loads the given preference file, and sets the current preferences accordingly.
If the optional filename argument is not specified, the file
requester is opened, and you are prompted to select a file. (You can
inhibit the file requester opening by using the
command; see NoFileReq.) If you escape from the file requester, you
can input the file name on the command line.
Note that a preferences file is just a macro containing only option modifiers. You can manually edit a preferences file for special purposes, such as filtering out specific settings. See Hints and Tricks.