Print output from process launched from groovy

Question

In a groovy script I start an external process with:

def proc = command.execute()
proc.consumeProcessOutput( System.out, System.err )
proc.waitFor()
println "\nDone. Exit value: ${proc.exitValue()}"

But how do I write the output from the application if it fails?

There is:

  proc.errorStream
  proc.outputStream

But maybe the output is automatically written when using the consumeProcessOutput method?

Answer 1

If you pass System.out and System.err to consumeProcessOutput(), the output and error streams will both printed out automatically. If you want to capture it, pass in your own output steams:

def out = new ByteArrayOutputStream()
def err = new ByteArrayOutputStream()
def proc = command.execute()
proc.consumeProcessOutput(out, err)
proc.waitFor()

println "error stream was ${err.toString()}"

Answer 2

To avoid ‘running-forever’ process (this happens on some Windows env when output exceeds 4096 bytes) add initial size to ByteArrayOutputStream

def initialSize = 4096
def out = new ByteArrayOutputStream(initialSize)
def err = new ByteArrayOutputStream(initialSize)
def proc = command.execute()
proc.consumeProcessOutput(out, err)
proc.waitFor()