Keeping two processes alive in bash script (and respawning them when dead)

I used to have the following lines in my script in order to keep alive my process:

while [ -f $FILENAME ]
do
    echo "Running $BINNAME"
    ./$BINNAME >> $LOGNAME
    sleep 1
done

Which worked fine for me. But my problem comes when I try to achieve the same behavior but calling two processes. In other words, In need my script to launch both of them and, constantly check if they fall. If so, launching again the fallen process.

There is no possibility to use pgrep or systemd.

What would you suggest me?

I tried the following:

while [[ -f $FILENAME && -f $FILENAMEPROC ]]
do
    echo "Running $BINNAME + $BINNAMEPROC"
    ./$BINNAME >> $LOGNAME
    ./$BINNAMEPROC >> $LOGNAMEPROC
    sleep 1
done

But obviously, the script waits BINNAME to finish, then launches BINNAMEPROC. And this is not valid because I need both processes to be running simultaneosly.

Launching both on background with & and then using ps | grep [name] is also not valid because it could cause false possitives if someone adds a new process containing the string name.

You can run your two while loops in parallel like this:

while : ; do
   echo 1 running
   sleep 3
done &

while : ; do
   echo 2 running
   sleep 3
done

The ampersand (&) after done puts the first loop into the background, thereby allowing the second loop to proceed in parallel.