Re: Bareword "SEEK_END" not allowed while "strict subs" in use (truncate)

Your use of truncate() doesn't make sense in context.

As noted in the comment, seek( FH, 0, SEEK_END ) will seek to the end of the file. But truncate( FH, 0 ) will then truncate the file to size 0. This means your seek position will now be past the end of the file (unless the file had already been empty). This means that when you next write to the file, nil bytes will be used to fill the first part of the file up to the point of your seek position.

I could see a point of opening the file in a manner that doesn't truncate for the explicit purpose of only truncating the file after you have obtained a lock. In such a case, I don't see how seeking to the end of the file would make sense.

I could also see the point of seeking (perhaps by reading) to a point in the file and then truncating from that point on before writing. In such a case, you would not pass 0 as the 2nd argument to truncate(). And that only makes sense if the seek point might not be the current end of the file.

I hope that helps to clarify things for you.

See also truncate,2.

- tye

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Re^2: Bareword "SEEK_END" not allowed while "strict subs" in use (truncate) by thanos1983 (Parson) on May 09, 2014 at 15:30 UTC
To: tye, Ok, starting to make more sense. My plan was to use flock() to lock the file while my process will be either reading or writting to it. I want to avoid 2 processes together reading and writting simultaneously which will result on overlaping. So my plan was to lock the file seek to the end of the file so I can write the next part of my output, close the file and allow the next process to write on it. I was under the impression that I have to use truncate to empty the rest of the file at the end, to make sure there is nothing left besfore start writting. I got this idea from the tutorial File Locking where they use both: `seek(MYFILE, 0, 0); truncate(MYFILE, 0);` [download] This is my part of confusion.	[reply] [d/l]

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Re^2: Bareword "SEEK_END" not allowed while "strict subs" in use (truncate)
by thanos1983 (Parson) on May 09, 2014 at 15:30 UTC

To: tye,

Ok, starting to make more sense.

My plan was to use flock() to lock the file while my process will be either reading or writting to it. I want to avoid 2 processes together reading and writting simultaneously which will result on overlaping.

So my plan was to lock the file seek to the end of the file so I can write the next part of my output, close the file and allow the next process to write on it.

I was under the impression that I have to use truncate to empty the rest of the file at the end, to make sure there is nothing left besfore start writting.

I got this idea from the tutorial File Locking where they use both:

seek(MYFILE, 0, 0);
truncate(MYFILE, 0);
[download]

This is my part of confusion.

[reply]
[d/l]