Ammonite Shell - Environment Output Odd Behaviour

environment-out.scala

/*
 * Simple script to show / work out why environment variables are not passing through
 * in some circumstances
 *
 * run this on a suitable "*nix" box like 'ARG=foobar amm environment-out.scala'
 */
import ammonite.ops._
import ammonite.ops.ImplicitWd._

def main() = {

  // here is out environment variable
  println("----------- " + sys.env("ARG"))

  // these work
  %(root/'bin/'bash, "-c", "echo '=========== '$ARG",ARG=sys.env("ARG"))
  %(root/'bin/'bash, "-c", "echo ........... $ARG", ARG=sys.env("ARG"))

  // remove (and ignore if not there)
  %%(root/'bin/'rm, "debug-output.sh")
  // create a simple "output dumper"
  write(cwd/"debug-output.sh", "#!/bin/sh\necho $*\necho environment : ARG=$ARG\n")

  %(root/'bin/'chmod, "755", "debug-output.sh")

  // these don't
  %(cwd/"debug-output.sh", "::::::::::: $ARG", ARG=sys.env("ARG"))

  %(cwd/"debug-output.sh", "~~~~~~~~~~~ ", "$ARG", ARG=sys.env("ARG"))

  // the right way to do it

  val someString = "this is my ARG=${ARG} string"
  val varRegex = """(\$\{(\w+)\})""".r

  val expanded = varRegex.replaceAllIn(someString,a => s"${sys.env(a.group(2))}")

  %(cwd/"debug-output.sh", "√√√√√√√√√√√ ", expanded)


}

example-running.md

this is the example output from running the above scala script with ARG=foobar amm environment-out.scala

----------- foobar
=========== foobar
........... foobar
::::::::::: $ARG
environment : ARG=foobar
~~~~~~~~~~~ $ARG
environment : ARG=foobar
√√√√√√√√√√√ this is my ARG=foobar string
environment : ARG=foobar