Re: point_lun question

[Wayne Landsman <landsman(at)mpb.gsfc.nasa.gov>]

Frank wrote:

> Hi,
> I have a data file with several measurements separated by some header
> lines followed by data points. The whole file containes many
> measurements. So I want to write a procedure, that reads the header and
> the position of the file pointer at the end of the header and returns
> this in a structure for further data processing.
> Actually the routine finds the header, however, point_lun returns the
> 'correct' value only for the first header. If I check the second
> position of the pointer using an hexditor the positions are not correct.
> Whats wrong ? Do I use the wrong data type
>

Are you running under Windows?   If so, then you may need to add a /BINARY
(or /NOAUTOMODE) switch to your openr statement.-- otherwise your use of
the EOF() function can corrupt the file pointer.       It has something to
do with whether   the file is being read in text mode or binary mode, as
discussed in the Windows-specific documentation for openr.   (However, the
way that the EOF() function can corrupt the file pointer without these
keywords present still feels like a bug to me.)

Peter Mason wrote a note on this problem to comp.lang.idl-pvwave last
March.

--Wayne
Landsman
landsman@mpb.gsfc.nasa.gov