Ruby File Handling Examples

Introduction to Ruby File Handling

File handling in Ruby is an essential skill for any programmer. It allows you to read from and write to files, which is crucial for data storage and manipulation. Whether you’re creating logs, saving user data, or processing text files, mastering file handling can make your projects more efficient. In this article, we’ll explore three diverse examples of Ruby file handling that will help you get started.

Example 1: Reading a Text File

Use Case

Sometimes, you need to read data from a text file, such as configuration settings or user input data. This example demonstrates how to open a file for reading and display its contents.

Code Example

## Open a file for reading
file_path = 'example.txt'

## Check if the file exists before reading
if File.exist?(file_path)
  File.open(file_path, 'r') do |file|
    file.each_line do |line|
      puts line.strip # Display each line without extra whitespace
    end
  end
else
  puts "File not found: #{file_path}"
end

Notes

• Ensure the file you want to read exists, or you’ll encounter an error.
• The each_line method helps process the file line by line, making it memory efficient for large files.

Example 2: Writing to a File

Use Case

Creating or updating a file with new data is a common task in programming. This example shows how to write to a file, either by creating a new file or appending to an existing one.

Code Example

## Define the file path
file_path = 'output.txt'

## Open a file for writing (creates a new file or overwrites)
File.open(file_path, 'w') do |file|
  file.puts "Hello, World!"
  file.puts "This is a line of text."
end

## Open the same file to append more text
File.open(file_path, 'a') do |file|
  file.puts "This line is appended to the file."
end

Notes

• The mode 'w' will overwrite the file if it already exists. Use 'a' to append data instead.
• The puts method adds a newline after each string, making it easier to read the output.

Example 3: Reading and Writing a CSV File

Use Case

Working with CSV (Comma-Separated Values) files is common when dealing with tabular data, such as spreadsheets. This example illustrates how to read from a CSV file and write to one using Ruby’s built-in CSV library.

Code Example

require 'csv'

## Define the path for the CSV file
csv_file_path = 'data.csv'

## Writing to a CSV file
CSV.open(csv_file_path, 'w') do |csv|
  csv << ['Name', 'Age', 'City'] # Header row
  csv << ['Alice', 30, 'New York']
  csv << ['Bob', 25, 'Los Angeles']
end

## Reading from the same CSV file
CSV.foreach(csv_file_path, headers: true) do |row|
  puts "Name: \\#{row['Name']}, Age: \\#{row['Age']}, City: \\#{row['City']}"
end

Notes

• The CSV library makes it easy to handle CSV data without parsing strings manually.
• Setting headers: true allows you to access each row by header names, making your code cleaner and more readable.