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minishell

A bash shell implementation built as part of the 42 School curriculum. minishell replicates core bash functionality including built-in commands, environment variable expansion, pipes, redirections, and signal handling.

This project is written in C and provides a functional command-line interface similar to bash.

🚀 Features

Core Functionality

  • Built-in Commands: echo, cd, pwd, export, unset, env, exit
  • Environment Variable Expansion: Handles $VAR syntax with full quoting support
  • Command Chaining: Pipes (|) for command composition
  • File Redirections: Input/output redirection (>, <, >>, <<)
  • Heredocs: Multi-line input processing
  • Signal Handling: Ctrl-C, Ctrl-D, Ctrl-\ with proper cleanup
  • Interactive Shell: Real-time command execution with prompt

Advanced Features

  • Quoting System: Single quotes (literal) and double quotes (with expansion)
  • Process Management: Proper fork/exec with signal inheritance
  • File Descriptor Management: Automatic cleanup and redirection
  • Error Handling: Graceful error recovery and meaningful messages

🚀 Getting Started

Prerequisites

  • gcc (GNU Compiler Collection)
  • make (Build automation tool)
  • Linux (Tested on Ubuntu/Debian)

Building

git clone https://github.com/tasmanday/minishell.git
cd minishell
make

Running

./minishell

Cleaning

make fclean

🖥️ Usage Examples

# Basic functionality
echo "Hello World"
cd /tmp && pwd

# Environment variables
export TEST_VAR="test"
echo $TEST_VAR

# Pipes and redirections
echo "test" | grep "test"
echo "hello" > test.txt
cat < test.txt

# Signal handling
# Press Ctrl-C to test interrupt handling

📋 Built-in Commands

Command Options Description
echo -n Print text with optional newline suppression
cd path Change directory (relative or absolute path)
pwd none Print working directory
export none Export environment variables
unset none Unset environment variables
env none Display environment variables
exit none Exit the shell

⚙️ Technical Details

Environment Variables

  • Expand variables using $VAR syntax
  • Set and unset environment variables
  • Export variables to child processes

Quoting

  • Single quotes: Literal text, no expansion
  • Double quotes: Allow variable expansion
  • Handles nested quotes appropriately

Redirections

  • > : Output redirection (overwrite)
  • >> : Output redirection (append)
  • < : Input redirection
  • << : Heredoc (multi-line input)

Pipes

  • Chain commands with |
  • Support for multiple pipes in sequence
  • Proper file descriptor management

Signal Handling

  • Ctrl-C (SIGINT): Interrupt current command
  • Ctrl-D (EOF): Exit shell gracefully
  • Ctrl-\ (SIGQUIT): Quit with core dump

⚡ Architecture

  • Lexical Analysis: Parse input into tokens
  • Command Parsing: Identify built-ins vs external commands
  • Environment Management: Handle variable expansion and inheritance
  • Process Management: Fork and execute commands
  • File Descriptor Management: Handle pipes and redirections
  • Signal Handling: Manage shell and child process signals

📋 Project Limitations

Compilation Requirements

  • Compiler Flags: Must compile with -Wall -Wextra -Werror
  • No Re-linking: Makefile must not re-link unnecessarily
  • Error-Free Compilation: No compilation errors or warnings allowed

Code Restrictions

  • Global Variables: Limited to one global variable for signal handling only
  • Authorized Libraries: Only libft (our custom library) is allowed
  • External Functions: Limited to specific authorized functions only

Allowed External Functions

  • Interactive Input: readline, rl_clear_history, rl_on_new_line, rl_replace_line, rl_redisplay, add_history
  • Standard I/O: printf, write, access, open, read, close
  • Memory Management: malloc, free
  • Process Control: fork, wait, waitpid, wait3, wait4, signal, sigaction, sigemptyset, sigaddset, kill, exit
  • File System: getcwd, chdir, stat, lstat, fstat, unlink, execve
  • File Descriptors: dup, dup2, pipe
  • Directory Operations: opendir, readdir, closedir
  • Error Handling: strerror, perror
  • Terminal Control: isatty, ttyname, ttyslot, ioctl, getenv, tcsetattr, tcgetattr
  • Terminal Capabilities: tgetent, tgetflag, tgetnum, tgetstr, tgoto, tputs

Makefile Requirements

  • Required Targets: NAME, all, clean, fclean, re
  • Submission Files: Makefile, *.h, *.c

🛠️ Made With

  • C - Core implementation language
  • Make - Build system
  • Linux - Target platform
  • libft - Custom C library for utility functions

🤝 Contributors