Dir operations for directories in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to list all files in the current directory.

Ruby

files = Dir.[1](".")
puts files

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

Aentries

Bopen

Cread

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dir.open returns a directory object, not an array.

Dir.read is not a valid method.

Dir.list does not exist.

The Dir.entries method returns an array of all entries in the specified directory.

2fill in blank

medium

Complete the code to change the current working directory to '/tmp'.

Ruby

Dir.[1]("/tmp")

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

Aopen

Bcd

Cchange

Dchdir

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dir.open does not change directory.

Dir.cd is not a Ruby method.

Dir.change does not exist.

The Dir.chdir method changes the current working directory to the specified path.

3fill in blank

hard

Fix the error in the code to get the current working directory.

Ruby

current_dir = Dir.[1]

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

Apwd

Bpwd()

Cgetwd

Dget_current_dir

Attempts:

3 left

💡 Hint

Common Mistakes

Dir.pwd is an alias for Dir.getwd.

Dir.pwd() is invalid syntax in Ruby.

Dir.get_current_dir does not exist.

The correct method to get the current working directory is Dir.getwd.

4fill in blank

hard

Fill both blanks to create a new directory named 'test_dir' and then remove it.

Ruby

Dir.[1]("test_dir")
Dir.[2]("test_dir")

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

Amkdir

Brmdir

Cremove

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dir.remove or Dir.delete which do not exist.

Trying to remove a directory before creating it.

Dir.mkdir creates a new directory, and Dir.rmdir removes an empty directory.

5fill in blank

hard

Fill all three blanks to list all Ruby files in the current directory using a pattern.

Ruby

ruby_files = Dir.[1]("*.[2]")
ruby_files.each do |[3]|
  puts [3]
end

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

Aglob

Brb

Cfile

Dfilename

Attempts:

3 left

💡 Hint

Common Mistakes

Using Dir.entries instead of Dir.glob for pattern matching.

Using incorrect file extension.

Using a block variable name that is not consistent.

Dir.glob lists files matching a pattern. '*.rb' matches Ruby files. The block variable file represents each filename.

Practice

1. Which Ruby method lists all files and folders inside a directory including . and ..?

easy

A. Dir.chdir

B. Dir.mkdir

C. Dir.exist?

D. Dir.entries

Solution

1. Step 1: Understand the purpose of Dir.entries

   This method returns an array of all entries in the directory, including special entries . and ...

2. Step 2: Compare with other methods

   Dir.mkdir creates a directory, Dir.exist? checks if a directory exists, and Dir.chdir changes the current directory. None of these list contents.

3. Final Answer:

   Dir.entries -> Option D

4. Quick Check:

   List directory contents = Dir.entries [OK]

Hint: Use Dir.entries to list all files and folders [OK]

Common Mistakes:

• Confusing Dir.entries with Dir.mkdir
• Using Dir.exist? to list files
• Thinking Dir.chdir lists directory contents

2. Which of the following is the correct syntax to create a new directory named test_folder in Ruby?

easy

A. Dir.mkdir('test_folder')

B. Dir.create('test_folder')

C. Dir.make('test_folder')

D. Dir.new('test_folder')

Solution

1. Step 1: Recall the method to create directories

   The correct Ruby method to create a directory is Dir.mkdir.

2. Step 2: Check syntax correctness

   Dir.mkdir('test_folder') correctly creates a directory named 'test_folder'. Other options are invalid methods.

3. Final Answer:

   Dir.mkdir('test_folder') -> Option A

4. Quick Check:

   Create directory = Dir.mkdir [OK]

Hint: Use Dir.mkdir('folder_name') to create directories [OK]

Common Mistakes:

• Using Dir.create instead of Dir.mkdir
• Trying Dir.new for directory creation
• Misspelling method names

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

Dir.mkdir('sample_dir') unless Dir.exist?('sample_dir')
entries = Dir.entries('sample_dir')
puts entries.inspect

medium

A. []

B. ["sample_dir"]

C. [".", ".."]

D. Error: Directory not found

Solution

1. Step 1: Check directory creation and existence

   The code creates 'sample_dir' if it does not exist, so the directory will exist before listing entries.

2. Step 2: Understand Dir.entries output for empty directory

   An empty directory still contains special entries: . (current directory) and .. (parent directory). So, Dir.entries returns [".", ".."].

3. Final Answer:

   [".", ".."] -> Option C

4. Quick Check:

   Empty directory entries = [".", ".."] [OK]

Hint: Empty dirs always show '.' and '..' in Dir.entries [OK]

Common Mistakes:

• Expecting empty array for empty directory
• Thinking directory name appears in entries
• Assuming error if directory just created

4. Identify the error in this Ruby code snippet that tries to remove a directory:

Dir.rmdir('my_folder')
puts 'Folder removed'

medium

A. Dir.rmdir only removes non-empty directories

B. Dir.rmdir requires the directory to be empty before removal

C. Dir.rmdir should be Dir.remove

D. Dir.rmdir needs a block to execute

Solution

1. Step 1: Understand Dir.rmdir behavior

   Dir.rmdir removes only empty directories. If 'my_folder' contains files or folders, it will raise an error.

2. Step 2: Check other options for correctness

   Dir.rmdir only removes non-empty directories is wrong because it says the opposite. Dir.rmdir should be Dir.remove is invalid method name. Dir.rmdir needs a block to execute is incorrect; no block needed.

3. Final Answer:

   Dir.rmdir requires the directory to be empty before removal -> Option B

4. Quick Check:

   Dir.rmdir removes empty dirs only [OK]

Hint: Dir.rmdir only deletes empty directories [OK]

Common Mistakes:

• Trying to remove non-empty directories with Dir.rmdir
• Using wrong method name like Dir.remove
• Expecting Dir.rmdir to accept a block

5. You want to change the current working directory to projects, create a new folder new_app inside it, and then list the contents of projects. Which sequence of Ruby commands correctly does this?

hard

A. Dir.chdir('projects')
Dir.mkdir('new_app')
puts Dir.entries('.')

B. Dir.mkdir('new_app')
Dir.chdir('projects')
puts Dir.entries('new_app')

C. Dir.entries('projects')
Dir.mkdir('new_app')
Dir.chdir('new_app')

D. Dir.chdir('new_app')
Dir.mkdir('projects')
puts Dir.entries('.')

Solution

1. Step 1: Change directory to 'projects'

   Using Dir.chdir('projects') sets the current directory to 'projects'.

2. Step 2: Create 'new_app' inside 'projects'

   Dir.mkdir('new_app') creates the new folder inside the current directory.

3. Step 3: List contents of current directory

   Dir.entries('.') lists all files and folders inside 'projects', including 'new_app'.

4. Final Answer:

   Dir.chdir('projects') Dir.mkdir('new_app') puts Dir.entries('.') -> Option A

5. Quick Check:

   Change dir, create folder, list contents = Dir.chdir('projects') Dir.mkdir('new_app') puts Dir.entries('.') [OK]

Hint: Change dir first, then create folder, then list with Dir.entries('.') [OK]

Common Mistakes:

• Creating folder before changing directory
• Listing wrong directory contents
• Changing to new folder before creating it