Why file handling matters in Ruby - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file named 'example.txt' for reading.

Ruby

file = File.[1]('example.txt')

Drag options to blanks, or click blank then click option'

Awrite

Bread

Copen

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'read' instead of 'open' to start working with a file.

Trying to 'close' a file before opening it.

The File.open method is used to open a file in Ruby.

2fill in blank

medium

Complete the code to write the string 'Hello' to a file.

Ruby

File.open('greeting.txt', 'w') do |file|
  file.[1]('Hello')
end

Drag options to blanks, or click blank then click option'

Awrite

Bread

Cputs

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'read' which is for reading, not writing.

Using 'close' inside the block, which is handled automatically.

The write method writes a string to the file.

3fill in blank

hard

Fix the error in the code to read all lines from a file.

Ruby

lines = File.[1]('data.txt').readlines

Drag options to blanks, or click blank then click option'

Aputs

Bopen

Cclose

Dwrite

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call 'readlines' directly on 'write' or 'close'.

Using 'puts' which is for output, not file access.

You must open the file before calling readlines to get all lines.

4fill in blank

hard

Fill both blanks to create a hash with words as keys and their lengths as values, only for words longer than 3 characters.

Ruby

lengths = {word: word.[1] for word in words if word.[2] > 3}

Drag options to blanks, or click blank then click option'

Alength

Bsize

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'size' instead of 'length'.

Using '<' instead of '>' for filtering.

Use length to get the length of the word and > to filter words longer than 3 characters.

5fill in blank

hard

Fill all three blanks to create a hash with uppercase words as keys and their lengths as values, only for words longer than 4 characters.

Ruby

result = {word.[1]: word.[2] for word in words if word.[3] > 4}

Drag options to blanks, or click blank then click option'

Aupcase

Bsize

C>

Ddowncase

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'downcase' instead of 'upcase'.

Using '<' instead of '>' for filtering.

Use upcase to convert words to uppercase, size to get length, and > to filter words longer than 4.

Practice

1. Why is file handling important in Ruby programming?

easy

A. It allows saving and loading data outside the program

B. It speeds up the program execution automatically

C. It makes the program use less memory

D. It changes the program's user interface

Solution

1. Step 1: Understand file handling purpose

   File handling lets programs save data to files and read data back later.

2. Step 2: Identify correct purpose from options

   Only It allows saving and loading data outside the program describes saving and loading data outside the program.

3. Final Answer:

   It allows saving and loading data outside the program -> Option A

4. Quick Check:

   File handling = save/load data [OK]

Hint: File handling means saving or reading data outside program [OK]

Common Mistakes:

• Thinking file handling speeds up code
• Confusing file handling with memory management
• Believing file handling changes UI

2. Which Ruby code correctly opens a file for writing using a block?

easy

A. File.read('data.txt', 'w') do |file|
file.puts 'Hello'
end

B. File.open('data.txt', 'r') do |file|
file.puts 'Hello'
end

C. File.open('data.txt', 'w') do |file|
file.puts 'Hello'
end

D. File.write('data.txt', 'w') do |file|
file.puts 'Hello'
end

Solution

1. Step 1: Identify correct method and mode for writing

   File.open with mode 'w' opens file for writing; block syntax ensures file closes.

2. Step 2: Check each option's correctness

   File.open('data.txt', 'w') do |file| file.puts 'Hello' end uses File.open with 'w' and block correctly; others misuse methods or modes.

3. Final Answer:

   File.open('data.txt', 'w') do |file|\n file.puts 'Hello'\nend -> Option C

4. Quick Check:

   File.open + 'w' + block = correct syntax [OK]

Hint: Use File.open with 'w' mode and a block to write safely [OK]

Common Mistakes:

• Using File.read instead of File.open for writing
• Using wrong mode like 'r' for writing
• Using File.write with a block (not supported)

3. What will be the output of this Ruby code?

File.open('test.txt', 'w') { |f| f.puts 'Line 1' }
content = File.read('test.txt')
puts content

medium

A. Error: file not found

B. test.txt

C. nil

D. Line 1

Solution

1. Step 1: Write 'Line 1' to file using block

   The block writes 'Line 1' plus newline to 'test.txt' and closes file.

2. Step 2: Read file content and print

   File.read reads the file content 'Line 1\n', puts prints it as 'Line 1'.

3. Final Answer:

   Line 1 -> Option D

4. Quick Check:

   Write then read file = output written text [OK]

Hint: Write then read file prints what was saved [OK]

Common Mistakes:

• Expecting filename instead of content
• Thinking output is nil
• Assuming file not found error

4. What is wrong with this Ruby code snippet?

file = File.open('data.txt', 'r')
file.puts 'Hello'
file.close

medium

A. File opened in read mode but trying to write

B. File not closed properly

C. Missing block for File.open

D. File name is invalid

Solution

1. Step 1: Check file mode and operation

   File opened with 'r' (read) mode but code tries to write with puts, which is not allowed.

2. Step 2: Confirm other options

   File is closed properly; block is optional; filename looks valid.

3. Final Answer:

   File opened in read mode but trying to write -> Option A

4. Quick Check:

   Read mode + write operation = error [OK]

Hint: Don't write to file opened in read mode [OK]

Common Mistakes:

• Ignoring file mode mismatch
• Thinking block is always required
• Assuming file not closed

5. You want to read a file and count how many lines contain the word 'error'. Which Ruby code correctly does this using file handling?

hard

A. count = 0
file = File.open('log.txt', 'w')
file.each_line do |line|
count += 1 if line.include?('error')
end
file.close
puts count

B. count = 0
File.open('log.txt', 'r') do |file|
file.each_line do |line|
count += 1 if line.include?('error')
end
end
puts count

C. count = 0
File.read('log.txt').each do |line|
count += 1 if line.include?('error')
end
puts count

D. count = 0
File.open('log.txt') do |file|
file.read.each do |line|
count += 1 if line.include?('error')
end
end
puts count

Solution

1. Step 1: Identify correct file mode and iteration

   count = 0 File.open('log.txt', 'r') do |file| file.each_line do |line| count += 1 if line.include?('error') end end puts count opens file in 'r' mode and uses each_line with block, counting lines with 'error'.

2. Step 2: Check other options for errors

   count = 0 file = File.open('log.txt', 'w') file.each_line do |line| count += 1 if line.include?('error') end file.close puts count opens file in 'w' (write) mode, wrong for reading; count = 0 File.read('log.txt').each do |line| count += 1 if line.include?('error') end puts count uses File.read but does not handle string properly; count = 0 File.open('log.txt') do |file| file.read.each do |line| count += 1 if line.include?('error') end end puts count misses mode argument in File.open.

3. Final Answer:

   count = 0 File.open('log.txt', 'r') do |file| file.each_line do |line| count += 1 if line.include?('error') end end puts count -> Option B

4. Quick Check:

   Open file read + each_line + count lines with 'error' [OK]

Hint: Open file in 'r' mode and use each_line to count matches [OK]

Common Mistakes:

• Opening file in write mode when reading
• Not specifying mode in File.open
• Using File.read without splitting lines