Waiting for parallel batch scripts

Question

I have 4 batch files. I want to run one.bat and two.bat at once, concurrently. After completion of these two batch files, three.bat an

Answer 1

This is easily done using a much simplified version of a solution I provided for Parallel execution of shell processes. Refer to that solution for an explanation of how the file locking works.

@echo off
setlocal
set "lock=%temp%\wait%random%.lock"

:: Launch one and two asynchronously, with stream 9 redirected to a lock file.
:: The lock file will remain locked until the script ends.
start "" cmd /c 9>"%lock%1" one.bat
start "" cmd /c 9>"%lock%2" two.bat

:Wait for both scripts to finish (wait until lock files are no longer locked)
1>nul 2>nul ping /n 2 ::1
for %%N in (1 2) do (
  ( rem
  ) 9>"%lock%%%N" || goto :Wait
) 2>nul

::delete the lock files
del "%lock%*"

:: Launch three and four asynchronously
start "" cmd /c three.bat
start "" cmd /c four.bat