How to invoke external command from within Kotlin code?

Question

I want to invoke an external command from Kotlin code. In C/Perl, I would use system() function. In Python, I would use the subprocess module. In Go, I would us

Answer 1

As this is the first google result when searching for how to run commands in kotlin, I found my self struggeling to extend it to get basic standard input working, as the Pipe "|" is not supported for the ProcessBuilder. I've found out how to do it, and thought I'd share. I've converted jkschneider's answer to be run as a simple function, now with optional stdin and output capturing. It's a little less pretty, but more flexible. You can run it like this:

exec("someCommandWithUserInput", stdIn = "yes")

/** Run a system-level command.
 * Note: This is a system independent java exec (e.g. | doesn't work). For shell: prefix with "bash -c"
 * Inputting the string in stdIn (if any), and returning stdout and stderr as a string. */
fun exec(cmd: String, stdIn: String = "", captureOutput:Boolean = false, workingDir: File = File(".")): String? {
    try {
        val process = ProcessBuilder(*cmd.split("\\s".toRegex()).toTypedArray())
            .directory(workingDir)
            .redirectOutput(if (captureOutput) ProcessBuilder.Redirect.PIPE else ProcessBuilder.Redirect.INHERIT)
            .redirectError(if (captureOutput) ProcessBuilder.Redirect.PIPE else ProcessBuilder.Redirect.INHERIT)
            .start().apply {
                if (stdIn != "") {
                    outputStream.bufferedWriter().apply {
                        write(stdIn)
                        flush()
                        close()
                    }
                }
                waitFor(60, TimeUnit.SECONDS)
            }
        if (captureOutput) {
            return process.inputStream.bufferedReader().readText()
        }
    } catch (e: IOException) {
        e.printStackTrace()
    }
    return null
}