Redirect stdout using exec in subscript

Question

I have one main script which is started as an service.

I can't modify this main script, because it is often updated. This main script starts a program, which echo any log to stdout.

So i can't see any log of this program.

But this main script calls at the beginning an hook-script, that I can modify.

If I redirect the stdout to a file in this hook-script, it works for that script, but not for the main script.

Is it possible to change the stdout for the whole process?

main (enigma2.sh):

# hook to execute scripts always before enigma2 start
if [ -x enigma2_pre_start.sh ]; then
  enigma2_pre_start.sh
fi

...

#this logs to stdout
/usr/bin/enigma2

...

hook (enigma2_pre_start.sh)

exec > /tmp/`date +"%s"`.log
exec 2> /tmp/`date +"%s"`_error.log

Edit:

Is it possible, to attach an tee (or similar) to the main process after it is started? I know the main script is only run once. So i can get the process id with ps.

Answer 1

Solution based on the comment from "Zaboj Campula":

if /bin/grep -q "^[[:space:]]/usr/bin/enigma2_pre_start.sh$" /var/bin/enigma2.sh
then
        echo Unpatched > /tmp/enigma.sh
        /bin/sed -e 's/^\t\(\/usr\/bin\/enigma2_pre_start.sh\)$/\t\. \1/g' /var/bin/enigma2.sh -i
        pid=`/bin/ps -o ppid= $$` && /bin/kill $pid
fi

Answer 2

You have to source enigma_pre_start.sh instead of executing it, so that the exec commands run in the same process whose file handles you want to change.

if [ -x enigma2_pre_start.sh ]; then
    . enigma2_pre_start.sh
fi

Otherwise, you are redirecting the standard output and error of the process which executes the hook script, which exits as soon as the script completes.