Using Environment variables to load a file from My Pictures
It’s been a while since I used Environment Variables in Delphi and I had to look it up.
I have a loose rule that anything I have to look up, I want to share on my blog so that I can find it again easily later.
So here you have it: Enviromental Variable expansion ala Delphi.
It’s really not that complex, and it’s possible that this routine could be optimized some. But I think it works well enough as is and demonstrates the use of ExpandEnvironmentStrings quite nicely. If you need to get a list of the variables, you’ll need to do further research on GetEnvironmentStrings and FreeEnvironmentStrings to return the list to you for manipulation. A search for FreeEnvironmentStrings Delphi gives you pleanty of code examples.
Here is my example for ExpandEnvironmentStrings:
-
var
-
ImageFileName, FullFileName: string;
-
BufSize: Integer;
-
NewPath: String;
-
begin
-
// Retrieve the contents of the edit field into a local variable for ease of use.
-
ImageFileName := Edit1.Text;
-
-
// If it exists in the working path, use that as our retrieval point.
-
// Otherwise, look in the Application directory, then the My Pictures folder,
-
// then look in the Windows directory
-
if (FileExists(ImageFileName))
-
then FullFileName := ImageFileName // Working directory needs no path.
-
else if (FileExists(ExtractFilePath(Application.ExeName) + ImageFileName))
-
then FullFileName := ExtractFilePath(Application.ExeName) + ImageFileName // Grab the path from the application executible info
-
else begin
-
-
// Use environmental variables to locate two other possible places
-
// Allow 254 character paths to be returned.
-
SetLength(NewPath, 254);
-
-
// Call ExpandEnvironmentStrings with string containing environmental variables
-
BufSize := ExpandEnvironmentStrings(‘%userprofile%\My Documents\My Pictures\’, PChar(NewPath), 254);
-
-
// The returned BuffSize must be used to truncate off any extra garbage & injections.
-
SetLength(NewPath, BufSize - 1);
-
-
// Look for it and if it is found, assign the full name otherwise keep looking.
-
if (FileExists(NewPath + ImageFileName))
-
then FullFileName := NewPath + ImageFileName
-
else begin
-
// Repeat the above process for the Windows Directory.
-
SetLength(NewPath, 254);
-
BufSize := ExpandEnvironmentStrings(‘%windir%\’, PChar(NewPath), 254);
-
SetLength(NewPath, BufSize - 1);
-
if (FileExists(NewPath + ImageFileName))
-
then FullFileName := NewPath + ImageFileName
-
else FullFileName :=‘NOT FOUND’;
-
end;
-
end;
