Difference between file and URL

[John Rule]

I am discovering that open/write/close to a file can be a problem if the
original file size is larger than the new data size...it simply overwrites
data in the file, leaving the extra data in tact. Using 'put into URL' does
not do this (it overwrites the entire file). Is this correct behavior, or a
bug?

(2.5 engine)

JR