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fileptr(lun [, offset] [, /start, /eof, /advance])
fileptr, lun [, offset] [, /start, /eof, /advance]
Show or set a file pointer. fileptr,lun shows and
fileptr(lun) returns the position of the file pointer of
logical unit lun in bytes from the start of the file. If
offset and/or a keyword are specified, then the file
pointer is modified. If a keyword is specified but not
offset, then zero is taken for offset. You
can move a file pointer beyond the end of a file, but not before the
beginning of the file. If you read data from beyond the end of a file,
or from a dataless gap in a file, then zeros are returned.
/startcounts from the start of the file.
/eofcounts from the end-of-file marker (which is one byte beyond the last byte in the file).
/advancecounts from the current position.
If no keyword is defined, then non-negative offset counts
from the start and negative offset from the end-of-file
marker (with -1 pointing at the last byte of the file). The
function version returns 1 on success, 0 or failure.