Minishell

Description

minishell is a C project that implements a small Unix-like shell with parsing, expansion, redirections, pipelines, and command execution.

This codebase also parses and executes logical operators (&&, ||) and parenthesized command groups.

Features

• Interactive shell loop with readline history support.
• Non-interactive mode (commands can be piped to stdin).
• Builtins: cd, pwd, echo, env, export, unset, exit.
• Environment variables stored in an internal linked list.
• Variable expansion ($VAR, $?) and expansion inside double-quoted strings.
• Redirections: <, >, >>, << (heredoc).
• Pipelines built around fork, pipe, dup2, and execve.
• Wildcard expansion for * against entries in the current directory (dotfiles only when the pattern starts with .).
• Logical operators &&, ||, and parenthesized command groups.

How it works

1. The main loop reads a line, initializes runtime state, and dispatches parsing/execution.
2. The parser tokenizes input into a linked list (t_word) and runs syntax checks (pipes, redirections, logic tokens, parenthesis).
3. Pre-execution steps handle heredocs, variable expansion, wildcard expansion, and token joins.
4. Execution chooses between builtin dispatch in-process and external commands via fork + execve, with redirections/pipes applied through fd duplication.
5. Exit status is tracked globally and reused by conditional execution.

Installation / Build

Requirements

• cc (C compiler)
• make
• readline development/runtime library

Build commands

make

Other available targets:

make clean
make fclean
make re

The build produces the executable:

./minishell

Usage

Interactive mode:

./minishell

Non-interactive mode:

printf 'echo hello_from_minishell\nexit\n' | ./minishell

Example

./minishell
echo "User: $USER"
ls -la | grep src > out.txt
cat out.txt
exit

Tested non-interactive smoke example output:

hello_from_minishell

Project Structure

include/
  minishell.h            # Core types, tokens, prototypes
libft/                   # Internal 42 utility library
src/
  main/                  # Shell loop, prompt, signal setup
  env/                   # Environment linked-list management
  parsing/               # Tokenization and syntax checks
  expand/                # Variable and wildcard expansion
  exec/                  # Heredoc prep, redirections, pipelines, execution
  builtins/              # Builtin command implementations
  free_and_exit/         # Cleanup and exit utilities
  git/                   # Prompt git branch/dirty-state helpers
tester/                  # Local test scripts/assets
Makefile

What I learned

• Designing a shell around linked-list based token streams and explicit execution phases.
• Implementing process orchestration with fork, execve, pipes, redirections, and wait status handling.
• Building parsing/syntax checks for shell grammar edge cases.
• Managing shell state (environment, exit code, signals, heredoc behavior) consistently across parent and child processes.