78 files declare their use of FileSystemInterface

ArchiverManager.php in core/lib/Drupal/Core/Archiver/ArchiverManager.php
AssetDumper.php in core/lib/Drupal/Core/Asset/AssetDumper.php
color.module in core/modules/color/color.module
Allows users to change the color scheme of themes.
ConfigController.php in core/modules/config/src/Controller/ConfigController.php
ConfigExportUITest.php in core/modules/config/tests/src/Functional/ConfigExportUITest.php
ConfigImportForm.php in core/modules/config/src/Form/ConfigImportForm.php
CopyTest.php in core/modules/file/tests/src/Kernel/CopyTest.php
CssCollectionOptimizer.php in core/lib/Drupal/Core/Asset/CssCollectionOptimizer.php
DirectoryTest.php in core/tests/Drupal/KernelTests/Core/File/DirectoryTest.php
Download.php in core/modules/migrate/src/Plugin/migrate/process/Download.php
DownloadTest.php in core/modules/file/tests/src/Functional/DownloadTest.php
EnvironmentCleaner.php in core/lib/Drupal/Core/Test/EnvironmentCleaner.php
ExportForm.php in core/modules/locale/src/Form/ExportForm.php
file.inc in core/includes/file.inc
API for handling file uploads and server file management.
file.module in core/modules/file/file.module
Defines a "managed_file" Form API field and a "file" field for Field module.
FileCopy.php in core/modules/migrate/src/Plugin/migrate/process/FileCopy.php
FileCopyTest.php in core/modules/migrate/tests/src/Unit/process/FileCopyTest.php
FileCopyTest.php in core/tests/Drupal/KernelTests/Core/File/FileCopyTest.php
FileItem.php in core/modules/file/src/Plugin/Field/FieldType/FileItem.php
FileMoveTest.php in core/tests/Drupal/KernelTests/Core/File/FileMoveTest.php
FileMoveTest.php in core/modules/image/tests/src/Functional/FileMoveTest.php
FileProcessBase.php in core/modules/migrate/src/Plugin/migrate/process/FileProcessBase.php
FileSaveDataTest.php in core/tests/Drupal/KernelTests/Core/File/FileSaveDataTest.php
FileStorage.php in core/lib/Drupal/Core/Config/FileStorage.php
FileSystemForm.php in core/modules/system/src/Form/FileSystemForm.php
FileSystemTest.php in core/tests/Drupal/KernelTests/Core/File/FileSystemTest.php
FileTestForm.php in core/modules/file/tests/file_test/src/Form/FileTestForm.php
FileTestSaveUploadFromForm.php in core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
FileTranslation.php in core/lib/Drupal/Core/StringTranslation/Translator/FileTranslation.php
FileUploadForm.php in core/modules/media_library/src/Form/FileUploadForm.php
FileUploadResource.php in core/modules/file/src/Plugin/rest/resource/FileUploadResource.php
FileUrlTest.php in core/modules/file/tests/src/Kernel/FileUrlTest.php
FunctionalTestSetupTrait.php in core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
GDToolkit.php in core/modules/system/src/Plugin/ImageToolkit/GDToolkit.php
HtaccessDeprecationTest.php in core/tests/Drupal/KernelTests/Core/File/HtaccessDeprecationTest.php
image.install in core/modules/image/image.install
Install, update and uninstall functions for the image module.
image.module in core/modules/image/image.module
Exposes global functionality for creating image styles.
Image.php in core/modules/media/src/Plugin/media/Source/Image.php
ImageDimensionsTest.php in core/modules/image/tests/src/Functional/ImageDimensionsTest.php
ImageFieldDefaultImagesTest.php in core/modules/image/tests/src/Functional/ImageFieldDefaultImagesTest.php
ImageItem.php in core/modules/image/src/Plugin/Field/FieldType/ImageItem.php
ImageStyle.php in core/modules/image/src/Entity/ImageStyle.php
ImageStylesPathAndUrlTest.php in core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
ImageTest.php in core/tests/Drupal/Tests/Core/Image/ImageTest.php
ImageThemeFunctionTest.php in core/modules/image/tests/src/Kernel/ImageThemeFunctionTest.php
install.core.inc in core/includes/install.core.inc
API functions for installing Drupal.
install.inc in core/includes/install.inc
API functions for installing modules and themes.
InstallHelper.php in core/profiles/demo_umami/modules/demo_umami_content/src/InstallHelper.php
JsCollectionOptimizer.php in core/lib/Drupal/Core/Asset/JsCollectionOptimizer.php
KernelTestBase.php in core/modules/simpletest/src/KernelTestBase.php
Local.php in core/lib/Drupal/Core/FileTransfer/Local.php
locale.batch.inc in core/modules/locale/locale.batch.inc
Batch process to check the availability of remote or local po files.
locale.install in core/modules/locale/locale.install
Install, update, and uninstall functions for the Locale module.
locale.module in core/modules/locale/locale.module
Enables the translation of the user interface to languages other than English.
LocaleExportTest.php in core/modules/locale/tests/src/Functional/LocaleExportTest.php
LocaleImportFunctionalTest.php in core/modules/locale/tests/src/Functional/LocaleImportFunctionalTest.php
LocaleUpdateBase.php in core/modules/locale/tests/src/Functional/LocaleUpdateBase.php
MailTest.php in core/modules/system/tests/src/Kernel/Mail/MailTest.php
media.install in core/modules/media/media.install
Install, uninstall and update hooks for Media module.
MoveTest.php in core/modules/file/tests/src/Kernel/MoveTest.php
OEmbed.php in core/modules/media/src/Plugin/media/Source/OEmbed.php
QuickEditImageController.php in core/modules/image/src/Controller/QuickEditImageController.php
SaveDataTest.php in core/modules/file/tests/src/Kernel/SaveDataTest.php
SaveUploadFormTest.php in core/modules/file/tests/src/Functional/SaveUploadFormTest.php
SaveUploadTest.php in core/modules/file/tests/src/Functional/SaveUploadTest.php
simpletest.module in core/modules/simpletest/simpletest.module
Provides testing functionality.
SimpletestPhpunitRunCommandTest.php in core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
SiteSettingsForm.php in core/lib/Drupal/Core/Installer/Form/SiteSettingsForm.php
StreamWrapperTest.php in core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php
system.install in core/modules/system/system.install
Install, update and uninstall functions for the system module.
system.module in core/modules/system/system.module
Configuration system that lets administrators modify the workings of the site.
TemporaryJsonapiFileFieldUploader.php in core/modules/jsonapi/src/Controller/TemporaryJsonapiFileFieldUploader.php
TestBase.php in core/modules/simpletest/src/TestBase.php
ThemeSettingsForm.php in core/modules/system/src/Form/ThemeSettingsForm.php
ToolkitGdTest.php in core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php
update.manager.inc in core/modules/update/update.manager.inc
Administrative screens and processing functions of the Update Manager module.
UpdateManagerInstall.php in core/modules/update/src/Form/UpdateManagerInstall.php
UpdatePathTestBase.php in core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php

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