Quick question: How to save strings to a file?

[Big_man]

Hello,

I want to save strings to a .txt file. I can't use wirte to measurement file as string doesn't have timestamp.

I tried to use "wirte to text file", but it seems that it only saves the last value. If I build an array of strings using build array and shift register, everytime I stop and run the vi again, the string array will not be cleared, all new data will be appended to old data. 

I'm wondering that is there any solutions? The string format is 111,222   333,444.

Thank you so much and have a good thanksgiving!

[P@Anand]

If you are using the low level primitive, try to use the "Set File Position" function before using the "Write to File" primitive.

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If I build an array of strings using build array and shift register, everytime I stop and run the vi again, the string array will not be cleared, all new data will be appended to old data. 

Are you initializing the Shift register?

[Bob_Schor]

You don't show us any code (so we can't tell what you've tried, nor what version of LabVIEW you are using), but if you look at the Help for the function called (in my Version) "Write to Text File", and read the Detailed Help, you should learn (a) how to be sure you are appending to the end of a file that already has data, and (b) how to do "incremental" writes, that is, write a line as you get it (without having to accumulate all of the lines in an array).  Note that I'm assuming you are generating the data a line at a time -- you can easily "have your cake and eat it, too", that is, accumulate an array of "all the lines" yet still write only the latest line (just do the Write before doing the "append to array").

Bob Schor

[Big_man]

Hi Bob,

Sorry I forgot to attach my code.

I just want to read data from serial port, and save strings to a text file constantly.

[Big_man]

Thank you P@Anand,

Could you please take a look on my code that attached previously?

Write to text file function only saves the latest value.

[Bob_Schor · Accepted solution]

The snippet below shows the logic of the code you posted, which I called "Write One Line".  If you followed my suggestion to look at the Help for Write to Text File, you would have seen the following:  "If you wire a path, the function opens or creates the file before writing to it and replaces any previous file contents".

This is exactly what you are seeing, so the function is behaving "as advertised".  However, it goes on to say "If you wire a file refnum to the file input, writing begins at the current file position".  This is the behavior that you want.  So try this model instead (which I call "Write Many Lines":

You open the file once, before the While loop where you generate "many lines" and write each one, one at a time, to the Text File, closing the file when you exit the loop.  Give that a try (and next time, try to figure things out yourself by carefully reading the Help documents, looking at the Examples suggested at the end of the Help document, etc.).

Bob Schor

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[PalanivelThiruvenkadam]

Use File Operations properly Open/(Read/Write)/Close. while opening the file make sure you are providing correct option for operation.