currentRecord = rec(fileID)
This function returns the record number of the record where the "file mark" is currently located, in the open file specified by
fileID. The first record in the file is considered Record #0.
To calculate the record number,
rec uses the record length that was specified in the
open statement when the file was opened. If no record length was specified, a default length of 256 bytes is used. If you specified a record length of "1" when you opened the file,
rec returns the file mark's byte position within the file.
To determine the file mark's offset from the beginning of the record, use the
record; loc; open