PLEAC: Process Management and Communication (Scala)

gistfile1.scala

/* Process Management and Communication
 * see http://pleac.sourceforge.net/pleac_perl/processmanagementetc.html
 * Scala 2.9.1
 */

import scala.sys.process._
import scala.io.Source
import java.io.File

/* Gathering Output From a Program */

val output = "program args" !!                // collect output into one multiline string
val output = ("program args" !!).split("\n")  // collect output into array, one line per element

var output = ""
Process("program args").lines.foreach { line =>
  output += line
}

val output = Process("program args").lines.foldLeft("") { (out, line) => out + line }

val output = Process("program args").lines.foldLeft("")(_+_)

var output = ""
val p = Process(List("program", "arg1", "arg2"))
val pio = new ProcessIO(stdin => (),
                        stdout => Source.fromInputStream(stdout).getLines.foreach { line => output += line },
                        stderr => Source.fromInputStream(stderr).getLines.foreach(println))
p.run(pio)

/* Running Another Program */

val file = "test.txt"
val status = "vi " + file !<      // not without terminal issues on exit

val file = new File("test.txt")
List("ls", "-l") ### "echo -n" ### "echo -n" #> file !

val infile = new File("infile.txt")
val outfile = new File("outfile.txt")
"cat" #< infile #> outfile !     // no obvious way to include stderr in the mix

(List("program", "arg1", "arg2") !) == 0 || sys.exit(-1)       // jvm exits with code -1
(List("program", "arg1", "arg2") !) == 0 || sys.error("fail")  // jvm raises runtime exception

import sun.misc.{Signal, SignalHandler}  // there is no completely portable signal management in java/scala

val signo = ("program arg1 arg2" !) & 127
if (signo != 0) {
  sys.error("program killed by signal " + signo)
}

Signal.handle(
  new Signal("INT"),
  new SignalHandler {
    override def handle(signal: Signal) = println("Tsk tsk, no process interruptus")
  }
)