from twisted.internet import utils, reactor def printTrueValue(val): print "/bin/true exits with rc=%d" % val output = utils.getProcessValue('/bin/false') output.addCallback(printFalseValue) def printFalseValue(val): print "/bin/false exits with rc=%d" % val reactor.stop() output = utils.getProcessValue('/bin/true') output.addCallback(printTrueValue) reactor.run()