This project has been created as part of the 42 curriculum by juliosouza09 and avieira-42.

Minishell

Description

Minishell is a Unix shell implemented in C, developed as part of the 42 Common Core curriculum.

The goal of this project is to recreate the core behavior of Bash, focusing on:

• Process creation and control
• File descriptor management
• Signal handling
• Command parsing and execution
• Interaction with the UNIX operating system

This project demonstrates a strong understanding of systems programming, process lifecycle management, and low-level UNIX APIs, while enforcing strict constraints on allowed functions and global state.

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Features

Shell Behavior

• Interactive prompt display
• Command history using readline
• Executable resolution via PATH, relative paths, or absolute paths
• Correct exit status propagation ($?)

Parsing & Expansion

• Environment variable expansion ($VAR)
• Exit status expansion ($?)
• Single quotes (') to prevent all expansions
• Double quotes (") allowing $ expansion only
• Graceful handling of unsupported or unclosed syntax

Redirections

• < input redirection
• > output redirection
• >> output append redirection
• << heredoc with delimiter (without history update)

Pipes

• Full pipeline support using |
• Correct stdin/stdout chaining across commands

Built-in Commands

• echo (with -n)
• cd (relative or absolute path)
• pwd
• export
• unset
• env
• exit

Signal Handling

• ctrl-C → interrupts command and shows new prompt
• ctrl-D → exits the shell
• ctrl-\ → ignored (bash-like behavior)

Signal handling is implemented using at most one global variable, storing only the received signal number, ensuring safe separation between signal handlers and program state.

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Technical Constraints

• Written entirely in C
• Uses only authorized system calls and library functions
• No access to internal data structures from signal handlers
• No memory leaks in user-written code
• Uses libft where authorized

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Instructions

Compilation

make

Run

./minishell

Clean build files

make clean
make fclean

Recompile

make re

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What This Project Demonstrates

• Deep understanding of UNIX process management
• Safe and correct signal handling
• Robust file descriptor control
• Modular C design under strict constraints
• Ability to recreate complex system behavior from specifications

This project closely mirrors real-world shell behavior and provides strong foundations for backend, systems, and infrastructure engineering roles.

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Resources

Technical References

• Advanced Programming in the UNIX Environment — W. Richard Stevens
• Bash Reference Manual
• Linux man pages (fork, execve, pipe, dup2, wait, signal)
• GNU Readline Documentation

AI Usage Disclosure

AI tools were used only as a learning assistant, specifically for:

• Clarifying UNIX concepts (signals, pipes, process flow)
• Reviewing documentation references
• Improving code readability and documentation wording

All architecture decisions, implementation, debugging, and final code were written and validated manually.

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Notes

This project intentionally follows only the required specifications. When behavior was ambiguous, Bash was used as the reference implementation.

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Author

Júlio César 42 Porto — Software Development

• GitHub: https://github.com/juliosouza09
• LinkedIn: https://linkedin.com/in/juliosouzadev

Alexandre Soeiro 42 Porto - Software Development

• GitHub: https://github.com/avieira-42
• LinkedIn: https://linkedin.com/in/alexandre-soeiro-a6a57a197