Ruby File Input And Output

File Input/Output (I/O) is an integral part of any programming language, and Ruby is no exception. Ruby makes it easy to work with files, allowing you to read from and write to them with ease. Here's a tutorial on Ruby file I/O:

1. Creating a New File:

You can create a new file using the File.new method, which also opens the file:

file = File.new("test.txt", "w")
file.close

In this example, "test.txt" is the filename and "w" is the mode (write). The file.close statement is used to close the file after we're done with it.

2. Opening and Reading from a File:

The File.open method can be used to open a file. If you provide a block, the file will automatically be closed when the block finishes:

File.open("test.txt", "r") do |file|
  while line = file.gets
    puts line
  end
end

In this example, "test.txt" is the filename and "r" is the mode (read). The file.gets statement is used to read the file line by line.

3. Writing to a File:

You can write to a file using the write method:

File.open("test.txt", "w") do |file|
  file.write "Hello, world!"
end

In this example, "test.txt" is the filename and "w" is the mode (write). The file.write statement is used to write to the file.

4. Appending to a File:

You can append to a file using the "a" mode:

File.open("test.txt", "a") do |file|
  file.puts "Hello again, world!"
end

In this example, "test.txt" is the filename and "a" is the mode (append). The file.puts statement is used to append a line to the file.

5. Reading and Writing at the Same Time:

You can open a file for both reading and writing using the "r+" mode:

File.open("test.txt", "r+") do |file|
  file.puts "Hello, world!"
  file.seek(0)  # Go back to the start of the file
  puts file.gets  # Read the first line of the file
end

In this example, "test.txt" is the filename and "r+" is the mode (read/write). The file.seek method is used to change our position in the file, and file.gets is used to read from the file.

Remember that working with files is a common source of errors in programming, because many things can go wrong. The file might not exist, you might not have permission to access it, or it might be locked by another process. Always make sure to handle these potential errors in your code to make it robust and reliable.

Reading from a file in Ruby:

File.open('filename.txt', 'r') do |file|
  content = file.read
  puts content
end

Writing to a file in Ruby:

File.open('filename.txt', 'w') do |file|
  file.puts 'Hello, world!'
end

File open and close in Ruby:

file = File.open('filename.txt', 'r')
# Do something with the file
file.close

Appending to a file in Ruby:

File.open('filename.txt', 'a') do |file|
  file.puts 'Appending new content'
end

Ruby File readlines method:

lines = File.readlines('filename.txt')
puts lines

Ruby File each_line iterator:

File.open('filename.txt', 'r') do |file|
  file.each_line do |line|
    puts line
  end
end

Reading and writing binary files in Ruby:

File.open('binaryfile.bin', 'wb') do |file|
  file.write(binary_data)
end

binary_data = File.open('binaryfile.bin', 'rb') { |file| file.read }

Ruby File I/O error handling:

begin
  File.open('nonexistent.txt', 'r') do |file|
    # Code to read from the file
  end
rescue Errno::ENOENT
  puts 'File not found!'
end

Working with CSV files in Ruby:

require 'csv'
CSV.open('data.csv', 'w') do |csv|
  csv << ['Name', 'Age']
  csv << ['John', 30]
end

File locking in Ruby:

File.open('file.txt', 'a') do |file|
  file.flock(File::LOCK_EX)  # Exclusive lock
  file.puts 'Appending with lock'
  file.flock(File::LOCK_UN)  # Release lock
end

Ruby STDOUT and STDERR:

puts 'This goes to STDOUT'
$stderr.puts 'This goes to STDERR'

Redirecting output in Ruby:

$stdout = File.new('output.txt', 'w')
puts 'This goes to output.txt'
$stdout = STDOUT  # Reset to default