Posts in the “ruby” category

A Ruby Monte Carlo simulation of coin flips

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.)

How to append text to a file with Ruby

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:

Ruby “glob”: How to process each file in a directory that matches a certain pattern

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:

A Ruby script to remove binary (garbage) characters from a text file

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 “execute shell command” examples

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:

A Ruby temporary file example

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.

How to process every line in a text file with Ruby

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.readlines(file).each do |line|
  puts line

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.

Ruby stdout and stderr

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.

Ruby - How to convert characters to ASCII decimal (byte) values

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.


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 command line arguments

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:

Ruby developer jobs

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.

eXtreme GUI Software Testing (Part 2)

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.

Ruby - How to sort an array of objects by one field

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:

The Ruby ternary operator syntax

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: