【列表5.22】項目文件OneInst的內容。
program OneInst;
uses
   QForms,
   SysUtils,
   Libc,
   QDialogs,
   ProcStuff in 'ProcStuff.pas',
   frmOneInst in 'frmOneInst.pas' {OneInstMainForm};
const
  HOME_DIR : PChar = 'HOME';
  BaseLockFileName = '.oneinst. LCK';
 var
  AlreadyRunning : Boolean;
  PID : Integer; { ID for this process }
  ProcStatus : String;
  UserName : String;
  CmdLine : String;
  LockPIDStr : String;
  LockFile : TextFite;
  HomeDirPtr : PChar;
  HomeDirName : String;
  LockFileName : String;
  {SR *.res}
  begin
     AlreadyRunning := False;
     CmdLine := '';
     PID := getpid;
     HomeDirPtr := getenv(HOME_DIR);
HomeDirName := StrPas(HomeDirPtr);
LockFileName := HomeDirName + '/' + BaseLockFileName;

if FileExists(LockFileName)
 then begin
           { Test the file's validity }
           AssignFile(LockFile, LockFileName);
           Reset(LockFile);
           readln(LockFile, LockPIDStr);
           CloseFile(LockFile);
           { Is that original process still running -- and
              is it this application? }
           if GetProcessStatus(StrToInt(LockPIDStr),
                   ProcStatus, UserName, CmdLine)
                 = NO_ERR
             then begin { It exists. Is it a Zombie? }
                      if pos('Z'. ProcStatus) = 0
                       then begin
                                { It's running -- and it's not a Zombie. But
                                   is it *this* application? }
                                 if ExtractFileName(CmdLine) =
                                     ExtractFileName(Application. ExeName)
                                  then begin
                                           AlreadyRunning := True;
                                           MessageDlg('Sorry!', 'Sorry. Only '
                                              + 'one instance of this application '
                                              + 'is permitted to run at a time.'.
                                              mtError, [mbOK], 0);
                                          end;
                                end;
                     end;
           end;
  if not AlreadyRunning
   then begin
             { Create the lock file }
             if FileExists(LockFileName) then DeleteFile(LockFileName):
             AssignFile(LockFile, LockFileName);
             Rewrite(LockFile);
             writeln(LockFile, IntToStr(PID));
             CloseFile(LockFile);
        Application. Initialize;
             Application.CreateForm(TOneInstMainForm, OneInstMainForm);
             Application. Run;
             { Clean up }
             if FileExists(LockFileName) then DeleteFile(LockFileName);
           end;
end.