Sometimes, especially with huge log files, you need to delete all the data in a file without getting rid of it. You could just use rm and then touch to re-create the file. The problem is that I inevitably forget to look at the ownerships and and permissions on the file until after I delete it. Instead of rm copy /dev/null to the file instead. This will zero its contents but keep the file and all of its meta data like its permissions and ownerships.
