How to write ruby script

Ruby is a better Perl and in my opinion is an essential language for system administrators.

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If you are still writing scripts in Bash, I hope this inspires you to start integrating Ruby in to your shell scripts. I will show you how you can ease in to it and make the transition very smoothly. The reason for this is to take advantage of both worlds. Ruby makes it seamless to pass data back and forth with shell commands.

There are many times when running shell commands is easier or required when there is an external command-line utilities you need to run. On the other hand, Bash syntax is quite ugly and difficult to remember, and it has very limited features. Ruby offers two tons of object-oriented power, along with tons of libraries and better syntax. We will look at how to write 'enhanced shell scripts' using Ruby and other tips on taking advantage of both worlds.

In Ruby, backticks allow shell execution to provide seamless back and forth with shell. This makes it easy to convert an existing shell script to Ruby. You can simply wrap everything in back ticks and start porting over the sections needed to Ruby. This is critical for error checking and handling Bash scripts. If you have a Bash script and you only want to run a little bit of Ruby code, you have a couple options. You can pass the code as an argument using the ruby -e flag or you can create a heredoc and pass a block of code.

If you are working in a bash script but want to execute a block of Ruby code, you can use a heredoc.

Enhanced Shell Scripting with Ruby

There are several ways to get input in to Ruby. We will look at each of these options and more. Command-line arguments are passed in through the ARGV object.

Unlike some other languages, Ruby does not include the name of the script being executed as an argument. So if you ran ruby myscript. The first argument that gets passed to the script happens. You can get and set environment variables using the ENV object. Note that any environment variables you set are lost when the Ruby script is done running.

This is similar to prompting the user for input, only the terminal output should not be echoed back for security purposes. This is only available in Ruby 2. To learn more see my tutorial Get Password in Console with Ruby. This allows flexible usage of your script with zero effort.Published: Sep 16, To document the general process of creating automated test scripts for web applications with Ruby and the WATIR testing module.

This document assumes that the reader is already familiar with the basic methods and syntax of the Ruby language and the components of an HTML based application links, forms, JavaScript, etc.

The first process to building either a manual or automated test suite is to understand the application to be tested. The easiest way to understand how an application needs to be tested is to understand the requirements to which it was built.

Documenting and maintaining functional requirements is more common now than in the past. If the application has properly maintained functional requirements then these are a very good place to start understanding what the application should do and how the users are intended to use it.

This process usually involves talking to application developers, architects, end users, functional experts, and business analysts. It is critical to have a large, diverse audience when it comes to understanding how the application is used and what business processes should be tested. Developers often have a very different perception of how an application is commonly used when compared to the actual users or functional analysts.

All tests processes, weather manual or automated, should have an associated step by step test case as its foundation. Without a clear, step by step process the test cannot be maintained and estimations of code coverage and test completion cannot be made.

how to write ruby script

It is not acceptable to think that the actual automated test script is in itself the documentation, because reverse engineering an automated script is time consuming and prone to numerous errors. There is an example of a standard manual test case in the appendix of this document. Many applications consume or create data in their normal operation. For the purposes of functional testing, both automated and manual, the state of data in the system under test should be the same from test cycle to test cycle.

Depending on what exactly the test case does, weather it consumesproduces new data, or both, there should be a data preparation and cleanup script to prepare the AUT for a test cycle and then repair the AUT after the cycle has completed. The data preparation and cleanup scripts should be run separately from the test suite in the case of a failure which breaks the test cycle. Not all test cases are necessarily good candidates for automation. Typically the most repetitive and simplest processes are good initial candidates.

Processes which involve complex data analysis and decisions by the tester are not the best cases to use as initial automation candidates. Start with test cases that have tedious, UI intensive, but condition less navigation procedures.

Move to cases that involve repetitive creation and deletion of data that can be automated through the application or direct database access. Finally try to create a suite of automated tests that cover all of the major functionality mission critical, most used, and revenue impacting of the application.

Once a specific business process is identified as a required test and documented in step-by-step format then the process of creating an automated test script from a manual test case can begin.

Take the documented test case and copy its contents into an empty Ruby script file.Let's open up our plain-text editor.

As far as possible, ensure that your editor's Tab is set to 2 spaces. We are now ready to write our first Ruby program. Code layout is pretty much up to you; indentation is not significant but using two-character indentation will make you friends in the community if you plan on distributing your code. Create a folder named, say. We shall store all our programs in this folder.

Our first program will display the string 'Hello' on the command window and the name of the program will be say phello.

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By convention, Ruby source files have the. In Microsoft Windows, Ruby source files sometimes end with. For example, Foo class has name foo. Give the name phello. To run your program, open a command window and type ruby phello. Note : Ruby is a scripting language. There is no special main method in Ruby from which execution begins.

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The Ruby interpreter is given a script of statements to execute, and it begins executing at the first line and continues to the last line. Parentheses are usually optional with a method call. These calls are all valid: foobar foobar foobar a, b, c foobar a, b, c b. In Ruby, everything from an integer to a string is considered to be an object more on this later.

And each object has built in 'methods' Ruby term for functions which can be used to do various useful things. To use a method, you need to put a dot after the object, and then append the method name. Some methods such as puts and gets are available everywhere and don't need to be associated with a specific object. Technically speaking, these methods are provided by Ruby's Kernel module more on this later and they are included in all Ruby objects the Kernel module is included by class more on this later Objectso its methods are available in every Ruby object.

When you run a Ruby application, an object called main of class Object is automatically created. This object provides access to the Kernel methods. I have made extensive references to information, related to Ruby, available in the public domain wikis and the blogs, articles of various Ruby Gurusmy acknowledgment and thanks to all of them. Much of the material on rubylearning.

Ruby Learning.These free mini-courses will give you a strong foundation in web development. In this lesson, we'll cover storing your methods in a separate.

You're probably tired of running your methods in IRB if that's what you're still doing so it's time to learn how to break them out into a separate script file which you can then run in its entirety from the command line. It's easy -- just create a file with the extension. You'll be able to gets from and puts to the command line now! For help, see this SO post. If you get tired of typing ruby in front of the file, you can tell your computer what to do instead.

Just let it know that the file is executable and specify that Ruby should be used to run it. This takes 2 steps:. As long as you explicitly call the filepath adding the. If you want to include a gem file a library of methods, for instance or another Ruby script in your IRB session, use require. If you've explicitly provided a path to be required, for instance. There's another method load which is almost identical to require but allows a file to be loaded multiple times.

This can be handy in IRB if you're developing a script and want to make changes to it before reloading again without having to completely quit out of IRB. While load is handy when you're playing around with command line scripts because it saves you from quitting IRB to refresh your changes, you should stick with require if you use this functionality in your own scripts.

That's because require makes sure you've only loaded the file once while, with load you might have accidental double-or-triple loads if multiple files require each other. Another thing that you'll probably want to do at some point is to access the variables that were passed to your script from the command line. For instance, if you ran:. You've passed in "howdy" and "everyone".

You access these inputs by digging into a special constant which is a variable you shouldn't try to change called ARGV.

ARGV is simply an array that contains all your command line arguments:. As you can see in the last example above, you can only pass in command line arguments from the actual command line not within IRB. There is a trick you can sometimes use to check whether your script is being run from the command line or as part of a larger program instead.

You might do so if you want to puts some stuff only if it's called from the CLI to debug it maybe. Despite learning all those options, there's one which is particularly easy.

Most modern text editors have the options to "build" or run your code right in the editor.

Welcome to the Basic Prep!

The specifics of how to do so are just a Google search away for your particular editor. There are a number of different ways to run your Ruby scripts and it's good to give each of them a try before you settle on one as your "go-to". A little bit of investment in learning these things can quickly add up to minutes and even hours of time. There are additional resources for this lesson.

Check them out! Viking Code School Prep.Get the latest tutorials on SysAdmin and open source topics. Hub for Good Supporting each other to make an impact. Write for DigitalOcean You get paid, we donate to tech non-profits. This tutorial will walk you through creating this program in Ruby. You should have a local Ruby development environment set up on your computer.

4 Ways to Write and Run a Ruby Script

Set one up by following one of these tutorials:. The puts method is then followed by a sequence of characters — Hello, World!

Any characters that are inside of quotation marks are called a string. The puts method will print this string to the screen when the program runs. Some methods, like the puts method, are included in Ruby by default. These built-in methods are always available when you create Ruby programs. You can also define your own methods. Running the ruby command launched the Ruby interpreter. The Ruby interpreter read the file you specified and evaluated its contents.

It executed the line puts "Hello, World! The string value of Hello, World!

how to write ruby script

In this example, the string Hello, World! The quotes that are on either side of Hello, World! The quotation marks delineate where the string begins and ends. Every time we run our program, it produces the same output. We can then use that name in the output. Instead of modifying your existing program, create a new program called greeting. The gets method tells the computer to wait for input from the keyboard.

This pauses the program, allowing the user to enter any text they want. All of the keystrokes, including the ENTER keystroke, are then captured and converted to a string of characters.

We use the puts method again, but this time we use a Ruby feature called string interpolationwhich lets us take the value assigned to a variable and place it inside of a string. Now run the program. The output might not exactly what you expect:. The program captured all of our keystrokes, including the ENTER key that we pressed to tell the program to continue.

But we can fix it.The Ruby programming language is becoming increasingly popular, thanks to its clean syntax, its object-oriented features, and its range of high-quality libraries and frameworks. Ruby is a powerful, yet easy-to-learn object-oriented programming language with a nice clean syntax.

It was invented in Japan in the mid-nineties, but has really taken off in recent years, largely thanks to the Ruby on Rails framework, which lets you easily write powerful dynamic websites and web apps in Ruby. As well as being popular with web developers, Ruby is also used for many other purposes, including system administration tasks and writing GUI-based desktop apps for Windows, Mac OS and Linux. This means that you need to install a Ruby interpreter to process and run your Ruby programs and scripts.

Ruby Programming Language - Full Course

There are also Ruby compilers available that can turn your Ruby code into stand-alone apps. In order to start programming in Ruby, you first need to install the Ruby interpreter on your computer.

The Ruby interpreter is the program that takes your Ruby script files and runs them. Have a Mac? Lucky you! Ruby comes pre-installed in Mac OS X.

how to write ruby script

Proceed to the next section. RubyInstaller is an app that installs a complete, self-contained Ruby environment on your PC. Installing Ruby on Linux partly depends on what distro you use. RVM is generally better at keeping your Ruby system and libraries up to date.

Read more about various ways to install Rubyand their pros and cons. Using your favourite text editor, create a new text file called greeting. Type the following text into the file:.

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Try this script out! Open your terminal window and use the cd command to change to the folder holding your greeting. Type the following:.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. For example: Selecting a file in the working directory from a list of the files matching some regular expression.

I know that I can do this sort of thing using standard bash and grep but I would be nice to be able to hack quick scripts that will work in windows and linux without me having to memorize a heap of command line programs and flags etc.

I tried to get this going but ended up getting confused about where I should be getting information such as a reference to the current directory.

So the question is what parts of the Ruby libraries do I need to know to write ruby shell scripts? By default, you already have access to Dir and Filewhich are pretty useful by themselves. Also useful from the stdlib is FileUtils.

The path to your script is also simple to get. The absolute path can be determined like that:. For file system operations I almost always use Pathname.

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This is a wrapper for many of the other file system related classes. Also useful: Dir, File Here's something important that's missing from the other answers: the command-line parameters are exposed to your Ruby shell script through the ARGV global array.

If you run into problems with getting the output of backticks, the stuff is going to standard err instead of standard out. Use this advice. You can pipe inside Ruby, too. It's a link to my blog, but it links back here so it's okay : There are probably more advanced things out there on this topic.

As other people noted, if you want to get serious there is Rush: not just as a shell replacement which is a bit too zany for me but also as a library for your use in shell scripts and programs. Go get yourself a copy of Everyday Scripting with Ruby. It has plenty of useful tips on how to do the types of things your are wanting to do.

Grep through files, find and kill processes, copy files - everything you do in the shell, now in Ruby. The above answer are interesting and very helpful when using Ruby as shell script. For me, I does not use Ruby as my daily language and I prefer to use ruby as flow control only and still use bash to do the tasks. But to turn these ruby scripts into executable scripts, put this as the first line of your ruby script:. The answer by webmat is perfect.

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