About

This project is about creating a lightweight version of bash (Born Again Shell).

Features

• prompts user for input
• checks user input for valid commands else returns appropriate errors
• executes commands with options (Ex: ls -l)
• handles multiple pipes (Ex: ls | head -2 | wc)
• custom built-ins (cd, pwd, echo, unset, export, env)
• I/O redirections (<, >, <<, >>)
• handles signals (Ctrl-C, Ctrl-D, Ctrl-)

What I learned

• UNIX programming in general
• bash's behaviour in various situations and how it is implemented
• How to create processes and retrieve valuable informations from them. Like exit codes
• How to create a pipeline that handles I/O redirections
• How to analyze files

Tips & Tricks

• Use the lsof -c <name_of_your_program> or ps aux | grep program_name commands to see the current processes of a specific program

Useful Links

Tutorials

• Tutorial - Write a Shell in C by Stephen Brennan
• Let's Build a Command Line Shell in C
• Multipipe_tutor
• Pipe: an Inter-Process Communication Method

Manuals

• Systems Programming : Chapter 5 : Writing Your Own Shell
• The Shell Command Language
• Bash Reference Manual