Why file handling matters in Ruby - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code that writes and reads a file?

Consider this Ruby code that writes a string to a file and then reads it back. What will it print?

Ruby

File.open('test.txt', 'w') do |file|
  file.puts 'Hello, file handling!'
end

content = File.read('test.txt')
puts content.strip

A Error: No such file or directory

B Hello, file handling!

C test.txt

D nil

💡 Hint

Think about what file.puts does and how File.read works.

The code writes the string 'Hello, file handling!' to 'test.txt' and then reads it back. The puts prints the content without extra spaces.

🧠 Conceptual

intermediate

Why is it important to close files after opening them in Ruby?

Why should you always close a file after opening it in Ruby?

A To speed up the computer's processor

B To make the file invisible on the disk

C To delete the file automatically

D To free system resources and avoid file corruption

💡 Hint

Think about what happens if too many files stay open.

Closing files frees system resources and ensures data is saved properly. Leaving files open can cause errors or data loss.

🔧 Debug

advanced

What error does this Ruby code raise when trying to read a non-existent file?

Look at this Ruby code trying to read a file that does not exist. What error will it raise?

Ruby

content = File.read('missing_file.txt')
puts content

A Errno::ENOENT (No such file or directory @ rb_sysopen - missing_file.txt)

B NoMethodError: undefined method 'read' for File

C SyntaxError: unexpected end-of-input

D TypeError: no implicit conversion of nil into String

💡 Hint

What happens when Ruby tries to open a file that isn't there?

Ruby raises an Errno::ENOENT error when a file does not exist and you try to read it.

📝 Syntax

advanced

Which Ruby code snippet correctly appends text to an existing file?

Choose the Ruby code that correctly adds the line 'Appended line' to the end of 'log.txt'.

A File.open('log.txt', 'w') { |file| file.puts 'Appended line' }

B File.read('log.txt') << 'Appended line'

C File.open('log.txt', 'a') { |file| file.puts 'Appended line' }

D File.write('log.txt', 'Appended line')

💡 Hint

Remember, 'a' mode means append, 'w' means overwrite.

Opening a file with mode 'a' appends text. Mode 'w' overwrites the file. Using File.read returns a string but does not write back. File.write overwrites the file.

🚀 Application

expert

How many lines will the file contain after running this Ruby code?

This Ruby code writes three lines to a file, then reads and appends one more line. How many lines will the file have at the end?

Ruby

File.open('data.txt', 'w') do |file|
  file.puts 'Line 1'
  file.puts 'Line 2'
  file.puts 'Line 3'
end

lines = File.readlines('data.txt')
File.open('data.txt', 'a') { |file| file.puts "Line #{lines.size + 1}" }

A 4

B 3

C 1

D 5

💡 Hint

Count the lines written first, then the appended line.

The code writes 3 lines, reads them (3 lines), then appends a 4th line labeled 'Line 4'. So the file ends with 4 lines.