minishell

[42-Cursus] Minishell is a minimalist shell implementation written in C, designed to mimic basic functionalities of a Unix shell like Bash. This project focuses on understanding processes, file descriptors, and shell operations such as command execution, redirections, pipes, and signal handling.

Keywords

• Shell
• Process Management
• File Descriptors
• Redirections
• Pipes
• Signal Handling
• Built-in Commands
• Environment Variables

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Index

• Overview
• Features
• Bonus Features
• Requirements
• How to Run
  • Example Usage
  • Bonus Usage
  • Error Handling
• What I Learned
• Author
• Acknowledgments

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Overview

Minishell is a simplified Unix shell implementation created as part of the 42 Cursus curriculum. The project aims to deepen understanding of core operating system concepts such as process management, file descriptors, and shell operations. Minishell supports basic shell functionalities like command execution, input/output redirection, pipes, and environment variable management. It also handles signals like ctrl-C, ctrl-D, and ctrl-\ similar to Bash.

The project is written in C and adheres to strict coding standards, ensuring no memory leaks and robust error handling. Minishell is a great way to explore the inner workings of a shell and gain hands-on experience with low-level system programming.

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Features

• Command Execution: Executes commands based on the PATH variable or using relative/absolute paths.
• Input/Output Redirection: Supports <, >, <<, and >> for input/output redirection.
• Pipes: Implements pipes (|) to connect the output of one command to the input of another.
• Environment Variables: Expands environment variables (e.g., $HOME) and $? for the exit status of the last command.
• Signal Handling: Handles ctrl-C, ctrl-D, and ctrl-\ as in Bash.
• Built-in Commands: Implements built-ins like echo, cd, pwd, export, unset, env, and exit.
• Quoting: Handles single (') and double (") quotes to prevent interpretation of metacaracters.

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Bonus Features

• Logical Operators: Supports && and || with parentheses for priority.
• Wildcards: Implements * wildcard for the current directory.

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Requirements

• The project must be written in C and follow the 42 Norm.
• No memory leaks are allowed.
• The shell must handle signals correctly and manage file descriptors properly.
• The Makefile must compile the project with -Wall, -Werror, and -Wextra flags.
• The shell must support the mandatory features listed in the subject.

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How to Run

1. Clone this repository:

   git clone [repository-url]  
   cd minishell  

2. Compile the project:

   make  

3. Run the shell:

   ./minishell  

Recommendations for Testing

• Use valgrind to check for memory leaks:

  valgrind --leak-check=full --show-leak-kinds=all ./minishell  

• Test with various commands, redirections, and pipes to ensure proper functionality.

Parser Example

Input:

cat < in | grep "Hi bye" | grep 'M' > out | cat >> final_out -e

Tokenizer result and classification:

• "cat": command
• "<": redir_in
• "in": file_path
• "|": op_pipe
• "grep": command
• "Hi bye": argument
• "|": op_pipe
• "grep": command
• "M": argument
• ">": redir_out
• "out": file_path
• "|": op_pipe
• "cat": command
• ">>": redir_append
• "final_out": file_path
• "-e": argument

Example Usage

Input Command	Description	Expected Output
echo Hello World	Prints "Hello World" to the terminal.	Hello World
ls -l	Lists files in the current directory in long format.	List of files in long format.
cat < file.txt	Reads content from file.txt.	Content of file.txt.
`ls	grep .c`	Lists files and filters those ending with .c.
export VAR=value	Sets an environment variable VAR to value.	No output, but VAR is set.
cd /path/to/directory	Changes the current directory.	No output, but directory changes.

Bonus Usage

For bonus features, use the bonus rule in the Makefile:

make bonus

Input Command	Description	Expected Output
ls *.c	Lists all .c files in the current directory.	List of .c files.
echo Hello && echo World	Executes echo Hello and echo World sequentially.	Hello followed by World.
`echo Hello		echo World`

Error Handling and Testing

Input Command	Description	Expected Output
cat nonexistent_file	Attempts to read a non-existent file.	Error: No such file or directory
cd /invalid/path	Attempts to change to an invalid directory.	Error: No such file or directory
echo "Unclosed quote	Attempts to execute a command with an unclosed quote.	Error: Unclosed quote

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What I Learned

• Process Management: Gained a deeper understanding of how processes are created and managed using fork, execve, and waitpid.
• File Descriptors: Learned how to manipulate file descriptors for input/output redirection and piping.
• Signal Handling: Implemented signal handling for ctrl-C, ctrl-D, and ctrl-\.
• Environment Variables: Managed environment variables and their expansion in commands.
• Error Handling: Developed robust error handling to manage invalid commands, file operations, and memory allocation.

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Authors

• Name: Oliver King Zamora

• GitHub: oliverkingz

• 42 Login: ozamora-

• Name: Raúl José Pérez Medina

• GitHub: RaulPerezDEV

• 42 Login: raperez-

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Acknowledgments

This project is part of the 42 Cursus, a rigorous programming curriculum that emphasizes hands-on learning and problem-solving. Special thanks to the 42 team for providing this challenging and rewarding project!
Also thanks to peers and mentors for their feedback and support during the development process.

• 42 Community: For the collaborative environment and peer reviews.
• Bash: Used as a reference for shell behavior and functionality.