mark

mark is a compiled Lisp function in `simple.el'.

(mark &optional FORCE)

Return this buffer's mark value as integer, or nil if never set.

In Transient Mark mode, this function signals an error if
the mark is not active. However, if `mark-even-if-inactive' is non-nil,
or the argument FORCE is non-nil, it disregards whether the mark
is active, and returns an integer or nil in the usual way.

If you are using this in an editing command, you are most likely making
a mistake; see the documentation of `set-mark'.