relativeTo

Calculates the relative path for this path from a base path.

fun Path.relativeTo(base: Path): Path(source)

import java.nio.file.Paths
import kotlin.io.path.relativeTo

fun main() {
    val base = Paths.get("/home/user/docs")
    val file = Paths.get("/home/user/docs/project/readme.md")

    val relative = file.relativeTo(base)
    println(relative) // outputs: project/readme.md
}

Source