How to use Kotlin CLI – kotlin, kotlinc, kotlinc-js, kotlin-dce-js

Table of Contents

I write how to use Kotlin CLI, in Kotlin 1.2.41.

Execute Script

Execute script file with kts extension. If the extension is not kts, the command doesn’t execute anything. The error error: source entry is not a Kotlin file is shown.

kotlinc -script sample.kts

1	kotlinc -script sample.kts

sample.kts can be executed if it has no main function.

Sample Code

println("Hello World!")

1	println("Hello World!")

Compile the File

JVM Compilationル

The following command compiles the Kotlin file with extension kt and generates .class file.

kotlinc Sample.kt

1	kotlinc Sample.kt

SampleKt.class will be created.

The following command creates JAR file.

kotlinc Sample.kt -include-runtime -d Sample.jar

1	kotlinc Sample.kt -include-runtime -d Sample.jar

There are 2 ways to execute output Sample.jar file, as follows.

JAR execution 1

kotlinc Sample.jar

1	kotlinc Sample.jar

JAR execution 2

java -jar Sample.jar

1	java -jar Sample.jar

JS Compilation

The following command generates the JavaScript file, sample.js. Map file and meta file are output if you add options.

kotlinc-js Sample.kt -output sample.js

1	kotlinc-js Sample.kt -output sample.js

Kotlin DCE JS

DCE means dead code elimination. It eliminate unused codes in JavaScript. (Reference: https://kotlinlang.org/docs/reference/javascript-dce.html)

For example, create Hello.kt as follows, which has an unused function a.

fun main(vararg args: String) {
println("Kotlin")
}
fun a() {
println(1)
}

fun main(vararg args: String) {

println("Kotlin")

}

fun a() {

println(1)

}

Compile it as follows.

kotlinc-js Hello.kt -output hello.js

1	kotlinc-js Hello.kt -output hello.js

Then, hello.js will be output.

if (typeof kotlin === 'undefined') {
throw new Error("Error loading module 'hello'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'hello'.");
}
var hello = function (_, Kotlin) {
'use strict';
var println = Kotlin.kotlin.io.println_s8jyv4$;
function main(args) {
println('Kotlin');
}
function a() {
println(1);
}
_.main_vqirvp$ = main;
_.a = a;
main([]);
Kotlin.defineModule('hello', _);
return _;
}(typeof hello === 'undefined' ? {} : hello, kotlin);

if (typeof kotlin === 'undefined') {

throw new Error("Error loading module 'hello'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'hello'.");

}

var hello = function (_, Kotlin) {

'use strict';

var println = Kotlin.kotlin.io.println_s8jyv4$;

function main(args) {

println('Kotlin');

}

function a() {

println(1);

}

_.main_vqirvp$ = main;

_.a = a;

main([]);

Kotlin.defineModule('hello', _);

return _;

}(typeof hello === 'undefined' ? {} : hello, kotlin);

Then, execute kotlin-dce-js as follows.

kotlin-dce-js hello.js

1	kotlin-dce-js hello.js

You can use -d option to designate the output directory. Here I don’t use it. Without the option, it outputs hello.js into min directory.

if (typeof kotlin === 'undefined') {
throw new Error("Error loading module 'hello'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'hello'.");
}
var hello = function (_, Kotlin) {
'use strict';
var println = Kotlin.kotlin.io.println_s8jyv4$;
function main(args) {
println('Kotlin');
}
_.main_vqirvp$ = main;
main([]);
return _;
}(typeof hello === 'undefined' ? {} : hello, kotlin);
//# sourceMappingURL=hello.js.map

if (typeof kotlin === 'undefined') {

throw new Error("Error loading module 'hello'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'hello'.");

}

var hello = function (_, Kotlin) {

'use strict';

var println = Kotlin.kotlin.io.println_s8jyv4$;

function main(args) {

println('Kotlin');

}

_.main_vqirvp$ = main;

main([]);

return _;

}(typeof hello === 'undefined' ? {} : hello, kotlin);

//# sourceMappingURL=hello.js.map

The unused function a is successfully deleted.

REPL (Read Eval Print Loop)

We can execute REPL as follows.

kotlinc

kotlinc

To exit the REPL, enter :quit or Ctrl+D.

Help

Execute kotlin, kotlinc, kotlinc-js, kotlin-dce-js commands with the option -h, you can see the help of each command.

The Life