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15.5.219 fileptr

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.


counts from the start of the file.


counts from the end-of-file marker (which is one byte beyond the last byte in the file).


counts 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.

See also: openr, openw, openu