Posts in the “ruby” category

For some reason or another today I was curious about this question: If you flipped a coin ten times, what are the odds that the coin would come up heads ten times, or tails ten times)?

I'm sure there is a way to determine this statistically, but I don't know how to do that, so, being new to Ruby, I wrote a little Ruby simulation program — essentially a Monte Carlo simulation of the problem — to find the answer. (Pretty boring, I know, but hey, I was bored, interested in learning Ruby, and didn't feel like reading any more of The Stand right now.)

Ruby file FAQ: How do I append text to a file in Ruby?

Solution: Appending text to a file with Ruby is similar to other languages: you need to open the file in "append" mode, write your data, and then close the file.

Here's a quick example that demonstrates how to append "Hello, world" to a file named myfile.out in the current directory:

I just finished a Ruby client program that gets the current weather for multiple cities, using the Yahoo! Weather RSS Feed, and then mails the output to me. (Besides demonstrating this Ruby weather capability, it also shows how to send a simple mail message using the Ruby mail API.)

Here's some sample Ruby source code that shows how to do something with every file in a directory, where you only work on filenames that match a pattern you're interested in. For example, in my case I'm only interested in processing files that end with the filename extension WMA, so this first snippet of Ruby code shows how to print out the name of each file in a directory with the WMA extension:

Problem: You have a file that should be a plain text file, but for some reason it has a bunch of non-printable binary characters (also known as garbage characters) in it, and you'd like a Ruby script that can create a clean version of the file.

Solution: I've demonstrated how to do this in another blog post by using the Unix tr command, but in case you'd like a Ruby script to clean up a file like this, I thought I'd write up a quick program and share it here.

Ruby exec FAQ: How do I execute a shell command from a Ruby script?

It's very easy to execute an external shell command from a Ruby script. Off the top of my head there are at least two ways to do this. First, you can use the traditional backtick operators. Second, you can use the %x syntax. I'll demonstrate both examples here.

Use the backtick operator

First, I'll use the backtick operator to execute a shell command. Here's how you can run a simple command, like the ls command, using Ruby and the backtick operator:

Problem: There are times when you're writing Ruby code that you need to be able to create and write information to a temporary file. If you write your own code to do this, there are a number of decisions to be made (see below), and you'd like to avoid all of that mess.

Solution: Use the Ruby Tempfile class to handle the grunt work for you.

There are quite a few ways to open a text file with Ruby and then process its contents, but this example probably shows the most concise way to do it:

# ruby sample code.
# process every line in a text file with ruby (version 1).
file='GettysburgAddress.txt'
File.readlines(file).each do |line|
  puts line
end

As you can see, this example code is very concise, and inside the processing loop you can do whatever you need to do with the line variable.

Very cool, thanks to a comment from a reader I just learned about the Ruby $stdout and $stderr variables. In short, you can write to STDOUT and STDERR in Ruby using code like this:

$stdout.puts "stdout"
$stderr.puts "stderr"

If you put those two lines in a Ruby script, and then run the script like this:

ruby test.rb > stdout 2> stderr

you'll find that the stdout and stderr files will contain the two different strings.

A few weeks ago when I upgraded my iPhone 3G to iOS 4, I hooked up my iPhone to my old Windows computer, where it was originally sync'd. Downloading my iPhone photos onto my Windows XP computer was a pain, and worse than that, in the process, the iPhone photos were pulled off the phone in some random order, so all the photos are completely out of order when I look at them in the Windows Explorer or the Mac Finder.

Problem: You have a character, or a string of characters, and you want to use a Ruby script to convert each character to its ASCII decimal (byte) value.

Solution

I just ran into this problem while working on a script to remove binary/garbage characters from a Unix text file. In short, all you have to do to convert a character in Ruby to its equivalent decimal ASCII code is use the ? operator in front of it, like this:

Ruby FAQ: How do I read command line arguments in a Ruby script (Ruby command line args)?

To read command line args in a Ruby script, use the special Ruby array ARGV to get the information you need. Here are a few examples.

1) Getting the number of command line args

To get the number of command line arguments passed in to your Ruby script, check ARGV.length, like this:

During the past year I've worked with all sorts of programming languages, technologies, and frameworks, including Ruby and Rails; Java, Spring, Struts, and JSF; and PHP, CakePHP, and Drupal.

As I mentioned in a previous blog entry (eXtreme GUI Testing, Part 1) I've been motivated to work on a project in my spare time, and I'd like to start leaking the details here.

For lack of a better name I'm currently calling this project eXtreme GUI Tester, or XGT for short. As its name implies, this is an application (actually a suite of applications) that hopes to make automated GUI testing a little more of a reality.

Here's the complete source code for a simple Ruby script which performs the following tasks:

Many times when I'm creating a prototype of an application with Ruby I'll create my classes using a simple Struct technique I learned from a friend. This technique of using the Struct class makes my code shorter, and is at least as readable as writing a class out using any other method.

Sorting an array of objects by one column in the object (class) is pretty simple with Ruby. Here's a quick demo of how I just did this when working on sorting the rows in a CSV file in a simple Ruby script.

Define the class

Step 1 in this is defining my class. So, here's the definition of my Ruby Person class:

Here's a quick example of some Ruby source code, showing how I used Ruby's ternary operator in a method that prints a CSV record for a class I defined:

Ruby CSV FAQ: Can you share some sample Ruby code to demonstrate how to read a CSV file in Ruby?

I just created a Ruby script that would open, read, and parse a simple CSV file. If you're interested in the full class definition, the full Ruby source code is available here.

But if you're just interested in seeing how to parse the records and fields of a CSV file, keep reading here.

In a previous tutorial I wrote about how to sort an array of Ruby objects by one field in the object. In today's tutorial I'd like to demonstrate how to sort an array of Ruby objects by multiple attributes (or fields) of the class contained by the array.