Feb 22 2014

Rails Error: Using Devise, I was getting “Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true”

I’ve been learning Rails for awhile now and I just recently started using Devise for user authentication. It’s been great until I got stuck on the following Error:

ArgumentError in Devise::Passwords#create

Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
Extracted source (around line #5):

Someone has requested a link to change your password. You can do this through the link below.

<%= link_to 'Change my password', edit_password_url(@resource, :reset_password_token => @token) %>

If you didn’t request this, please ignore this email.

Your password won’t change until you access the link above and create a new one.

I spent some time on Google and none of the solutions I found seemed to work at all. I was getting frustrated so I ran some updates and rebooted and sure enough, when I restarted the rails server the emails worked. It would appear the config methods in the environment files don’t reload unless the server is restarted. Hopefully this is helpful to anyone else who is going through the same thing.

The code that finally worked for me in my development.rb file (after I rebooted) was:


  config.assets.debug = true
  config.action_mailer.delivery_method = :sendmail
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.default_options = {from: 'mailer@domain.net'}
  config.action_mailer.default_url_options = {:host => "localhost:3000"}

I am using sendmail. For using smtp check The Ruby Docs

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Mar 29 2013

Multibyte php substring without the mbstring extension

In the rare case where the multibyte string (mbstring) extension is not enabled and cannot, for whatever reason, be enabled, it becomes difficult to create a substring using international characters without causing the string to be converted into gibberish.

There is a way around this using regular expressions and preg_match. If “(*UTF8)” or “/u” is used in the regular expression than the preg match will successfully return the desired substring. Two examples follow.


preg_match('/(*UTF8)^.{1,20}/',$multibyte_string,$result_array); 

preg_match('/^.{1,20}/u',$multibyte_string,$result_array); 

Ideally the mbstring functions should be used, but this serves when that is not possible

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Oct 29 2011

Starcraft 2 Videos

I’ve been playing and watching a lot of Starcraft 2 lately. It’s a bit of an addiction.

Here are two videos that I was very impressed with. The first is a summary of the pro esports scene focusing on some of the most popular players and a few of their most impressive in game plays. The second is a fan animation in the Starcraft universe.

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Jul 2 2010

Django on Dreamhost: Virtual Python Install

After writing the backend for a new web app in python I went to start working on the Django portion. I was planning on hosting this application with a Dreamhost shared hosting plan which already has Python 2.5 installed. After trying unsuccessfully to install some new middleware with easy_install, I started looking for a solution that gives me more control over what I want to do with Python without having to purchase dreamhost vps hosting. It seems that you can set up a virtual python install in your home directory and it was surprisingly easy. I’ve only had the need to use this virtual python install on Dreamhost, which is using Debian, but I can’t see any reason why it wouldn’t work on other environments.

Note that this is completely unnecessary if you have root access.

Assuming you already have a shell account and you are ssh’d in, execute these commands to install your virtual python environment:

$ wget http://peak.telecommunity.com/dist/virtual-python.py 
$ python virtual-python.py

Those commands copy the Python binary to your /home/user/bin directory and sets up symbolic links to the system wide libraries. This means that the ~/bin/python executable will have access to the same libraries as the system Python but that any extra installed software will not affect the system wide Python install.

Next you should add the ~/bin directory to your PATH by adding this block to your .bash_profile:

 if [ -d ~/bin ] ; then     
    PATH=~/bin:"${PATH}" 
fi 

You’ll have to log out and back in for this to take effect.
After you’re logged back in, run these commands to install easy_setup:
$ wget http://peak.telecommunity.com/dist/ez_setup.py 
$ python ez_setup.py 

Now you should be able to install whatever you want using easy_install. The first thing I did was install django-db-log using this command:
$ easy_install django-db-log

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May 25 2010

A Search For A Putty Alternative – Putty Tray and Putty Connection Manager

After getting my beta key for Starcraft 2 I’ve been spending a lot of time in Windows. Windows 7 is a huge improvement over Windows XP but I really miss the transparent tabbed terminals in Linux. I’ve become so used to having numerous SSH tunnels and sessions going in multiple tabs that the classic Putty Client in Windows 7 seemed very restricting. I’ve explored a few Putty alternatives and it seems that a transparent tabbed SSH client isn’t an option in Windows. I hope that there is an application that I’ve missed, but at the moment it seems you can either have a transparent Putty client with text that also becomes transparent and illegible with Putty Tray, or you can have a buggy tabbed SSH client with Putty Connection Manager. Both of these applications are less than desirable, but I have settled on Putty Tray. With Putty Tray, the console windows will minimize to the tray and not take up valuable real estate in the task bar. If used with Pageant, Putty Tray is far superior to Putty Connection Manager and it doesn’t have the usability issues that Putty Connection Manager does.

I’m still tempted to install a virtual machine and run some flavour of Linux just for the clean and visually appealing consoles.

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May 5 2010

Burning Oil Rig Or Awesome Final Fantasy Level?

I may have been playing a little to much Final Fantasy lately but this image looks exactly like it belongs in one of the gorgeous rendered cut scenes from the game.

Burning Oil Rig or Awesome Final Fantasy Level?

Burning Oil Rig or Awesome Final Fantasy Level?

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Nov 9 2009

This is How Credit Card Numbers Are Generated

I was reading an article today in one of my favorite publications about how to get free trials without actually using your credit card by generating valid credit card numbers using a simple algorithm called the Luhn check. So I wrote a little script that generates credit card numbers that will be deemed valid by most software checks. This will work because the service won’t know that the credit card is invalid until they actually try to charge it. Well, the card may be valid since my script uses random numbers. Obviously this if for informational purposes only and should never actually be used.

Most credit card numbers are validated using an algorithm called the “Luhn check”. This is a very simple algorithm that doubles the odd digits and does a sum to see if the number is divisible by 10. The credit card companies use a slightly different version that involves a check digit as the last digit. To generate a credit card number that will pass most validation software (as long as they don’t actually try to process the credit card) one only needs to follow these steps to make sure that the generated credit card is valid.

Choose 16 random numbers starting with a 3,4,5 or 6.
Starting with the first digit, double every other number.

If doubling a number results in a two digit number, add those digits together to produce a single digit number

Replace the odd digits with the new ones just created. You should now have 16 numbers consisting of all the new numbers and the original even numbers

Add up all sixteen numbers.

Manipulate the check digit so that the sum is divisible by 10.

Replace the last digit of the original random string with the new manipulated check digit.

Thats really all there is to it. Check out the source of my javascript credit card generator if you want to see how to generate and validate the credit card numbers.

The reason for starting with a 3,4,5, or 6 is that different card types start with different digit. The 3 is American Express, 4 is Visa, 5 is Master Card, 6 is a Discover Card.

Some companies use more digits to show that the card is from them. For example 5254 is a Master Card from the Bank of America and 4013 shows that it is a Visa card from Citibank. Also note that the expiry date has nothing at all to do with the card number.

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Oct 27 2009

MySQL SUM() Doesn’t Play Well With Floats

I had to write some reports for some legacy software today and I was unpleasantly surprised with the results of my SQL queries. I was selecting dollar values and summing them to for the monthly spending of certain individuals. Easy enough right? I wrote a query something like this :


SELECT SUM(t.money_spent) as sum_of_spent,
c.customer_name 
from transactions t 
join customers c on t.customer_id=c.customer_id 
group by customer_name order by c.customer_name asc

I ended up getting numerical values that were 10 decimal places long with seemingly random numbers. After checking to make sure the database didn’t have any odd entries I stumbled on this bug report.
The ‘money_spent’ column had a data type of float, which is a waste, but I still don’t think that it should sum up incorrectly. When I select individual values I get proper two decimal results.
Apparently floats and doubles use floating point math, which deals with approximate values for numbers and can thus result in confusion like this. It seems that it isn’t really possible to store 0.1 in a column of type float. You can only store 0.00999999977648258. This behavior is a little silly but easily fixed by using the ROUND() function :

SELECT SUM(ROUND(t.money_spent)) as sum_of_money_spent,
c.customer_name from transactions t 
join customers c on t.customer_id=c.customer_id 
group by customer_name order by c.customer_name asc

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Oct 21 2009

Search the wordpress content management system database

WordPress is by far the most popular content management system for blog hosting. The wordpress content management system uses the mysql database. If you have a big site with a large number of posts then it can be handy to search the content of every post to find certain text. Sometimes you may even need to replace certain keywords with other keywords. As with most content management setups there is probably a plugin that will do just that, but it is far easier to just use basic sql if you know the structure of the wordpress database.
Within either phpmyadmin or mysqlyog (depending on what you are using) you can use this sql query to find the text that you are looking for:


select * from wp_posts where post_content 
like '%content management system%';

The ID that you get back is basically the page id. For example, if I query my database and get back an id of 13449 then that content will reside at http://codytaylor.org/?p=13449. Other useful columns are the post_content which is the content text of the post, post_name which is the title of the post, and the guid which is the full url (before mod_rewrite changes it) so you don’t have to copy and paste the id and append it to your url.

If you need to search and replace some text in more than one post then you can use this sql :


UPDATE wp_posts SET post_content = REPLACE (
post_content, 'content management system', 'CMS');

That SQL query will replace the ‘content management system’ with ‘CMS’.

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Oct 7 2009

Reset Mysql Root Password On Linux

If you have root access to a linux server and you don’t have the root mysql password, but need it, then you can easily reset the root mysql password in just a few commands. These commands probably differ depending on what linux distro you use. I was using Ubuntu 9.04 (Jaunty Jackalope) when I wrote this.

Firstly you will want to turn the mysql service off.


codytaylor@server:~$ sudo /etc/init.d/mysql stop
 * Stopping MySQL database server mysqld   

Now we restart the mysql server with the ‘skip-grant-tables’ option which basically allows anyone to do whatever they like. It’s usually preferable to include the ‘skip-networking’ option so that only localhost (you) have access to the naked database.

 codytaylor@server:~$ sudo mysqld_safe --skip-grant-tables --skip-networking &

Now all that is left is actually changing the root password. Log into the mysql monitor and change the root password.

codytaylor@server:~$ mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('password') WHERE User='root';
mysql> FLUSH PRIVILEGES;

Those commands will reset the root mysql password to ‘password’. Now you’ll probably want to restart the mysql service and have it run normally.

codytaylor@server:~$ sudo /etc/init.d/mysql restart

If you are using windows and you want to reset the mysql root password then check the mysql documentation.

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