Java Mini Shell (POSIX Compliant) 🐚

This project is a custom implementation of a POSIX-compliant shell written in Java. It is capable of handling standard shell tasks, including running built-in commands, executing external programs, and managing input/output redirection and pipelines.

✨ Features

The shell provides core functionality necessary for interacting with the operating system:

Built-in Commands

The following essential shell commands are implemented natively in Java:

• exit [status]: Exits the shell, optionally with a specified status code.
• echo [args]: Prints arguments to standard output.
• type [command]: Identifies how a command would be interpreted (as a builtin, or as an external program found in the PATH).
• pwd: Prints the name of the current working directory.
• cd [path]: Changes the current working directory, supporting absolute paths and the home directory (~) shortcut.

Core Functionality

• External Command Execution: Searches the system's PATH to find and execute external programs (e.g., ls, grep).
• Command Pipelines: Supports chaining commands using the pipe operator (|), routing the standard output of one command to the standard input of the next.
• I/O Redirection: Supports redirecting or appending standard output (>, >>, 1>, 1>>) and standard error (2>, 2>>) to a specified file.

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🛠️ Prerequisites

To build and run this project, you need the following tools installed on your system:

• Java Development Kit (JDK) 25 or higher: The project is configured to use the Java 25 language level and preview features.
• Apache Maven: Used to manage dependencies and build the executable JAR file.

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🚀 Getting Started

1. Build the Executable

Execute the Maven package goal from the root directory. This command compiles the code and bundles it into a single executable file named mini-shell.jar (based on previous steps to rename the artifact).

mvn -B package

2. Run the Shell

The final executable file will be located at target/mini-shell.jar.

Once the build is complete, you can start the shell using the Java executable. Note the mandatory --enable-preview flag to run the code compiled with modern Java features.

java --enable-preview -jar target/mini-shell.jar

3. Usage Example

$ echo "Hello World"
Hello World
$ type echo
echo is a shell builtin
$ pwd
/home/user/my-mini-shell
$cd src/main/java$ pwd
/home/user/my-mini-shell/src/main/java
$ cat Main.java | grep "import"
import java.util.*;
import java.io.*;