File.readlines for line-by-line in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does File.readlines do in Ruby?

File.readlines reads a file and returns an array where each element is a line from the file.

beginner

How can you read a file line-by-line using File.readlines?

Use File.readlines('filename').each do |line| ... end to process each line one by one.

beginner

What type of object does File.readlines return?

It returns an array of strings, where each string is a line from the file including the newline character.

intermediate

How do you remove the newline character from each line read by File.readlines?

You can use line.chomp inside the loop to remove the newline character from each line.

intermediate

Why might you prefer File.readlines over File.read when processing files?

File.readlines breaks the file into lines automatically, making it easier to process line-by-line without manual splitting.

What does File.readlines('file.txt') return?

A An integer count of lines

B A single string with the whole file content

C A file object

D An array of lines from the file

File.readlines returns an array where each element is a line from the file.

How do you iterate over each line after using File.readlines?

A Using <code>.each do |line| ... end</code>

B Using <code>.split</code>

C Using <code>.readline</code>

D Using <code>.open</code>

You use .each to loop through the array of lines.

Which method removes the newline character from a string in Ruby?

A <code>strip</code>

B <code>chomp</code>

C <code>delete</code>

D <code>split</code>

chomp removes the trailing newline character from a string.

If you want to read a file line-by-line without loading all lines at once, which method is better than File.readlines?

A <code>File.read</code>

B <code>File.write</code>

C <code>File.foreach</code>

D <code>File.open</code>

File.foreach reads the file line-by-line without loading the entire file into memory.

What will File.readlines('file.txt')[0] return?

A The first line of the file as a string

B The first character of the file

C The number of lines in the file

D An error

It returns the first line of the file as a string, including the newline character.

Explain how to use File.readlines to read a file and print each line without the newline character.

Think about reading lines into an array and looping through it.

Describe the difference between File.readlines and File.foreach when reading files line-by-line.

Consider memory usage and when lines are loaded.