{
 In Linux it is possible to duplicate a process with fork. In the original
 process, fork will return the handle to the duplicated process. The
 duplicated process will return zero.
}
program TestFork;
{$APPTYPE CONSOLE}
uses
 SysUtils,
 Libc;
var
 ForkedProcessHandle: __pid_t;
 bForked: Boolean;
procedure ForkNow;
begin
 bForked := true;
 ForkedProcessHandle := fork;
end;
function IsForked: Boolean;
begin
 Result := (ForkedProcessHandle = 0) and bForked;
end;
var
 Lf: Integer;
begin
 sigignore(SIGCHLD);
 bForked := false;
 WriteLn('do some stuff');
 WriteLn('before fork');
 ForkNow;
 WriteLn('after fork - we have dublicated the process');
 if IsForked then begin
  WriteLn('do some stuff in forked process (wait 5s)');
  for Lf := 0 to 50 do begin
  Write('f');
  sleep(100);
  end;
 end else begin
  WriteLn('do stuff in original process (wait 10)');
  for Lf := 0 to 100 do begin
  Write('o');
  sleep(100);
  end;
 end;
 WriteLn;
 if IsForked then
  WriteLn('forked process end')
 else
  WriteLn('original process end');
end.

{
Output of this demo app:
do some stuff
before fork
after fork - we have dublicated the process
after fork - we have dublicated the process
do some stuff in forked process (wait 5s)
fdo stuff in original process (wait 10)
ooffooffooffooffooffooffooffooffooffooffooffooffooffooffooffooffooffooff
ooffooffooffooffooffooffooffoo
forked process end
ooooooooooooooooooooooooooooooooooooooooooooooooo
original process end
}