Javascript - How to read a file while it is written

Question

So say there's a log file, or in my case, a binary data file. (I'm pulling data to chart real-time stripcharts.) I'd like to read it all in and do whatever, and then have my FileReader trigger again once the local file has been updated. Is this functionality supported?

Edit If I understand this correctly, then this isn't possible. Once done, the file is no longer being read. Say it ain't so! Any ways to continue reading from that point?

@jbabey Not true. html5rocks.com/en/tutorials/file/dndfiles

savinger
– savinger

2013-01-21 16:34:25 +00:00
Commented Jan 21, 2013 at 16:34 — savinger
– savinger, Commented Jan 21, 2013 at 16:34

George · Accepted Answer · 2013-01-21 16:41:09Z

1

Section 8 of the File API spec specifies that File objects should have a lastDateModified property. You could check this field at a regular interval and if it has changed, reread the file. As you already found in the spec, it is unfortunately not possible to continue reading from where you left off.

answered Jan 21, 2013 at 16:41

George

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2 Comments

savinger Over a year ago

Thanks for the input. What is your understanding of slice? Can I slice before reading? So that only a certain portion is read?

George Over a year ago

@savinger, I haven't used the File API extensively, but I'm confident that Blob.slice() is used to slice out chunks of data after the Blob has been read.

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