Hmmm... I'm not sure there's any general
way to determine that, without ennumerating and testing
for specific systems. Why do you need to know? Do the
tests have an adverse effect if they're unnecessary? Are
they run often enough to impact performance? What happens on a single-user system (e.g., BeOS, MacOS 9, or DOS), that you want to avoid?
Also, how are you defining "single-user system"?
Does Windows 98 count, even though it has a concept
of user accounts? Why? Because only one can be active
at a time, or because the filesystem doesn't have
a concept of file ownership? Which? If the latter,
would a Linux system count if the files in question
are on a vfat or UMSDOS filesystem?
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