This permits the existence of directory hierarchies, i.e., directories containing sub-directories. Most computers organize files into hierarchies using folders, directories, or catalogs. Each archive can contain multiple directories and files. Some search engines also mine data available in databases or open directories. Samba sets up network shares for chosen Unix directories (including all contained subdirectories). The following are both directories and search engines. Multiple files in different directories may have the same name. Time Machine creates multiple hard links to unmodified directories. Storage devices use directories (or folders) as namespaces. To users, they appear as normal directories or files. There are symbolic links relating most of the usual Unix directories to the GoboLinux tree. The macOS APIs support listing, getting, setting, and removing extended attributes from files or directories. Zotero also does not offer automatic generation and updating of bibliography files in select directories. A command that provides accelerated access to frequently-used files and directories. Examples of well-known general web directories are Yahoo!