====== Writing an Environment Variable ======

The function to write an environment variable is [[https://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/setenvironmentvariable.asp|SetEnvironmentVariable()]].  The code below will create an environment variable called DataPath, representing the path to the application's data.  The function will set it to C:\Data\.  Paste the code below in the [[CLICK_event|CLICK Event]] of a button in a window:

<code>
declare function SetEnvironmentVariable

key = 'DataPath'

value = 'C:\Data\'

rv = SetEnvironmentVariable ( key , value)
</code>
 

The values of the key and value are, of course, known before the call, so there is no need to predetermine the buffer size.  Only one call is necessary.

=== The Windows API Declaration ===

The code above will not run until the declaration for [[https://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/setenvironmentvariable.asp|SetEnvironmentVariable()]] has been added.  To add the declarations, do the following:


  * Log out of the application.
  * Log into the SYSPROG application.
  * Add a row, (call it DLL_APICALLS_KERNEL32), with the first line as KERNEL32 and containing the declarations as shown below.

<code>
KERNEL32
LONG STDCALL SetEnvironmentVariableA(LPCHAR, LPCHAR) As SetEnvironmentVariable
//....add any other declarations in KERNEL32 here.....
</code>

The function is aliased to its the ANSI version SetEnvironmentVariableA().

  * Save  the row.
  * Run [[declare_FCNS|Declare_FCNS]] at the System Editor Exec Line to create the declaration header, as shown below:

RUN DECLARE_FCNS 'DLL_APICALLS_KERNEL32'

  * Exit the editor.
  * Log out of SYSPROG.
  * Log into your application.
  * Run the window.