abstract class CustomTask extends DefaultTask {
                @InputFile
                @PathSensitive(PathSensitivity.NONE)
                abstract RegularFileProperty getSource()

                @OutputFile
                abstract RegularFileProperty getTarget()

                @TaskAction
                def execute() {
                    target.get().asFile.text = source.get().asFile.text
                }

package gradlebuild.docs;

import org.gradle.api.DefaultTask;
import org.gradle.api.GradleException;
import org.gradle.api.UncheckedIOException;
import org.gradle.api.file.DirectoryProperty;
import org.gradle.api.file.RegularFileProperty;
import org.gradle.api.tasks.CacheableTask;
import org.gradle.api.tasks.InputDirectory;
import org.gradle.api.tasks.OutputFile;
import org.gradle.api.tasks.PathSensitive;
import org.gradle.api.tasks.PathSensitivity;

import org.gradle.api.file.Directory;
import org.gradle.api.file.DirectoryProperty;
import org.gradle.api.file.FileCollection;
import org.gradle.api.file.RegularFile;
import org.gradle.api.file.RegularFileProperty;
import org.gradle.api.problems.Severity;
import org.gradle.api.problems.internal.GradleCoreProblemGroup;
import org.gradle.api.tasks.Input;
import org.gradle.api.tasks.Optional;

            abstract class MyApplicationJvmArguments implements CommandLineArgumentProvider {
                @InputFile
                @PathSensitive(PathSensitivity.NONE)
                abstract RegularFileProperty getInputFile()

                @Override
                Iterable<String> asArguments() {
                    return ["-Dinput.file=\${inputFile.get().asFile.absolutePath}".toString()]
                }

            // 3) consumer's input is wired to producer's output

            abstract class ProducerTask extends DefaultTask {

                @OutputFile
                abstract RegularFileProperty getProducerOutput()

                @TaskAction
                void doAction() {
                    throw new VerificationException("ProducerTask threw VerificationException")
                }
            }

 */

package org.gradle.api.tasks;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import org.gradle.api.DefaultTask;
import org.gradle.api.file.RegularFileProperty;
import org.gradle.api.internal.file.FileOperations;
import org.gradle.internal.IoActions;
import org.gradle.internal.UncheckedException;
import org.gradle.internal.deprecation.DeprecationLogger;

You can learn more about `RegularFileProperty` and `DirectoryProperty` in <<lazy_configuration#lazy_configuration,Lazy Configuration>>.
====

                @SkipWhenEmpty @IgnoreEmptyDirectories
                @InputFiles
                abstract ConfigurableFileCollection getSources()

                @OutputFile
                abstract RegularFileProperty getOutputFile()

                @TaskAction
                void doStuff() {
                    println("Running...")
                    outputFile.get().asFile.text = "executed"
                }

        where:
        propertyType          | options               | optionValue | methodName          | description
        'RegularFileProperty' | ['--myProp=test.txt'] | 'test.txt'  | 'fileProperty'      | 'provided'
        'RegularFileProperty' | []                    | 'null'      | 'fileProperty'      | 'not provided'
        'DirectoryProperty'   | ['--myProp=testDir']  | 'testDir'   | 'directoryProperty' | 'provided'

     * By default, the original type is determined from the lazy property type, e.g.:
     * Property[T] -> original type becomes T (also Property[Integer] -> Integer and not int)
     * RegularFileProperty -> original type becomes File
     * DirectoryProperty -> original type becomes File
     * MapProperty[K, V] -> original type becomes Map[K, V]
     * ListProperty[T] -> original type becomes List[T]