How to determine if a scala module is run as script

Question

How do I determine if a Scala module is opened as script or if it is regularly imported?

This question is about the same issue as previous Python question:
how do I determine whether a python script is imported as module or run as script?
but for Scala

I am not sure to understand why there's a negative vote. – paradigmatic Aug 19 '11 at 20:10 — paradigmatic, Aug 19 '11 at 20:10

score 2 · Answer 1 · answered Aug 19 '11 at 16:47

If you just need a quick hack for personal use, you can launch the Scala interpreter with a shell script that also sets an environment variable indicating that the interpreter is running.

Also, keep in mind that there's a difference between Scala and Python that makes the question somewhat moot: In Scala, code expressions can't appear at the top level, unless it's a Scala script. So you'll never really have the ambiguity of writing a Scala script and then wondering if it's being executed some other way.

score 1 · Answer 2 · answered Aug 19 '11 at 21:01

1

All Scala modules are imported regularly, because there is no such thing as opening as a script.

answered Aug 19 '11 at 21:01

Daniel C. Sobral

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score 0 · Answer 3 · answered Aug 19 '11 at 16:41

0

Scala doesn't have the equivalent of Python's __main__ as far as I know so it can't be done in the same way. But I argue you shouldn't be doing this anyway - just write tests for your module or write a script that imports the module.

answered Aug 19 '11 at 16:41

Derek Wyatt

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score 0 · Answer 4 · answered Aug 19 '11 at 20:09

A dirty hack could be to throw and exception and get the trace. You can then examine it to try to guess the context. For example a method like:

def stackTrace: Array[StackTraceElement] =
  try {
    1/0 // cause exception
    Array() //Never executed
  } catch {
    case e: Exception => e.getStackTrace
  }

Will return the full stack trace as an array of StackTraceElement.

However, writing the trace analysis code will be tedious and I don't see any situation where it may be worth of it...

Thanks, I never noticed that method. – paradigmatic Aug 21 '11 at 22:19 — paradigmatic, Aug 21 '11 at 22:19

How to determine if a scala module is run as script

4 Answers4