ShX – A Lightweight POSIX Shell in Go

ShX is a minimalistic, POSIX-compliant command-line shell written in Go. It interprets and executes both built-in commands and external programs, providing a functional and efficient shell experience.

This project is a great learning resource for command parsing, REPL (Read-Eval-Print Loop), process management, and shell scripting.

Features

✅ Built-in Commands

Supports essential commands like cd, pwd, echo, exit, and type.

✅ External Command Execution

Runs system executables found in $PATH.

✅ Command Parsing

Handles single & double quotes, escaping (\), and arguments.

✅ Redirection Operators

> / 1> : Overwrite stdout.
>> / 1>> : Append to stdout.
2> : Overwrite stderr.
2>> : Append to stderr.

✅ Autocompletion

Single Tab: Auto-completes when there’s a unique match or common prefix.
Double Tab: Lists all possible matches if multiple exist.

✅ Customized Prompt

Displays a green ShX prompt with an arrow (➜) before input:
```
fmt.Fprint(os.Stdout, "\r\033[1;32mShX\033[0m ➜ ")
```

Installation

Prerequisites

Ensure Go is installed. Install Go.

Clone & Build

git clone https://github.com/ShreyamKundu/ShX.git
cd ShX/cmd/
go build -o ShX main.go

Usage

Start ShX by running:

./ShX

You'll see a prompt:

ShX ➜

Now you can enter commands.

1. `echo` – Print Messages

Basic Usage

ShX ➜ echo Hello, ShX!
Hello, ShX!

With Quotes

ShX ➜ echo 'Hello, ShX!'
Hello, ShX!

With Escape Characters

ShX ➜ echo Hello\,\ ShX\!
Hello, ShX!

2. `pwd` – Print Current Directory

ShX ➜ pwd
/home/user/shx

Redirect Output to File:

ShX ➜ pwd > cwd.txt

3. `cd` – Change Directory

Change to an Absolute Path

ShX ➜ cd /usr/local

Relative Path Navigation

ShX ➜ cd ./bin

Move Up a Directory (`..`)

ShX ➜ cd ..

Go to Home Directory (`~`)

ShX ➜ cd ~

4. `type` – Identify Commands

Check a Built-in Command

ShX ➜ type cd
cd is a shell builtin

Check an External Command

ShX ➜ type ls
ls is /usr/bin/ls

Check an Unknown Command

ShX ➜ type unknowncmd
unknowncmd: not found

5. `exit` – Quit ShX

ShX ➜ exit

✅ Ends the session.

6. Redirection Operators

Standard Output (`>` and `>>`)

Overwrite Output:

ShX ➜ echo "Hello, ShX!" > output.txt

Append Output:

ShX ➜ echo "Appending this line" >> output.txt

Standard Error (`2>` and `2>>`)

Overwrite Errors:

ShX ➜ ls /invalidpath 2> error.log

Append Errors:

ShX ➜ ls /invalidpath 2>> error.log

7. Autocompletion in ShX

Single Tab Completion

If there’s only one match:

ShX ➜ pw<Tab>
ShX ➜ pwd

Double Tab Completion

If multiple matches exist:

ShX ➜ e<Tab><Tab>
echo  exit

External Command Autocompletion

ShX ➜ bas<Tab>
ShX ➜ bash

8. External Command Execution

ShX executes external commands like ls, grep, and mkdir if found in $PATH:

ShX ➜ ls
main.go  shx  README.md

Handling Unknown Commands:

ShX ➜ unknowncmd
unknowncmd: command not found

Future Enhancements

✅ Piping (`|`)

Example: ls | grep main
Allows chaining commands.

✅ Command History

Implementing history to recall past commands.
Storing history in ~/.shx_history.

✅ Job Control

Support for background (bg) and foreground (fg) jobs.
Implementing jobs to list running jobs.
Handling CTRL+Z to stop processes.

ShX is a lightweight yet powerful shell, ideal for learning and customization. Contributions and feature suggestions are always welcome!

Enjoy using ShX and happy coding! 🚀

trajano/ShX