Quick Date Calculations With Date

I frequently find myself needing to do quick date calculations in order to make scripts run when I want them to or how I want them to. Usually Date::Calc is just a bit too heavily, especially if it’s something as simple as a BASH script. As it happens, date is quite a powerful tool for some command line fu.

For example, to find the first and last day of last month:

FIRST_DOLM=`date -d "-1 month -$(($(date +%d)-1)) days" "+%Y-%m-%d"`
LAST_DOLM=`date -d "-$(date +%d) days" "+%Y-%m-%d"`

You can do the same thing using the date command on a mac with a slightly different set of switches:

FIRST_DOLM=`/bin/date -v1d -v-1m "+%Y-%m-%d"`
LAST_DOLM=`/bin/date -v31d -v-1m "+%Y-%m-%d"`

Both of these will produce the same results:


Testing Sessions with Digest::SHA256 Passwords In Rails

I am fairly new to Rails, but from what I have learned thus far, its fantastic. I plan on posting more obscure Rails items as I come across them.

I am writing an application that is similar in functionality to Yelp (in some ways). I have had some help along the way from a seasoned Rails vet. One of the things he helped me with was setting up the sessions_controller. He did this in such a way that I wasn’t initially sure how to write the functional tests for it. The sessions_controller contained code like this (it’s a bit more in depth than this, but this will give you the idea):

def create
    @current_user = User.find_by_username( params[:username] )
    if @current_user.nil? or Digest::SHA256.hexdigest( params[:password] + @current_user.password ) != @current_user.password_salt
      redirect_to( login_path )
      redirect_to( user_path )

So when it came time to write the functional tests for this (using fixtures), I couldn’t get away with just a user.yml like this:

    username: test_user
    password: secretuser
    firstname: General
    lastname: User
    email: test_user@user.com
    role: normal
    nickname: Mr. Testy

The reason for this is because the user table contains an extra column pertaining to the password called password_salt (which you’ll notice referenced above). Therefore my user fixture needed to look something more like this:

    username: test_user
    password: A0Mrhnu4  # secretsalt
    password_salt: 868532ea243f03c2ce5f6f99dcf9e27342c39ce51819fa0605302ab4b5c3841e
    firstname: Test
    lastname: User
    email: test_user@example.com
    role: normal
    nickname: Mr. Testy

The other fixture still has it usefulness in testing (like testing logins that won’t work), so don’t get rid of it so quickly.

How do I generate that salt and the hashed password? I’m glad you asked. I’m sure there is a better way to do it than I did, but I just went into the application, created a user and then went into the console, grabbed the user information and copied it into the fixture. Then I used the following code in my sessions_controller_test.rb for the functional test:

  def test_should_logout_and_clear_session
    post :destroy, :username => 'test_salt', :password => 'secretsalt',
      :return_to => '/'
    assert_redirected_to '/'
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