Tinkering with Konstantin's example

KLSigPipeFun.scala

object KLSigPipeFun:
  def main(args: Array[String]) =
    val lines = scala.io.Source.stdin.getLines()
    val lineNumbers = Iterator.from(1)
    val numberedLines = lineNumbers.zip(lines)
    val okLines = numberedLines takeWhile: _ => 
      !scala.sys.process.stdout.checkError()
    val outLines = okLines map:
      case (number, line) => println(s"$number: line")
    println(s"${outLines.length} lines counted")