Darkspell: Regular expressions for HTML form elements: 2

According to the text

Gadgets

Authentication

Crypto

ENV

HTTP

Regex

Regex 2

Robots

Snarfs

SSL

Stepper

Text fields are the most prevalent in the usual form, and relatively easy to handle, so let's start there. A text input boxe can be easily identified by the string ≶input type="text" ... It's tempting to write a simple regex that recognizes the field name and stuffs the data into a value parameter to this tag.

$val = $query->param($key);
$html_content =~ s/(<input type="?text"? name="?$key"?)/$1 value="$val"/si;

What's good about this code? Using /si it matches across line breaks, and it's case-insensitive. Also, using ? makes the quote marks optional. It will match <input type="TEXT" name="First_name" size="25">, but it won't match <input name="First_name" type="TEXT" size="25">

You COULD require that all HTML form tags MUST have the type parameter first, immediately followed by the name parameter. But that's too easy, and besides, it's prone to breaking. What if you (or another maintainer) later edit the HTML? If you're not familiar with the code, or have forgotten about it, you may spend the better part of an hour discovering why it's broken.

Much better to make the code flexible and robust. Start by pulling only the text fields out of the parameter list. How? Not by a regex alone. Use Perl's split function to get at each <input individually.

# make an array to store the fields
my @t = ();

my @text_fields = split(/<input /i, $html_content);

# process all but the first fragment
for (1..@texts_fields -1) {

# test for the text parameter

if ($text_fields[$_] =~ /type="?text/i &&

$text_fields[$_] =~ /name="?([\-\w]*)"?/i) {

# isolate the name tag w/ parentheses

# and push it onto your array

push(@t, $1);

}
}

You split the whole file into parts, each -- except the first -- beginning with an <input tag. Somewhere in that tag is a name field. If there's also a text type field, grab the name by parenthesizing it and back-referencing it.

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