The linux way to tail a file is simple. Use this command on your log file as soon as the logging process starts:
tail -f log_file_name.log >> /tmp/new_file_name.log &
[EDIT] tail -f log_file_name.log >> /tmp/new_file_name.log | tail -f /tmp/new_file_name.log | xargs -I TailOutput echo sed -i '/TailOutput/d' log_file_name.log
Then you can use this new_file_name.log to do whatever you want to do with this new file. Also your original log file is intact. I understand this is getting little twisted, but that's the way I can think now!!!