I am trying to make a Windows batch file (the main script) redirect all of it's output to a file while still displaying it on the screen. I cannot change all the code that calls the main script - I need to change the main script itself.

I have a solution that requires "bootstrapping" the main script by calling it again from another bat file (tee_start.bat). What I'm sure I want to avoid is refactoring all the other scripts that call main.bat to use the tee command - it will be a much smaller, safer change if I can put some new code in main.bat.

Is there a way to do this that does not involve restarting the main file as I am doing below? For example, is there a cmd.exe or powershell.exe command that says "Take my current STDOUT and tee it" - or does tee somehow support this behavior and I missed it? Or, alternatively, should I settle for what I have implemented as the least invasive method?

I have implemented a solution as follows:

main.bat

REM this is an example of bootstrap mode - it will restart this main script with all output logged
call tee_start.bat %~dpnx0 %*

echo This output should appear both in the screen console and in a log file

tee_start.bat

REM in order to bootstrap the output redirection - this script gets called twice - once to initialize logging with powershell tee command
REM second time, it just echoes log information and returns without doing anything
if x%LOG_FILE% neq x (
    echo Bootstrapped Process: %1%
    echo Escaped Arguments: