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Searching for Existing Applications, Files, Registry Entries or .ini File Entries

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Windows Installer can search for a specific file or directory during an installation. File or directory searches are used to determine whether a user has already installed a version of an application.

AppSearch Action searches a user system for file signatures that are specified in the AppSearch Table. If the AppSearch action finds an installed file or directory with the specified signature, it sets a corresponding property, also specified in the AppSearch Table, to the ___location of the file or directory. When searching for a file, the file signature must also be listed in the Signature Table. If a file signature is listed in the AppSearch Table and is not listed in the Signature Table, the search looks for a directory, registry entry, or .ini file entry.

To expedite the search of a user computer, the Installer queries the following locator database tables in the order listed for a suggested search ___location:

  • If the file signature is listed in the CompLocator Table, the suggested search ___location is the key path of a component. If the signature is not listed in this table or not installed at the suggested ___location, the Installer queries the RegLocator Table for a suggested ___location.
  • If the file signature is listed in the RegLocator Table, the suggested search ___location is a key path written in the user registry. If the signature is not listed in this table or not installed at the suggested ___location, the Installer queries the IniLocator Table for a suggested ___location.
  • If the file signature is listed in the IniLocator Table, the suggested search ___location is a key path written in an .ini file present in the default Windows directory of a user system. If the signature is not listed in this table or not installed at the suggested ___location, the Installer queries the DrLocator Table for a suggested ___location.
  • If the file signature is listed in the DrLocator Table, the suggested search ___location is a path in the user directory tree. The depth of subdirectory levels to search below this ___location is also specified in this table.

The first time the Installer finds the file signature at a suggested ___location, it stops searching for this file or directory, and sets the corresponding property in the AppSearch Table. For more information, see the following: