]
• Unsets environment variables.

env

• Usage: env
• Prints the list of environment variables.

exit

• Usage: exit [n]
• Exits the shell with a status of n.

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Signal Handling

• ctrl-C (SIGINT): Displays a new prompt on a new line.
• ctrl-D (EOF): Exits the shell.
• ctrl-\ (SIGQUIT): Does nothing.

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Folder Structure

The project is organized into directories and files to enhance modularity and maintainability.

minishell/
├── Makefile
├── README.md
├── src/
│   ├── main.c
│   ├── init_shell.c
│   ├── input.c
│   ├── lexer.c
│   ├── expand_variables.c
│   ├── parser.c
│   ├── parser_utils.c
│   ├── executor.c
│   ├── exec_utils.c
│   ├── redirection.c
│   ├── pipes.c
│   ├── signals.c
│   ├── cleanup.c
│   ├── globals.c
│   ├── builtins/
│   │   ├── builtin_echo.c
│   │   ├── builtin_cd.c
│   │   ├── builtin_pwd.c
│   │   ├── builtin_export.c
│   │   ├── builtin_unset.c
│   │   ├── builtin_env.c
│   │   └── builtin_exit.c
│   ├── environment/
│   │   ├── environment.c
│   │   └── environment_utils.c
│   └── utils/
│       ├── utils_strings.c
│       ├── utils_memory.c
│       └── utils_errors.c
├── includes/
│   └── minishell.h
└── libft/
    └── [Your libft files or linked library]

Explanation of Folders and Files

Makefile

• Automates the compilation process.
• Contains rules to build, clean, and rebuild the project.

README.md

• The document you're reading now.
• Provides an overview and instructions.

src/

• Core Source Files

  • main.c
    • Entry point of the shell program.
  • init_shell.c
    • Initializes the shell environment and signal handlers.
  • input.c
    • Handles user input and command history.
  • lexer.c
    • Tokenizes the input command line.
  • expand_variables.c
    • Expands environment variables in tokens.
  • parser.c
    • Parses tokens into an abstract syntax tree (AST).
  • parser_utils.c
    • Utility functions for the parser.
  • executor.c
    • Executes commands based on the AST.
  • exec_utils.c
    • Utility functions assisting in command execution.
  • redirection.c
    • Manages input/output redirections.
  • pipes.c
    • Handles piping between commands.
  • signals.c
    • Manages signal handling for the shell.
  • cleanup.c
    • Frees allocated resources before exiting.
  • globals.c
    • Contains the allowed global variable for signal indication.

• Built-in Commands (builtins/)

  • Each built-in command is implemented in its own file for clarity and modularity.
  • builtin_echo.c
  • builtin_cd.c
  • builtin_pwd.c
  • builtin_export.c
  • builtin_unset.c
  • builtin_env.c
  • builtin_exit.c

• Environment Management (environment/)

  • Manages environment variables for the shell.
  • environment.c
    • Functions to manipulate environment variables.
  • environment_utils.c
    • Utility functions for environment management.

• Utilities (utils/)

  • General-purpose helper functions used across the project.
  • utils_strings.c
    • String manipulation functions.
  • utils_memory.c
    • Memory allocation and management functions.
  • utils_errors.c
    • Error reporting and handling functions.

includes/

• Contains all header files.
• minishell.h
  • Main header file with structure definitions, function prototypes, and macros.

libft/

• Your custom library of standard functions (if applicable).
• Include or link your libft library here.

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Limitations

While minishell replicates many features of bash, there are some limitations:

• No Wildcard Expansion
  • Patterns like *.c won't be expanded automatically.
• Limited Error Messages
  • Error messages may not be as descriptive as those in bash.
• No Job Control
  • Background job management (&, fg, bg, etc.) is not implemented.
• No Advanced Shell Features
  • Features like command substitution, shell scripting, or functions are not supported.
• No Support for Special Characters
  • Characters like backslash (\) or semicolon (;) are not interpreted.

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Authors

• Sarait Hernández - GitHub
• Artur Kacprzycki - GitHub

Feel free to contact us for any questions or suggestions!

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Thank you for using Minishell! We hope this project helps you understand the inner workings of a shell and provides a solid foundation for further exploration.

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Notes

• Contributions: If you'd like to contribute to this project, please fork the repository and submit a pull request.
• License: This project is for educational purposes and may not be used for commercial applications.
• Acknowledgments: Thanks to the resources and community that provided guidance throughout this project.