Here's another option as a couple people suggested on the gnuplot list, but
unfortunately I'm not sure it is portable... only of use in unix based
systems:
stuff an "rm" at the end of the plot command so that gnuplot removes the
file
afterward:
Actually, that is a great point---it is certainly true on Unix, but I
think also on Windows and Mac: when a program opens a disk file, the
OS holds the disk metadata. At that point, the file might be deleted
from the filesystem, but the program will still be able to access it,
including reading/writing/appending. Only after the file is closed
will the data and metadata be released and the file will be gone for
good.