Perl string parsing code

Question

I was wondering if someone could help me better understand what this given code to parse a text file is doing.

  while ($line = <STDIN>) {
    @flds = split("\t", $line);
    foreach $fld (@flds) {
        if ($fld =~ s/^"(.*)"$/\1/) {
            $fld =~ s/""/"/g;
        }
    }
    print join("\t", @flds), "\n";
}

We are given this block of code as a start to parse a text file such as.

Name    Problem #1  Comments for P1 E.C. Problem    Comments    Email
Park, John  17  Really bad. 5       [email protected]
Doe, Jane   100 Well done!  0   Why didn't you do this? [email protected]
Smith, Bob  0       0       [email protected]

...which will be used to set up a formatted output based on the parsed text.

I'm having trouble fully understanding how the block of code is parsing and holding the information so that I can know how to access certain parts of the information I want. Could someone better explain what the above code is doing at each step?

Trenton Trama · Accepted Answer · 2013-06-26 00:15:45Z

1

This is actually looks kind of a really crappy way to parse a CSV file.

while ($line = <STDIN>) { #read from STDIN 1 line at a time.
    @flds = split("\t", $line);  #Split the line into an array using the tab character and assign to @flds
    foreach $fld (@flds) {  #Loop through each item/column that's in the array @fld and assign the value to $fld
        if ($fld =~ s/^"(.*)"$/\1/) {  #Does the column have a string that is surrounded in quotes?  If it does,  replace it with the string only.
            $fld =~ s/""/"/g; #Replace any strings that are only two double quotes.
        }
    }
    print join("\t", @flds), "\n";  #Join the string back together using the tab character and print it out.  Append a line break at the end.
}

answered Jun 26, 2013 at 0:15

Trenton Trama

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2 Comments

Yoink Over a year ago

Thank you, so this block of code isn't doing much more than changing a bit of the formatting of the text and rejoining it back together with tab separated values correct?

doubleDown Over a year ago

Better if you put the explanation outside the code instead of commenting inside the code

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