Calling CLI tools using kotlin coroutines with cancellation support

cli.kt

import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.cancel
import kotlinx.coroutines.launch
import kotlinx.coroutines.suspendCancellableCoroutine
import java.io.StringWriter

sealed class Cli {
    data class Ok(val stdout: String) : Cli()
    data class Err(val stderr: String) : Cli()
}

suspend fun cli(cmd: String): Cli =
    suspendCancellableCoroutine { cont ->
        val scope = CoroutineScope(cont.context)

        scope.launch(Dispatchers.IO) {
            val process = Runtime.getRuntime().exec(cmd)

            cont.invokeOnCancellation {
                process.destroy()
                scope.cancel()
            }

            val stdout = StringWriter()
            val stderr = StringWriter()

            val ok = launch { process.inputStream.use { it.reader().copyTo(stdout) } }
            val err = launch { process.errorStream.use { it.reader().copyTo(stderr) } }

            val cli = when (process.waitFor()) {
                0 -> {
                    ok.join()
                    Cli.Ok(stdout.toString().trim())
                }
                else -> {
                    err.join()
                    Cli.Err(stderr.toString().trim())
                }
            }

            cont.resume(cli) {
                process.destroy()
                scope.cancel()
            }
        }
    }

suspend fun cli(vararg cmd: String): Cli =
    cli(cmd.joinToString(separator = " "))