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How to POST Form Data Using Ruby

Thu, Apr 24, 2008

Automation, Code, Ruby, Scraping

POSTing data on web forms is essential for writing tools and services that interact with resources already available on the web. You can grab information from your Gmail account, add a new thread to a forum from your own app, etc.

The following is a brief example on how this can be done in Ruby using Net::HTTPand this POST form example.

Looking at the source (interlacken.com/webdbdev/ch05/formpost.asp):

<form method="POST" action="formpost.asp">
<p><input type="text" name="box1″ size="20″ value="">
<input type="submit" value="Submit" name="button1″></p>
</form>

We see two attributes are sent to the formpost.asp script when the user hits the submit button: A textbox named box1 and the value of the submit button, named Submit. If this form used a GET method, we would just fetch the URL postfixed with (for example) ?box1=our+text+here. Fortunately, Ruby’s Net::HTTP makes posting data just as easy.

The Ruby code:

#!/usr/bin/ruby

require "uri"
require "net/http"

params = {'box1′ => 'Nothing is less important than which fork you use. Etiquette is the science of living. It embraces everything. It is ethics. It is honor. -Emily Post',
'button1′ => 'Submit'
}
x = Net::HTTP.post_form(URI.parse('http://www.interlacken.com/webdbdev/ch05/formpost.asp'), params)
puts x.body

# Uncomment this if you want output in a file
# File.open('out.htm', 'w') { |f| f.write x.body }

Sending the value of button1 is optional in this case, but sometimes this value is checked in the server side script. One example is when the coder wants to find out if the form has been submitted – as opposed to it being the user’s first visit to the form – without creating a hidden attribute to send along w/ the other form fields. Besides, there’s no harm in sending a few more bytes.

If you’re curious about URI.parse, it simply makes the URI easier to work with by separating and classifying each of its attributes, effectively letting the methods in Net::HTTP do their sole job only, instead of having to analyze and parse the URL. More info on this in the Ruby doc.

Assuming no errors, running this example (ruby postpost or chmod a+x postpost.rb; ./postpost.rb) yields:

<form method="POST" action="formpost.asp">
<p><input type="text" name="box1″ size="20″ value="NOTHING IS LESS
IMPORTANT THAN WHICH FORK YOU USE. ETIQUETTE IS THE
SCIENCE OF LIVING. IT EMBRACES EVERYTHING. IT IS ETHICS.
IT IS HONOR. -EMILY POST">
<input type="submit" value="Submit" name="button1″></p>
</form>

In practice, you might want to use a more specialized library to handle what you’re doing. Be sure to check out Mechanize and Rest-client.

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3 Comments For This Post

  1. Adam Says:

    Thanks for the tutorial. I was looking for a tutorial on parsing data using Ruby only. Majority of the stuff on the web only discuss about the Rails. Thanks for sharing!

    Adam’s last blog post..Mother’s Day Eve

  2. Bill Says:

    Thanks for the quick overview. Needed this today and was having a mental block on how it could work. As usual, very simple with Ruby. Thanks!

  3. moutaman Says:

    Thanx it’s very nice tutorial, i liked it. it works for me.

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