It is possible to have whitespace between the
and replaces lines of the form
by the contents of
It is useful if files included with
need to be preprocessed.
should be invoked with the
Note that there must be no whitespace between the leading dot and
the two characters `s’ and `o’. Otherwise, only
even when followed by a character other than space or newline.
The current directory is always searched first.
This option may be specified more than once,
the directories will be searched in the order specified.
No directory search is performed for files specified using an absolute path.