This routine replaces an existing record in the file. It has three parameters: f, record, and size.

F must be a valid file handle returned by S-OPEN-FUNCTION.
Record    points to the new record to place in the file.
Size is the size of the record. It may be zero to indicate the maximum record size for the file. The size of the new record need not match the size of the existing record.

The S-REWRITE-FUNCTION routine does not affect the file position.