GenerateSomeDsl.mwe2

module org.eclipse.xtext.example.arithmetics.GenerateArithmetics

import org.eclipse.xtext.xtext.generator.*
import org.eclipse.xtext.xtext.generator.model.project.*

var rootPath = ".."

var sublimePath 
/*
 * Some more stuff in between
 */
		language = StandardLanguage {
			name = "org.eclipse.xtext.example.arithmetics.Arithmetics"
			fileExtensions = "calc"

			serializer = {
				generateStub = false
			}
			validator = {
				// composedCheck = "org.eclipse.xtext.validation.NamesAreUniqueValidator"
			}
			fragment = WriteToExternalFolderFragment {
				absolutePath = sublimePath
//				override = true
			}
		}

WriteToExternalFolderFragment.xtend

import com.google.inject.Injector
import org.eclipse.xtend.lib.annotations.Accessors
import org.eclipse.xtext.xtext.generator.AbstractXtextGeneratorFragment
import org.eclipse.xtext.xtext.generator.model.IXtextGeneratorFileSystemAccess
import org.eclipse.xtext.xtext.generator.model.XtextGeneratorFileSystemAccess
import org.eclipse.emf.mwe2.runtime.Mandatory

class WriteToExternalFolderFragment extends AbstractXtextGeneratorFragment {
	
	String absolutePath
	
	@Accessors(PROTECTED_GETTER, PUBLIC_SETTER)
	boolean ^override = false
	
	IXtextGeneratorFileSystemAccess outputLocation
	
	override generate() {
	  // content is produced here
	  // Currently processed Grammar is obtained via getGrammar
		outputLocation.generateFile('MyFileName.txt', 'SomeContent')
	}
	
	protected def getOutputLocation() {
		return outputLocation
	}
	
	override initialize(Injector injector) {
		super.initialize(injector)
		this.outputLocation = new XtextGeneratorFileSystemAccess(absolutePath, override)
		injector.injectMembers(outputLocation)
	}
	
	protected def getAbsolutePath() {
		return absolutePath
	}
	
	@Mandatory
	def void setAbsolutePath(String absolutePath) {
		this.absolutePath = absolutePath
	}
	
}