Welcome back to an ongoing series called File IO in Every Language! In this installment we’ll be taking a look at doing file IO in Ruby.
Table of Contents
File IO In Ruby
As usual, we present the whole solution before we delve deeper into the code:
def write_file out = File.new("output.txt", "w") out << "This is a line written by a Ruby program\n" out << "This line also" out.flush() out.close() end def read_file in_file = File.open("output.txt", "r") in_file.each_line do |line| puts line end in_file.close() end write_file() read_file()
Before reading on, why not try to figure out how it works?
For modularity and readability, we have extracted the file writing code into its own function:
def write_file out = File.new("output.txt", "w") out << "This is a line written by a Ruby program\n" out << "This line also" out.flush() out.close() end
On the first line we call the function
out = File.new("output.txt", "w")
It takes an argument to the path of the file and a mode. A mode is how we want the file to be opened. By default, it opens for reading. We want to write abilities so we specify “w” for writing.
For the next two lines we write arbitrary text to the file:
out << "This is a line written by a Ruby program\n" out << "This line also"
In this sample code we used the bitshift left operators to write the text. We could have used the
write() method to write text instead of using the operators.
Next, we flush the file:
Sometimes when we make calls to write not everything may get written down to disk. Only a fraction could be in the file and the rest is in memory waiting to get written to the file. To ensure everything is written, we call the method
Lastly, we close the file to free up its resources:
This is something you should always do with resources when you’re done with them.
Like with the
write_file() function, we put the code for reading the file in its own function:
def read_file in_file = File.open("output.txt", "r") in_file.each_line do |line| puts line end in_file.close() end
To begin, we open a file on the first line:
in_file = File.open("output.txt", "r")
File.open() takes an argument to the path of the file and a mode. By default, it opens the file for reading purposes, but for the sake of being explicit I passed “r” for the mode.
The next three lines loop through the file and print out each line:
in_file.each_line do |line| puts line end
Finally, we close the file:
And, that’s it for reading.
Since Ruby is a scripting language, we can call the two functions we’ve just defined back-to-back at the end of our file:
And, that’ll do it!
How to Run the Solution
Websites like Repl allow you to write and run code of different programming languages in the browser. Feel free to drop our solution into one of your favorite online editors.
If you have Ruby installed on your computer/mac, you can run the following command:
To verify everything has worked correctly, you should see the contents of the file printed to the screen. In addition, the dummy file should be located alongside your script now. Feel free to check that out and let us know.
Sample Programs in Every Language
So far, we’ve covered three programming languages in this series. Naturally, we still have a long way ahead of us before we can say we’ve conquered all of the programming languages.
We appreciate it that you took your time to read this article, and we want to hear your feedback on this article and this series as a whole. Let us know how you’re feeling down below in the comments.
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If you're looking to learn some Python, I have plenty of practice problems to get you started.