in reply to Parsing CSV only returns the second line of the file

Hello saint_geser, and welcome to the Monastery!

In addition to the modulus problem highlighted by Anonymous Monk, above (and ignoring the fact that the code snippet you gave doesn’t compile!), there is a problem with the following line:

open (TEMP, '>', $temp) or die Lava::Message("Can't open temporary fil
+e");

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This occurs within the outer while loop, so on each iteration, whenever the if condition succeeds, the temp file is truncated (“clobbered,” erased) as it is re-opened for output. See open.

Move the open statement to before the loop, so it is executed only once.

Hope that helps,

Athanasius <°(((>< contra mundum

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Re^2: Parsing CSV only returns the second line of the file
by saint_geser (Initiate) on Sep 01, 2012 at 09:54 UTC

    Thanks guys for your replies! I'm still quite confused. This is my first perl script and I haven't done any programming since uni.

    The reason it wouldn't compile (works fine for me) is because I have perl as a part of proprietary mining software which has their own extension modules installed, e.g. Lava. I don't get any errors or warnings when running it.

    The part of code that does the parsing I got from somewhere on the internet and modified for my purpose and I'm not quite sure where the inner while cycle is from. I'm pretty sure it shouldn't be there.

    So I've commented out the inner cycle and moved the part where I open TEMP file for editing and insert two lines up the top out of the outer cycle. Now this part of code looks like this: 

            while ( <OLD> )
            {
                next if ($. == 1);
                    if ($csv->parse($_))
                    {
                        my @columns = $csv->fields();

                # print the parsed body of old file

                        print TEMP "$columns[0], $columns[2], $columns
+[1], $columns[3], $columns[0]\n";

#while( <OLD> )
#{
#print TEMP $_;
#last if $. % 1;
#}

                        }
                        else
                        {
                        my $err = $csv->error_input;
                        Lava::Message("Failed to parse line: $err");
                        }
               }

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    The output that I get now has only the top 2 and bottom 2 lines:

    W1582165 ,01-Sep-12,,Dist=Metres
0, 0.000, 0.000, 0.000, 0.000, 0.000, 0.000
0, 0.000, 0.000, 0.000,
0, 0.000, 0.000, 0.000, END

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    I still can't figure out how to make parsing work properly. I'm actually very confused about this line:

    next if ($. == 1);

    It says next if line number equals to 2? In the example that I saw it parsed the whole file but here does it just parse the second line?

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      The reason it wouldn't compile (works fine for me) is because I have perl as a part of proprietary mining software which has their own extension modules installed, e.g. Lava. I don't get any errors or warnings when running it.

      Then what you posted isn’t exactly what you’re running, since this line in the original post (fixed in the new post, I see):

      if ($csv->parse($_)

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      is missing a closing parenthesis, and the final line:

      END;

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      should be __END__.

      It says next if line number equals to 2?

      No, array elements start counting at zero, but line numbers begin at one. So that statement says: Skip the first line of data. (Presumably, the original code expected the first line to be a heading?)

      You are making progress, but it’s difficult to say why your code is failing without a complete, self-contained script. Also, detailing the output you expect/desire would help the monks know what you are trying to achieve. Please see How do I post a question effectively?.

      Update: Minor edit.

      Athanasius <°(((>< contra mundum

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