Merlin's Delphi Forge

You want to save data to a temporary file but you don’t what to file name to use? Well, this function does all the work for you.

function CreateUniqueFileName(sPath: string): string;
var
  chTemp: Char;
begin
  repeat
    Randomize;
    repeat
      chTemp := Chr(Random(43) + 47);
      if Length(Result) = 8 then
        Result := Result + '.'
      else if chTemp in ['0'..'9', 'A'..'Z'] then
        Result := Result + chTemp;
    until Length(Result) = 12;
  until not FileExists(sPath + Result);
end;

This is the harder way to print text in Delphi If you want to do it the easier way check out tip 4.1. Well, if for some reasons you may want to print using the Windows API here’s the code:

Code 1:

uses
  Printers, WinSpool;
...
var
  aDriver, aPort, aPrinterName: array[0..255] of Char; { aDriver and aPort won't be used }
  iSize, iN: Integer;
  Info: PAddJobInfo1;
  fPrinter: TextFile;
  hPrinter: THandle;
begin
  Printer.GetPrinter(aPrinterName, aDriver, aPort, hPrinter);
  OpenPrinter(aPrinterName, hPrinter, nil);
  try
    AddJob(hPrinter, 1, nil, 0, iSize); { Get buffer size }
    GetMem(Info, iSize);
    try
      { This function will return the name of the file we can write to }
      AddJob(hPrinter, 1, Info, iSize, iN);
      { Now write to the file }
      AssignFile(fPrinter, Info^.Path);
      Rewrite(fPrinter);
      try
        WriteLn(fPrinter, 'Hello world!');
        WriteLn(fPrinter, 'This is text will be printed...');
      finally
        CloseFile(fPrinter);
      end;
      { Put the file into the printing line, after that Windows will delete it }
      ScheduleJob(hPrinter, Info^.JobId);
    finally
      FreeMem(Info);
    end;
  finally
    ClosePrinter(hPrinter);
  end;
end;

Code 2:

{ Will work only if the printer is on LPT1 (almost always:-) }
...
LPTHandle := CreateFile('LPT1', GENERIC_WRITE, 0, PSecurityAttributes(nil),
OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
...

Then use WriteFile() to send text or:

...
while not TransmitCommChar(LPTHandle, CharToSend) do
  Application.ProcessMessages;

(* This code will send characters to the printer waiting for each one of them
** to be taken care of.
*)