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This site gathers together all the latest tutorials (coding or otherwise) from the IT Learning Centre at Dundalk Institute of Technology.
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This version opens a file for writing, and writes its output to a file selected by the user. The second argument to open is the same as the second argument to a plain C fopen, except it will default to reading.
The object returned from open is class File.
SSL is based on the mathematical intractability of resolving a large integer into its also-large prime factors. Using this, we can encrypt information using what’s called a “private-public key pair”. Certificate authorities can issue SSL certificates that verify the authenticity of such a secured connection, and on the same note, a self-signed certificate can be produced without third-party support. By the end of the tutorial, you will have a web server accessible via HTTPS using a self-signed certificate.
The basic building block in all computers is the binary number system.
This system is chosen since it consists of 1s and 0s only. Since computers contain millions and millions of tiny ‘switches’, which must be in the ON or OFF position, this lends itself logically to the binary system. A switch in the ON position can be represented by 1; a switch in the OFF position can be represented by 0.
The built-in gets function simply reads a line and returns it as a string. The chomp method from class String trims the line terminator. The prompts are generated with ordinary prints lacking a final newline.
# Get the parts of speech
print "Please enter a past-tense verb: "
verb = gets.chomp
print "Please enter a noun: "
noun = gets.chomp
print "Please enter a proper noun: "
prop_noun = gets.chomp
print "Please enter a an adverb: "
adv = gets.chomp
# Make the sentence.
print "#{prop_noun} got a #{noun} and\n#{verb} #{adv} around the block.\n"
Similarly, the to_f method of class String converts the input string to a floating-point number.
print "Triangle height: " h = gets.to_f; print "Triangle width: " w = gets.to_f; area = 0.5*h*w print "Triangle height ", h, " width ", w, " has area ", area, "\n"
Sometimes it is nice to low ambient sound effects in the background of your website, to set a mood or for some other purpose. There are plenty of websites where you can download such files, or you can make your own. It’s best to go for something that seamlessy loops and is not to distracting to the user.
Ruby generally uses line breaks instead of semicolons to separate statements. Lines can be continued by using a \ at the end, but this is rarely needed. If the line ends with pretty much anything that suggests there should be more, Ruby will continue on to the next line. This includes such things as ending with an operator, or inside parentheses or something else which needs to be closed.
Creating and reading PDF files in Linux is easy, but manipulating existing PDF files is a little trickier. Countless applications enable you to fiddle with PDFs, but it’s hard to find a single application that does everything. The PDF Toolkit (pdftk) claims to be that all-in-one solution. It’s the closest thing to Adobe Acrobat that we’ve found for Linux.
Apache Tomcat is a web server and servlet container that is used to serve Java applications. Tomcat is an open source implementation of the Java Servlet and JavaServer Pages technologies, released by the Apache Software Foundation. This tutorial covers the basic installation and some configuration of Tomcat on your Linux server.
Having only one user, which is root, can be dangerous. Running your own personal server allows you the freedom of doing whatever you wish, so let’s make use of this by adding a user with sudo access instead of direct root access.
Ruby hashes are similar to maps or dictionaries in other languages. They are essentially arrays whose subscripts are not limited to integer values. You can create them with the curly-bracked list notation shown below, but you can also assign to a subscript expression to add members. It’s not at all unreasonable to create a hash with empty brackets, then add members using subscripting.