Hello, World!

This guide walks through compiling a single Kotlin file to every supported target format.

Write the source

Create a file called hello.kt:

fun main() {
    println("Hello, world!")
}

Compile to each target

JVM

skotch emit --target jvm hello.kt -o HelloKt.class
java -cp . HelloKt

Hello, world!

The output is a standard Java 17 class file. You can inspect it with javap -c HelloKt.class if you have the JDK installed.

DEX

skotch emit --target dex hello.kt -o classes.dex

This produces a Dalvik executable suitable for inclusion in an Android APK. You can verify it with dexdump -d classes.dex if you have the Android SDK build-tools.

klib

skotch emit --target klib hello.kt -o hello.klib
unzip -l hello.klib

A klib is a ZIP archive containing serialized IR and metadata. It serves as the intermediate format for the LLVM and native pipelines.

LLVM IR

skotch emit --target llvm hello.kt -o hello.ll
cat hello.ll

Produces about 15 lines of textual LLVM IR. The println call maps to libc puts.

Native binary

skotch emit --target native hello.kt -o hello
./hello

Hello, world!

Note

The native target requires clang on your PATH. Skotch compiles the LLVM IR to an object file and links it in a single clang invocation.

A more interesting example

Create math.kt:

fun factorial(n: Int): Int {
    var result = 1
    for (i in 1..n) {
        result *= i
    }
    return result
}

fun main() {
    for (i in 1..10) {
        println("$i! = ${factorial(i)}")
    }
}

skotch emit --target jvm math.kt -o MathKt.class
java -cp . MathKt

1! = 1
2! = 2
3! = 6
4! = 24
5! = 120
6! = 720
7! = 5040
8! = 40320
9! = 362880
10! = 3628800

This example exercises functions, for loops, mutable variables, compound assignment, and string templates — all features that work across every target.

Project build

For projects with multiple source files, use skotch build instead of skotch emit. Create a project directory:

myapp/
  build.gradle.kts
  src/main/kotlin/
    Main.kt

With a minimal build.gradle.kts:

plugins {
    kotlin("jvm")
    application
}

group = "com.example"
version = "1.0.0"

application {
    mainClass.set("MainKt")
}

Then build and run:

cd myapp
skotch build
java -jar build/example.jar

Next steps

• CLI Reference — All available subcommands and flags
• Language Overview — Supported Kotlin features
• JVM Targets — JAR packaging and Android APKs