procedure ExtractTemporaryFile(const FileName: String);

Extracts the specified file from the [Files] section to a temporary directory. To find the location of the temporary directory, use ExpandConstant('{tmp}').

The extracted files are automatically deleted when Setup exits.

An exception will be raised if the file wasn't extracted successfully, if the file wasn't found, or if the file was found but couldn't be processed because of its MinVersion and/or OnlyBelowVersion parameters.

Use Flags: dontcopy in the [Files] section to tell Setup to skip the file during the normal file copying stage.

Use Flags: noencryption in the [Files] section if encryption is enabled and you call the ExtractTemporaryFile function prior to the user entering the correct password.

When solid compression is enabled, be sure to list your temporary files at (or near) the top of the [Files] section. In order to extract an arbitrary file in a solid-compressed installation, Setup must first decompress all prior files (to a temporary buffer in memory). This can result in a substantial delay if a number of other files are listed above the specified file in the [Files] section.

[Files]
Source: "Readme.txt"; Flags: dontcopy noencryption

[Code]
function InitializeSetup: Boolean;
var
  S: AnsiString;
begin
  // Show the contents of Readme.txt (non Unicode) in a message box
  ExtractTemporaryFile('Readme.txt');
  if LoadStringFromFile(ExpandConstant('{tmp}\Readme.txt'), S) then
  begin
    MsgBox(S, mbInformation, MB_OK);
  end;

  Result := True;
end;

ExtractTemporaryFiles