Thread: Code to search a file and take out a column

Sure it's possible.

You read the input file line by line, and extract each column , and immediately write that to it's corresponding output file. Loop until the end of the input file.

This sounds like a job for a scripting language though. I wouldn't do this in C++ unless it was part of a larger program.

Sure it's possible.

Try say
fin >> a >> b >> c;

Then
f1 << a;

etc

That's what while loops are for.

A lot of the "what's best/easiest" depends on EXACTLY what the format is. If the file is simply something like this:

Code:

1 2 3
4 5 6

then using the method described by Salem will be the simples (and perfectly adequate as long as you don't need to care about "idiot entered rubbish into the file" or "file got destroyed by attempt to copy it that failed"etc) method.

If you have a file that contains "extra decorations" (e.g. quotes or commas), then you will need to come up with a more advanced method of reading the data, as you need to somehow deal with those "decorations" - the method described by Salem won't work DIRECTLY, but if you know the format, and deal with it appropriately, it can be solved by a method SIMILAR to Salems - again with the provision that if you need to deal with error conditions, it gets a bit harder (handling errors ALWAYS adds more work than just doing the stuff that doesn't deal with errors - in fact, more of the code I write deal with "if(error)..." than the code that actualy does "real work").

--
Mats

Code:

<?php
$filename = "path/to/file";
$ext = ".csv"
$infile = fopen($filename.$ext,"r");
$line = fgetcsv($infile);
$outpufiles=array();
while($line)
{
    $i=0;
    foreach(array_values($line) as $cell)
    {
        $i++;
        if(!$outputfiles[$i])
        {
            $outfiles[$i] = fopen($filename."col".$i.$ext,"a");
        }
        fwrite($outfiles[$i],cell);
    }
    $line = getcsv($infile);
}
foreach(array_values($outfiles) as $file)
{
    fclose($file);
}
?>

the above is an example in PHP. whatever tool you decide to use, the algorithm will be something similar to the above.

Your PHP code needs some work. You are calling fopen over every single iteration of the output loop. That means you will open each output file "n" times where "n" is number of rows of output. That's a bit too much.

In addition, you are only parsing one line of the input CSV file.

Do you even need to write a program for this!
If this is just for a one-off, you can just import it into Excel and then copy-n-paste the columns out into other files. (if you have access to Excel)
Or you could just attach the file to your post here and I'll split it for you.