In my DAQ system, columns represent the channels and each row represent the one scan of the data for all channel. it is easy to get file write by append or overwrite to a exist file. But I sometime want just overwrite new data in last row to a exist file. for example: I have DAQ with 10 channels and scan all channel for three times in each run. So my data file will be 10 columns and 3 rows in each run if I set "append" file. next time I want record the data by "overwrite" (so just one row in 3 scans) in the same file but just overwrite in 11th row (so I will keep all the data I previousely got). How can do this?

Hi GPIB Analyzer. why do you need to read the whole file? You can:- get the file size with "Get file size" or "file/directory info"- set the read position with "Set file position" You should subtract 1024 from file size, set this as file position, read 1024 bytes. Now analyze this 1kb of data, find the last row, set file position again, write to file. No need to read the whole file. And as noted before:How should Labview know the last line in the file without searching for it? You can do this search better than a simple brute force attack

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how to write to a existing file but overwrite data just in last row

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Thanks GerdW,

I sovled this problem, even through it is not so simple. But your point out is very helpful in my answer!

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how to write to a existing file but overwrite data just in last row

Re: how to write to a existing file but overwrite data just in last row