I'd guess that rob_au is correct about importing the constants. Read flock to see how to import the constants.

As for the garbage in the file.. there's one thing that I see that could be causing it. When you read in the data, where's the file pointer? You then truncate the file. I'm not positive, but I think your pointer is beyond the end of the file.

Before you truncate it, do a

seek FH, 0, 0;
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I did a quick test and without the seek, I couldn't see anything in the file. When I used seek, everything printed fine.

Hope this helps..
Rich