Symbolic links question

[martin at noscvax.UUCP]

    Given the command 'ln -s foo foo.sl', which creates a symbolic link
to an arbitrary file foo,
Is there any documentation on which commands operate on foo, and which
operate on foo.sl?
Commands such as ls, mv, and rm operate on foo.sl, whereas commands
like cat, cp, and grep, given foo.sl as an argument, operate on foo.
That is, 'mv foo.sl foo2' results in foo2 having the type 'symbolic link',
whereas 'cp foo.sl foo2' makes foo2 a duplicate of foo.
How can I determine, other than trial-and-error which commands use foo.sl and which
use foo?
Doug Martin
martin at nosc