#/bin/bash
batch.sh --user=stefano --option=read-only --password=my_password_very_secret
batch.sh --password=password --user=dummy --option=abc
batch.sh --option=abc --user=dummy2 --password=whatever
batch.sh --user=dummy3 --password=12345

Script: batch.sh

#!/bin/bash
# do something > /path/to/log/file.txt
echo "$@" | tr ' ' 'n' | sed 's|password=(.*)|password=********|' | tr 'n' ' ' >> /path/to/log/file.txt
echo "completed" >> /path/to/log/file.txt