Reading And Writing Text Files in Ruby

On a recent project, I had everything automated up to the point where I had to give feedback to the business analysts on what, if any, of their data had to be fixed and re-run.

I ended up writing some Ruby scripts to run through a file of transaction responses, and sort out the various error types into separate files, and produce a summary report of the error counts in each category. Now the only manual part was cutting and pasting the summary into an email, and attaching the various sorted files.

I was pleasantly surprised at how easy it was to read and write text files in Ruby. Let's say you just want to read a text file, line by line, and spit it back out, a la "cat"...

File.new(filename, "r").each { |line| puts line }

Wow, that was easy, eh? Let's try reading that file into an array for use later...

results = []
File.new(filename, "r").each { |line| results << line }

Let's say you want to capitalize everything in the file, and spit it out to a new file...

out_file = File.new("upper_case.txt","w")
results.each do |line|
  out_file.puts line.upcase
end

That was easy. It's probably obvious, but the first argument passed to the File constructor is the filename, and second is the read/write flag.

For comparison' sake, let's read a file in Java and spit it out line for line...

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
...
  BufferedReader is = new BufferedReader(new FileReader(fileName));
  String line = "";

  try {
    while (line != null)
    {
       line = is.readLine();
       System.out.println(line);
    }
 catch (Exception e) { /* do nothing for now */ }
 finally
 {
   try {is.close();}catch(Exception f) { }
 }

Definitely not "hard", but it is a bit more code. Writing a file is very similar, except of course you use FileWriter and BufferedWriter instead of FileReader and BufferedReader, and write to the file instead of reading from it.

I'm not really trying to prove anything here -- Ruby isn't better than Java, Java isn't too hard or too verbose, etc. I like Java. I like Ruby. Against my better judgment, I even like Oracle, but that's another topic. I just found that working with files was easier than I expected, even for a Ruby beginner like myself.