**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** File Handling and Exception Management **Topic:** Reading from and writing to files in Ruby In this topic, we'll delve into the world of file handling in Ruby, covering the essential concepts and methods for reading from and writing to files. **Why File Handling Matters** File handling is a fundamental aspect of programming, as it allows you to store and retrieve data from external sources. In Ruby, file handling is particularly straightforward, making it an excellent language for beginners and experts alike. **Opening a File in Ruby** Before you can read or write to a file, you need to open it using the `open` method. This method takes two arguments: the file path and the mode in which you want to open the file. ```ruby # Opening a file in read-only mode file = open('example.txt', 'r') # Opening a file in write-only mode file = open('example.txt', 'w') # Opening a file in read-write mode file = open('example.txt', 'r+') ``` **Modes for File Operations** Here are the common modes for file operations in Ruby: * `r` (read-only): Open a file for reading. If the file doesn't exist, an `Errno::ENOENT` exception is raised. * `w` (write-only): Open a file for writing. If the file doesn't exist, it will be created. If the file exists, its contents will be overwritten. * `r+` (read-write): Open a file for both reading and writing. * `a` (append): Open a file for appending new content. * `a+` (read-append): Open a file for reading and appending. **Reading from a File** Once you've opened a file, you can use various methods to read its contents: * `file.read`: Reads the entire file into a string. * `file.readlines`: Reads all lines from the file and returns an array of strings. * `file.readline`: Reads the next line from the file and returns a string. ```ruby # Opening a file and reading its contents file = open('example.txt', 'r') puts file.readlines file.close # Alternatively, use a block to ensure the file is closed File.open('example.txt', 'r') do |file| puts file.readlines end ``` **Writing to a File** To write to a file, use the `write` or `puts` method: ```ruby # Opening a file and writing to it file = open('example.txt', 'w') file.puts 'Hello, world!' file.close # Alternatively, use a block to ensure the file is closed File.open('example.txt', 'w') do |file| file.puts 'Hello, world!' end ``` **Common File Methods** Here are some other essential file methods: * `file.rewind`: Moves the file pointer back to the beginning of the file. * `file.eof`: Checks whether the file pointer has reached the end of the file. * `file.size`: Returns the size of the file in bytes. * `file.pos`: Returns the current file position. ```ruby file = open('example.txt', 'r') puts file.size puts file.pos file.rewind puts file.eof? file.close ``` **Conclusion and Practical Takeaways** In this topic, we've explored the fundamental concepts of file handling in Ruby. Remember to always close your files after use, either by calling `file.close` or using a block. This will prevent issues with file locking and improve overall performance. **External Resources** * [Ruby Documentation: File Class](https://ruby-doc.org/core-2.7.1/File.html) * [Ruby Tutorial: File Input/Output](https://www.tutorialspoint.com/ruby/ruby_files.htm) **Leave a Comment or Ask for Help** Have questions or need further clarification on file handling in Ruby? Leave a comment below or ask for help.