Deleting Information From A Log File

I am parsing a log file and want to delete all the information from a certain point forward in the file. I believe this to be a simple process, but the solution is eluding me today. I thought that I would be able to retrieve all the characters from the right somehow, to the point where I wish to delete the rest of the data, and then run another funtion to delete, but can't seem to work it out.

Any guidance is appreciated.
Thanks.