If you're a Vonage user and you'd like to keep tabs on your bill as the month progresses, the script described here can help. The script uses curl to login to your Vonage account and download the web page with your current balance. The balance is then extracted using grep and sed.

Downloading web pages with curl is fairly easy, it gets a bit tricky though when you need to login to a web site before you can get to the web page you want to download. The basic sequence of steps to get to a page behind a login page using curl is:

• Determine the login URL (the page with the login form on it).
• Open the login page in your browser.
• Use the browser's "View Source" option to look at the HTML and locate the login form. Make note of the URL that the form posts to and the names of the fields that get posted. Generally there are only 2 fields: username and password (although they might have different names), but there may also be some hidden fields that you need to include (as well as understand what they are and what is an appropriate value to send).
• Retrieve the login page with curl. Note, that it may not actually be necessary to retrieve this page but if the page that the form posts to expects some cookies to be set, you may need to retrieve this first page so that you can create and save the cookies (which curl does for you).
• Invoke curl a second time and post the login data.
• Now invoke curl a third time passing the URL of the actual page that you want to retrieve.
• If the site has a logout link you can optionally also use curl a fourth time to retrieve the logout page to ensure that the session is closed.

The curl command below retrieves the Vonage login page:

curl --silent --cookie-jar $cookie_jar \
    --output $web_page-1 \
    http://www.vonage.com/?login

Note the --cookie-jar option, this stores any cookies required by the website in the specified file. The file to store the retrieved page is specified by the --output option.

The curl command below now posts the login data required by the login form:

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --location \
    --data "username=$username&password=$password" \
    --output $web_page-2 \
    https://secure.vonage.com/vonage-web/public/login.htm

Notice here that in addition to --cookie-jar option we also specify the --cookie option. This tells curl to use the cookie jar that we created in the first invocation as input for this invocation. We also, specify the --location option so that any redirects sent by the page are followed. The actual data to post is specified with the --data option. The values before the equals signs in the data are the fields names from the login form, the values after are the appropriate field values to post.

The following two curl commands now retrieve the billing page and logout from Vonage:

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --output $web_page-3 \
    https://secure.vonage.com/webaccount/billing/index.htm

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --location \
    --output $web_page-4 \
    https://secure.vonage.com/webaccount/public/logoff.htm

All that's left now is to extract the account balance from the billing page (the third page that we retrieved). After looking at the returned HTML, I was able to see where the data I wanted was located and determine a way to filter out all the extraneous information using grep and sed:

echo Phone bill: $(grep 'td_value_total_amount' $web_page-3 | sed -e 's/.*>\$//' -e 's/<.*//')

The following shows a sample run of the script:

$ sh check-vonage.sh


Phone bill: 12.50

The entire script follows:

#!/bin/bash

cookie_jar=cookies.tmp
web_page=vonage.tmp
username=USERNAME
password=PASSWORD

trap "rm -f $cookie_jar $web_page-*" EXIT

curl --silent --cookie-jar $cookie_jar \
    --output $web_page-1 \
    http://www.vonage.com/?login

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --location \
    --data "username=$username&password=$password" \
    --output $web_page-2 \
    https://secure.vonage.com/vonage-web/public/login.htm

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --output $web_page-3 \
    https://secure.vonage.com/webaccount/billing/index.htm

curl --silent --cookie $cookie_jar --cookie-jar $cookie_jar \
    --location \
    --output $web_page-4 \
    https://secure.vonage.com/webaccount/public/logoff.htm

echo
echo
echo Phone bill: $(grep 'td_value_total_amount' $web_page-3 | sed -e 's/.*>\$//' -e 's/<.*//')