FTELL(stream)

The result of this function is the current file pointer associated with
the given stream (with 1 meaning the beginning), that can be used as a
position parameter to the charin or charout calls.  If that could not
be determined (for example, the stream is a pipe or is not open) then -1
will be returned.

NOTE: This is the actual file pointer, not the read or write pointer as
      stored by REXX (though the answer will probably equal one of those,
      according as to whether the last operation on the stream was a read
      or a write).

This call is equivalent to STREAM(stream,'c','ftell') and may be
deleted in future releases.