A minimal, POSIX-compliant Unix-style shell for Linux distributions.

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Table of Contents

• Overview
• Features
• Architecture
• Build
• License
• Author

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Overview

MiniShell is a lightweight Linux shell written in C++ from the ground up. Command parsing, process forking, pipe chaining, I/O redirection, and signal handling — all in a clean, readable codebase..

mnsh:~$ echo "Hello, Shell!" | tr '[:lower:]' '[:upper:]'
"HELLO, SHELL!"
mnsh:~$ _

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Features

• Execution of external commands using fork, execvp, and waitpid.
• Abstract Syntax Tree (AST) – based parsing for complex command structures.
• Logical operators:
  • && (AND)
  • || (OR)
• Sequence - ;
• Pipelines using - |
• Input/output/error redirections:
  • <, >, >>, 2>
• Subshell support using parentheses ( ... ) with correct scope isolation.
• Built-in commands like cd, exit, etc.
• Accurate exit-status propagation enabling correct short-circuit logic.
• Parent/child process separation for built-ins and subshells.
• Signal handling: Supports Ctrl+C interruption for foreground commands and subshell execution, with signal isolation between parent shell and child processes.
• Line editing & history (↑↓ navigate, ←→ cursor, Ctrl+A/E, Tab completion, history, !n)

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Architecture

The shell follows a modular design:

Tokenizer → Parser → AST → Executor

• Tokenizer

  Converts raw input into tokens (commands, operators, redirections, parentheses).

• Parser

  Builds an AST respecting operator precedence:

  ; → lowest
  && and ||
|
  command/subshell → highest

• AST Nodes

  • Command
  • Pipeline
  • Logical
  • Sequence
  • Subshell

• Executor

  • Recursively evaluates AST nodes using post-order traversal
  • Forks processes where required
  • Preserves shell state for built-ins

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Build

# Ubuntu / Debian
sudo apt install build-essential
mkdir build
cd build
cmake ..
make
./mnsh  or gnome-terminal -- ./mnsh (for new tab in terminal)

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License

Distributed under the MIT License. See LICENSE for details.

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Author

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