Is there a way to change records in a Datalog file

[hfettig]

Here is what I want to do:

I have 240 records (cluster of data), which I want to randomly access and modify.

The accessing part is easy but every time I try to change one of the records a new record is added to the end of the file. I do set the file position before calling the write function, but I just noticed in the help for the write function that it says that the file pointer is always set to the end of the file before writing.

Is there a way to avoid that or will I have to go with my own custom binary format?

Cheers,

Heiko

[jdunham]

QUOTE (hfettig @ Jan 26 2009, 08:41 AM)

I have 240 records (cluster of data), which I want to randomly access and modify.

The accessing part is easy but every time I try to change one of the records a new record is added to the end of the file. I do set the file position before calling the write function, but I just noticed in the help for the write function that it says that the file pointer is always set to the end of the file before writing.

Is there a way to avoid that or will I have to go with my own custom binary format?

I think the datalog format is just a cluster of two elements: a DBL timestamp (old-fashioned) and a cluster of all the front panel data in tab order. I don't know if there's also a header at the beginning of the file. It shouldn't be too hard to read all the records, modify the one you want, and write everything back to a new file.

That being said, the datalog format is a terrible format, and I really wish they would revamp that system, since the datalog feature is really great. You might be better off with your own format or TDMS format.

[hfettig]

Thanks, I went with a custom binary format. Works well now.