🐚 NovaShell — High-Performance Custom Unix Shell

NovaShell is a feature-rich, high-performance Unix-like command shell implemented in C. Demonstrating low-level operating system fundamentals including process management (`fork`, `execvp`), inter-process communication (pipes), IO redirection, safety guards, and real-time CPU/memory resource monitoring.

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🌟 Key Features

• ⚡ Process Lifecycle Management: Fast process spawning with fork(), execvp(), and non-blocking background job handling (&).
• 📁 Builtin Shell Navigation: Full cd support (including ~ home expansion and cd - directory toggle), pwd, and help.
• 🔀 Inter-Process Communication: Pipeline execution (cmd1 | cmd2) connecting stdout to stdin via Unix pipes.
• 📤📥 File IO Redirection: Supports stdout truncation (>), stdout append (>>), and stdin input redirection (<).
• 🛡️ Safety Lockdown Layer: Intercepts and blocks destructive root commands (rm -rf, shutdown, reboot).
• 💡 Typo Suggestion Engine: Intelligent command recommendation for mistyped utility names.
• 📊 Real-Time Resource Monitoring: Live visual CPU/memory usage bars, wall-clock timing, and performance badges (FAST, NORMAL, SLOW).
• 📜 Session History & Analytics: Builtin command history tracking and exit session performance summary.

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🏗️ Architecture & Component Overview

  NovaShell Core Architecture
  ├── src/main.c      - Command loop, builtin dispatcher, env expansion, IO redirection
  ├── src/pipe.c      - Inter-process pipe handler (`dup2`, `pipe`)
  ├── src/monitor.c   - Real-time CPU & memory consumption tracker (`getrusage`, `gettimeofday`)
  ├── src/safety.c    - Danger interception layer (`rm -rf` guard)
  ├── src/history.c   - Circular command history buffer
  ├── src/suggest.c   - Levenshtein-based command suggestion engine
  └── src/summary.c   - Session statistics & command counters

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🛠️ Build & Installation Guide

Prerequisites

• GCC / Clang compiler supporting C99 standard
• GNU Make

Compilation

# Clone or navigate to directory
cd nova-shell

# Compile project using Makefile
make

# Execute NovaShell
./build/nova-shell

Clean Build Artifacts

make clean

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💻 Interactive Commands & Usage Syntax

Feature	Example Command	Description
Directory Navigation	cd ~/Projects	Change directory (cd - to return to previous path).
Print Directory	pwd	Print current working directory.
Pipeline Execution	ls -la | grep txt	Pipe output from command 1 into command 2.
Output Redirection	echo "Hello" > out.txt	Truncate and write to file.
Append Redirection	echo "Line 2" >> out.txt	Append text to file.
Input Redirection	cat < out.txt	Read stdin from input file.
Background Execution	sleep 10 &	Execute task asynchronously in background.
Command History	history	List recent command execution history.
Help Manual	help	Display builtin command manual.
Exit Shell	exit	Output session telemetry summary and terminate shell.

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🧪 Testing Verification

# Test 1: Navigation & Env Expansion
nova-shell [~/Projects/nova-shell]> cd ~
nova-shell [~]> pwd
/Users/username

# Test 2: Pipe & Redirection
nova-shell [~/Projects/nova-shell]> echo "NovaShell Enterprise" > test.txt
nova-shell [~/Projects/nova-shell]> cat test.txt | grep Nova
NovaShell Enterprise

# Test 3: Safety Layer
nova-shell [~/Projects/nova-shell]> rm -rf /
⚠️ Safety Alert: Dangerous command blocked for system security.

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👨‍💻 Developer & Attribution

Developed by Om Srivastava (@IronLad123)
B.Tech in Computer Science & Engineering (Specialization in Data Science)