Nush Unix Shell

Overview

Nush (Northeastern University Shell) is a custom Unix Shell designed to provide a command-line interface with support for executing external programs, bash built-in commands, and operators. It supports interactive mode and script file execution, making it a powerful tool for both manual and automated command execution.

This project was the first challenge assignment for CS3650 Computer Systems at Northeastern University.

Features

• Command Execution:
  • Run external programs and built-in commands.
  • Support for operators and multi-process execution.
• Scripting Support:
  • Execute commands from script files for automation.
• Interactive Mode:
  • Engage with a user-friendly interactive prompt.
• Redirection and Pipes:
  • Input/output redirection (<, >, >>).
  • Pipe multiple commands together (|).
• Background Processes:
  • Execute commands in the background using the & operator.
• Error Handling:
  • Provide meaningful error messages for syntax and execution failures.
• Signals and Signal Handling:
  • Gracefully handle exit and signals like Ctrl+C.
• Job Control:
  • Basic job control features, including foreground and background processes.

Usage

Interactive Mode

Run the shell in interactive mode:

$ ./nush

Script File Execution

Execute commands from a script file:

$ ./nush tests/01-echo-one.sh

Examples

• Run an external command:

  nush$ echo hello
  

• Execute a built-in command:

  nush$ cd /path/to/directory
  

  nush$ pwd
  

• Redirect input/output:

  nush$ head -n 2 < test.txt
  nush$ echo one > test.txt
  

• Run commands in the background:

  $ command1 & command2
  

• Pipeline Operator

  nush$ sort sample.txt | uniq
  

• And Operator

  nush$ true && echo true
  nush$ echo one && echo two
  

• Or Operator

  nush$ false || echo false
  nush$ echo one || echo two
  

• Semicolon Operator

  nush$ echo one; cat sample.txt
  

• Variables

  nush$ FOO=one
  nush$ BAR=two
  nush$ echo $FOO $BAR $FOO
  nush$ FOO=three
  nush$ echo $BAR $FOO $BAR
  

Installation

Clone the repository:

$ git clone https://github.com/tiingweii-shii/Nush-Unix-Shell

Navigate to the nush directory:

$ cd path-to-repository/nush

Compile the shell:

$ make

Run the shell:

$ ./nush

To exit the shell:

nush$ exit