Jcmdshell (beta-release)

A cross-platform command-line shell built in pure Java, designed around the WORE principle
(Write Once, Run Everywhere).

Note: Jcmdshell is not affiliated with Oracle or the Java® trademark.

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Features

• Works on Windows, Linux, macOS, and Windows on ARM
• Uses JLine for modern terminal input and editing
• Can be built with or without Maven
• Supports both standard JAR and fat JAR builds
• No native dependencies

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Requirements

• JDK 25 or newer
• Maven (optional, but recommended)

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Building with Maven

Maven automatically downloads dependencies and produces two JAR files:

Output	Description
target/Jcmdshell.jar	Standard JAR — requires a lib/ folder with dependencies
target/Jcmdshell-fat.jar	Fat JAR — includes JLine and runs anywhere

Build command:

mvn clean package

clean is optional, but recommended when a target/ directory already exists.

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Building Manually (Without Maven)

1. Download JLine 3.30.6
   https://mvnrepository.com/artifact/org.jline/jline/3.30.6

2. Create a lib/ directory and place the downloaded JAR inside:

mkdir lib

Using a lib/ folder is recommended, but optional if you provide a manifest with the classpath.
The following manual build uses the lib/ setup.

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Manual Compilation

Windows - PowerShell

javac -cp "lib/*" -d target (Get-ChildItem -Recurse -Filter *.java src/main/java/xyz/stackpancakes).FullName

Windows - Batch

dir /B /S "src\main\java\xyz\stackpancakes\*.java" > java_files.txt
javac -cp "lib\*" -d target @java_files.txt
del java_files.txt

*NIX - Shell

javac -cp "lib/*" -d target $(find src/main/java/xyz/stackpancakes -name "*.java")

target/ act as compilation output directories.

On Unix-like systems, a POSIX-compatible sh is assumed to be available.

Running with Nix

If you have Nix installed, you can build and run Jcmdshell without manually managing Java or Maven dependencies:

nix run github:StackPancakes/Jcmdshell

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Packaging a Standard JAR

Your project already includes a MANIFEST.MF with:

Manifest-Version: 1.0
Created-By: StackPancakes
Main-Class: xyz.stackpancakes.Main
Class-Path: lib/jline-3.30.6.jar
Sealed: true
Specification-Title: Jcmdshell
Specification-Version: 0.1.0
Specification-Vendor: StackPancakes
Implementation-Title: Jcmdshell
Implementation-Version: 0.1.0
Implementation-Vendor: StackPancakes

Because of this, creating a new manifest file is optional.
You may reuse the existing one when packaging.

Build the JAR (example places the JAR in target/)

jar cfm target/Jcmdshell.jar MANIFEST.MF -C target .

If your lib/ directory is not next to the JAR, update Class-Path accordingly in your existing MANIFEST.MF.

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Fat JAR (Manual, No Maven)

A fat JAR is created by unpacking dependency JARs and combining their class files with your compiled classes into one runnable JAR.

Do not just place dependency JARs inside your JAR - Java won’t load nested JARs automatically.

1) Compile (same as above)

# PowerShell
javac -cp "lib/*" -d target (Get-ChildItem -Recurse -Filter *.java src/main/java/xyz/stackpancakes).FullName

# *NIX shell
javac -cp "lib/*" -d target $(find src/main/java/xyz/stackpancakes -name "*.java")

2) Create a staging directory

mkdir fatbuild

mkdir -p fatbuild

3) Copy your compiled classes/resources into the staging dir

Copy-Item -Recurse target\* fatbuild\

cp -R target/* fatbuild/

4) Unpack dependencies into the staging dir

Use jar xf inside the staging directory to extract the dependency.

Push-Location fatbuild
jar xf ..\lib\jline-3.30.6.jar
Pop-Location

cd fatbuild && jar xf ../lib/jline-3.30.6.jar

Now fatbuild/ contains:

xyz/stackpancakes/...     # your classes
org/jline/...             # dependency classes
META-INF/...              # manifests, services, signatures from deps

5) Clean META-INF signatures (avoid signature errors)

PowerShell:

Remove-Item fatbuild\META-INF\*.SF -ErrorAction Ignore
Remove-Item fatbuild\META-INF\*.RSA -ErrorAction Ignore
Remove-Item fatbuild\META-INF\*.DSA -ErrorAction Ignore

Batch:

del /Q fatbuild\META-INF\*.SF 2>nul
del /Q fatbuild\META-INF\*.RSA 2>nul
del /Q fatbuild\META-INF\*.DSA 2>nul

*NIX:

rm -f fatbuild/META-INF/*.SF fatbuild/META-INF/*.RSA fatbuild/META-INF/*.DSA

If META-INF/services collisions occur across multiple deps, merge or remove those files as needed.

6) Create a minimal runnable manifest (no Class-Path needed)

Create MANIFEST.MF with:

Manifest-Version: 1.0
Main-Class: xyz.stackpancakes.Main

(Keep the final blank line.)

7) Build the fat JAR from the staging dir

jar cfm target/Jcmdshell-fat.jar MANIFEST.MF -C fatbuild .

8) Run it

Batch / Powershell:

java --enable-native-access=ALL-UNNAMED -jar target\Jcmdshell-fat.jar

*NIX:

java --enable-native-access=ALL-UNNAMED -jar target/Jcmdshell-fat.jar

Notes

• Keep your own META-INF/MANIFEST.MF; do not delete META-INF entirely.
• Remove signature files (*.SF, *.RSA, *.DSA) from unpacked dependencies.
• For many dependencies or complex META-INF/services merges, consider using Maven Shade.

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Running Jcmdshell

Standard JAR (requires lib/ on the classpath)

*NIX:

java --enable-native-access=ALL-UNNAMED -cp "target/Jcmdshell.jar:lib/*" xyz.stackpancakes.Main

Windows:

java --enable-native-access=ALL-UNNAMED -cp "target/Jcmdshell.jar;lib/*" xyz.stackpancakes.Main

Fat JAR (no lib/ required)

java --enable-native-access=ALL-UNNAMED -jar target/Jcmdshell-fat.jar

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Project Structure

Jcmdshell/
 ├─ src/
 │   └─ main/java/xyz/stackpancakes/...
 ├─ lib/                 # only needed for manual builds
 ├─ target/              # Maven outputs .jar here
 ├─ MANIFEST.MF          # used when packaging
 └─ README.md

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Contributing

Pull requests and suggestions are welcome.