File.write for writing in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code using File.write?

Consider this Ruby code that writes to a file and then reads it back:

File.write('test.txt', 'Hello')
content = File.read('test.txt')
puts content

What will be printed?

Ruby

File.write('test.txt', 'Hello')
content = File.read('test.txt')
puts content

A test.txt

B nil

C Hello

D Error: file not found

💡 Hint

File.write writes the string to the file, and File.read reads it back.

The File.write method writes the string 'Hello' to 'test.txt'. Then File.read reads the content of the file, which is 'Hello'. So, puts prints 'Hello'.

❓ Predict Output

intermediate

What does File.write return in Ruby?

Look at this Ruby code:

result = File.write('output.txt', 'Data')

What is the value of result after this runs?

Ruby

result = File.write('output.txt', 'Data')

A The number of bytes written (4)

B The string 'Data'

C true

D nil

💡 Hint

File.write returns how many bytes it wrote to the file.

File.write returns the number of bytes written to the file. Since 'Data' has 4 characters, it returns 4.

🔧 Debug

advanced

Why does this File.write code raise an error?

What error does this Ruby code raise?

File.write(123, 'Hello')

Ruby

File.write(123, 'Hello')

A ArgumentError: wrong number of arguments

B TypeError: no implicit conversion of Integer into String

C Errno::ENOENT: No such file or directory

D No error, writes file named '123'

💡 Hint

File.write expects a string filename, not a number.

File.write expects the first argument to be a string (filename). Passing an integer causes a TypeError because Ruby cannot convert Integer to String automatically.

📝 Syntax

advanced

Which option correctly appends text to a file using File.write?

You want to add text to the end of an existing file. Which Ruby code does this correctly?

A File.write('log.txt', 'New entry', append: true)

B File.write('log.txt', 'New entry', 'a')

C File.write('log.txt', 'New entry', flags: 'w')

D File.write('log.txt', 'New entry', mode: 'a')

💡 Hint

File.write accepts options as a hash, and mode: 'a' means append.

To append text, you pass mode: 'a' as an option hash to File.write. Option D is invalid syntax, A uses a wrong option name, and D uses 'w' which overwrites the file.

🚀 Application

expert

How many bytes are written and what is the file content after this code?

Consider this Ruby code:

bytes = File.write('data.txt', "Line1\nLine2\n", mode: 'w')
content = File.read('data.txt')

What are the values of bytes and content?

Ruby

bytes = File.write('data.txt', "Line1\nLine2\n", mode: 'w')
content = File.read('data.txt')

A bytes = 12, content = "Line1\nLine2\n"

B bytes = 11, content = "Line1\nLine2"

C bytes = 12, content = "Line1 Line2"

D bytes = 10, content = "Line1\nLine2\n"

💡 Hint

Count characters including newline characters. File.write returns bytes written exactly.

The string "Line1\nLine2\n" has 12 characters (5 + 1 + 5 + 1). File.write returns 12. The file content includes the newlines exactly as written.