External monitor won't write to file when run

what are the permissions on the file, who owns it, and which directory is it in? Bear in mind, when you run the script you are probably effectively running it as root. When bigd runs the monitor, it's running as itself. I would make sure the file you want to write to is somewhere like /shared/tmp/ and that the file is owned by bigd and retest. Make sure bigd has write access, also.