xcall MIAMEX, MX_PRFSPEC, string

MX_PRFSPEC retrieves the last processed file specification and formats it in standard AMOS format (i.e. dev#:file.ext[p,pn]) where dev# and [p,pn] are omitted if the file is on the current device or in the current directory.

As a practical matter, the last processed filespec will be the one last processed via MX_FSPEC.