Why Your Ruby Scripts Keep Breaking Files (and How to Fix Them)

File Handling in Ruby — Reading, Writing, and What Could Go Wrong

CodeCraft Diaries #9 • For Freshers, Students & Curious Developers

“If you’ve never accidentally deleted a file while testing your script, are you even a developer?”

Working with files is one of the first real-world things you’ll do in any programming language. Whether it's reading a config, logging errors, or saving user data — file I/O is everywhere.

And Ruby? Ruby makes it refreshingly simple. Until you forget to close the file... 💀

---

📖 Reading from a File

Let’s say we have a file called data.txt.

File.open("data.txt", "r") do |file|
  puts file.read
end

What’s happening here?

• "r" means “read mode”
• file.read grabs the entire content
• The block auto-closes the file (thank you, Ruby!)

---

✍️ Writing to a File

File.open("log.txt", "w") do |file|
  file.puts "This is a new log entry."
end

Note: "w" mode overwrites the file. If the file doesn’t exist? Ruby creates it. Ruby’s polite like that.

---

➕ Appending to a File

File.open("log.txt", "a") do |file|
  file.puts "Another entry added!"
end

"a" is append mode — it writes at the end without touching existing content.

---

💣 What Could Go Wrong?

• Forgetting to close the file (can cause memory leaks or locked files)
• Using the wrong mode — accidentally overwriting data with "w"
• Trying to read a file that doesn’t exist (handle it with grace!)

Use File.exist? to check first:

if File.exist?("data.txt")
  puts "File found!"
else
  puts "Oops, no file here."
end

---

🛠 Bonus: Read Line by Line

File.foreach("data.txt") do |line|
  puts line
end

Efficient for large files — reads one line at a time.

---

🧪 Mini Challenge

Write a Ruby script that takes a file name and a message from the user, and appends the message to that file. Bonus: Add a timestamp to each entry!

---

📚 Quick Recap

• "r" = Read
• "w" = Write (overwrite!)
• "a" = Append
• Always use File.open with a block to auto-close
• Check file existence before reading

---

🔗 Related Reads

• Modules & Mixins in Ruby — Sharing Code Without the Mess
• Procs and Lambdas in Ruby — The Cousins You Need to Know

---

🔜 Up Next in CodeCraft Diaries

“Error Handling in Ruby — Don’t Panic, Rescue!”
Because real code doesn’t always go as planned — and that’s okay.