How to add increasing number to saved files in Delphi?

I'm making a program that takes a snapshot of the screen, and saves it to a folder as a Bitmap picture. I seem to be running into a problem though, the picture just overwrites itself.

Can anyone tell me how I can make it so when it saves, the number will be one higher than the last? For example: Save 1: Screenshot0001.bmp Save 2: Screenshot0002.bmp Save 3: Screenshot0003.bmp

And so on.

From stackoverflow

• At program startup, iterate all Screenshot*.bmp files, parse out the numeric part and find the highest - assign this value to your counter. When doing a snapshot, go into a loop that tries crreating Screenshot.bmp with "only create if doesn't exist already" (CREATE_NEW) semantics, incrementing the counter until you find an unused name.

  Alternately, use timestamp instead of counter :)

  mghie : +1 for the tip to do this atomically (multi-user friendly). But given the experience level of the OP the other answer seems to be more appropriate.

• There are many ways to accomplish something like this.

  1. Do it like your digital camera does; Have a counter and save it in a file or in the registry. You'll probably run into multi-user problems and you'll still have to handle situations where an image already exists.

  2. Don't use a incrementing number, but write a datetime in the filename. FileName := 'Screenshot_'+FormatDateTime('yyyymmdd-hhnnss-zzz.bmp',now());

  3. Do something like the code below to find the latest number. I think this does what you're describing, but remember that this code will get slower as you write more images. With thousands of pictures and a slow drive or network it could 'hang' your program.

  ..

  i := 0;
  while FileExists(Format('%sScreenshot%.04d.bmp',[ImgPath,i])) do
    inc(i);
  

  PuppyKevin : I'm having a problem. I added FileName := +FormatDateTime('yyyymmdd-hhnnss-zzz.bmp',now()); and added [FileName] to the following code: bmp.SaveToFile('C:\Screenshots\ScreenShot[FileName].bmp'); But I don't know if I am doing it right. The FileName:= says that it is undeclared.

  Rob Kennedy : You need to declare your variables, Kevin. Check the help about that. Also check the help about string concatenation.

  PuppyKevin : I declared the FileName variable as FileName: string;, I re-wrote the FileName := and SaveTo lines as: FileName := 'Screenshot_'+FormatDateTime('yyyymmdd-hhnnss-zzz',now()); bmp.SaveToFile('C:\Screenshots\[FileName].bmp');, and now, when it makes and saves the Bitmap, it comes out as [FileName].bmp.

  mghie : @PuppyKevin: Try "bmp.SaveToFile('C:\Screenshots\' + FileName + '.bmp');" instead, or use another Format() call: "bmp.SaveToFile(Format('C:\Screenshots\%s.bmp', [FileName]));"

  PuppyKevin : mghie, I used your Format() way, and it worked! Thank you everyone for helping me out :)

• You need a routine like this which mimics Windows file duplication where the first file is 'My File', the second is 'My File (2)', then 'My File (3)' etc.

  function AppendDuplicationNumber( const AStr : string ) : string;
  // Used to make strings unique
  // This examines the string AStr for trailing '(n)' where
  // 'n' is an integer.
  // If the (n) part is found, n is incremented, otherwise '(2)' is
  // appended to the string.
  var
    iLH, iRH, I : integer;
    S           : string;
  begin
    Result := AStr;
    iLH    := CharPosBackwards( '(', Result );
    If iLH > 0 then
      begin
      iRH := PosEx( ')', Result, iLH );
      If iRH > 0 then
        begin
        I := StrToIntDef( Copy( Result, iLH+1, iRH-iLH-1 ), 0 );
        If I > 0 then
          begin
          Inc(I);
          S := IntToStr( I );
          Delete( Result, iLH+1, iRH-iLH-1 );
          Insert( S, Result, iLH+1 );
          Exit;
          end;
        end;
      end;
  
    // Did not increment existing (n), so append it.
    Result := Result + ' (2)';
  end;
  

  mghie : This is clearly not what the OP intended, he specifically wants file names with one part being an increasing number.