Create unique file name Windows batch

Question

I have seen many posts about creating a unique filename from the naive %TIME% to the plausible (but insufficient) %RANDOM%. Using wmic os get localdatetime is m

Answer 1

At first some remarks for using a PID as a part of a unique file name:

When you just look for a parent PID this might be ambiguous because when you run that code in a for loop or in a call within your batch file always a new cmd.exe is created and you get the PID of this temporary cmd.exe process.

So you should rather use the PID of your batch "root" cmd.exe process. In order to get that - instead of searching by title in the the task list, which is slow and might also be ambiguous, there is another approach.

You can get the PID of your batch "root" cmd.exe process by using Windows API functions:

• GetConsoleWindow provides the console window handle
• GetWindowThreadProcessId provides the PID by using this console window handle

You can run these Windows API functions by using PowerShell:

Add-Type -MemberDefinition @"
  // HWND WINAPI GetConsoleWindow(void)
  [DllImport("kernel32.dll", EntryPoint = "GetConsoleWindow")]
  public static extern IntPtr GetConsoleWindow();

  // DWORD GetWindowThreadProcessId(HWND hWnd, LPDWORD lpdwProcessId)
  [DllImport("user32.dll", EntryPoint = "GetWindowThreadProcessId")]
  public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

  public static uint GetPID()
  {
    IntPtr h = GetConsoleWindow();
    if ((uint)h==0) return 0;
    uint rc = 0;
    GetWindowThreadProcessId(h, out rc);
    return rc;
  }
"@ -Name Win32 -NameSpace System

[System.Win32]::GetPID();

Within your batch file you can run the PowerShell code as an encoded command:

set MyPID=
for /f %%a in ('powershell -NoLogo -NoProfile -NonInteractive -EncodedCommand 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^=^= 2^>nul') do (
  set "MyPID=%%~a"
)

if defined MyPID echo %MyPID%