The external “real” filename is stored in file.name. It is initialized when creating a new file. If none is specified, a temporary file with a random name will be created.
var/savefile/F1
var/savefile/F2
F1 = new() // create a temp file
F2 = new("myfile") // open "myfile"
world << "F1.name = [F1]"
world << "F2.name = [F2]"