Rundll32

The Run DLL utility (Rundll32.exe) included in Windows enables you to call functions exported from a 32-bit DLL. These functions must have the following syntax:


Note that EntryPoint is a placeholder for the actual function name. For a list of possible show states, see WinMain.

The following is the command-line syntax for Rundll32:


DllName
Specifies the name of the DLL. The name cannot contain spaces, commas, or quotation marks. The utility searches for the DLL using the search criteria documented for the LoadLibrary function. Therefore, it is best to use the short name and provide a full path for the DLL.
FunctionName
Specifies the name of the function to call in DllName. Requires a comma (without no spaces) between DllName and FunctionName.
Arguments
Optional arguments for FunctionName.
Rundll32 loads the specified DLL using LoadLibrary, obtains the address of the function using the GetProcAddress function, and calls the function with the specified arguments, if any. When the function returns, Rundll32 unloads the DLL and exits.

It is possible to create a Unicode version of the function. Rundll32 first tries to find a function namedEntryPointW. If it cannot find this function, it tries EntryPointA, then EntryPoint. To create a DLL that supports ANSI on Windows Me/98/95 and Unicode otherwise, export two functions: EntryPointW and EntryPoint.