This project has been created as part of the 42 curriculum by mkhandaq, aalemami.

minishell

Description

This project is a custom Unix-like shell written in C as part of the 42 curriculum.

Its goal is to reproduce the core behavior of a real shell while learning low-level system programming concepts such as process creation, signal handling, file descriptor manipulation, parsing, and environment management.

At a high level, this minishell:

• reads commands in interactive mode (Readline) and non-interactive mode (stdin stream),
• tokenizes input with quote awareness,
• validates syntax (including operators and brackets),
• builds an execution tree (AST) using operator precedence,
• performs expansions (environment variables, $?, wildcard *),
• handles redirections (<, >, >>, <<),
• executes built-ins and external binaries,
• propagates exit status across pipelines, logical operators, and subshells.

Implemented Features

• Built-ins: echo, cd, pwd, export, unset, env, exit
• Operators: |, &&, ||
• Grouping with parentheses for subshell execution
• Redirections: input, output, append, heredoc
• Environment expansion: $VAR and $?
• Wildcard expansion for * patterns in the current directory
• Signal behavior for interactive shell and heredoc interruption

Notes

• In non-interactive mode, the shell prints exit when stdin reaches EOF.
• Wildcard support is focused on * matching.

Instructions

Prerequisites

• A C compiler (cc/gcc)
• make
• Readline development library (for example, libreadline-dev on Debian/Ubuntu)

Build

make

Run

Interactive:

./minishell

Non-interactive examples:

echo "pwd" | ./minishell
printf "echo hello\nexit\n" | ./minishell

Clean Artifacts

make clean
make fclean
make re

Resources

Classic references related to shell implementation and Unix process control:

• 42 minishell subject and project guidelines (intra)
• GNU Bash Reference Manual: https://www.gnu.org/software/bash/manual/
• POSIX Shell Command Language: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
• Linux man pages: fork(2), execve(2), waitpid(2), pipe(2), dup2(2), open(2), signal(2), readline(3)

AI Usage

AI was used as a support tool for:

• Helping creating this README file.
• Explaining some of the shell concepts.

All implementation decisions, code integration, and final validation were performed manually in the project codebase.