RedirectedScriptOutput.groovy

// Bind 'out' variable to redirect script printing methods.
out = new StringWriter()

// Child script inherits our bindings, including 'out'.
// def result = evaluate(new File('TargetScript.groovy'))
def result = evaluate '''
    def a = 42
    println "The answer is $a."
    a ** 2
'''

def output = out.toString()

// Re-redirect 'out'.
// 'out = null' would also work in this case since System.out is the default.
out = System.out

println "Result: $result"
println "---"
print output
println "---"

// If you have many print calls and you're a speed freak then
// setting 'out' to a PrintWriter is a little faster:
//      out = new PrintWriter(new StringWriter())
// Then because Groovy lets us be cavalier about member access
// we can get to the StringWriter without an extra variable:
//      def output = out.out.toString()