How to write to file in Ruby?

Ruby Common Questions
#1

How to write to file in Ruby?

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#2

The simplest way to write to a file in Ruby is to use the write method:

File.write('hello.txt', 'Hello, world!')

If you need to append to a file (add new data to the end of the file), you can use the append method:

File.append('hello.txt', 'Hello, world!')

If you need to read from a file, you can use the read method:

File.read('hello.txt') # => "Hello, world!"

If you need to read from a file line by line, you can use the each_line method:

File.each_line('hello.txt') do |line|
  puts line
end

This will print each line of the file to the console.

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#3

Thanks, I too was looking for a solution. This is really very helpful for me.

#4
  1. Open the file in write mode (“w” flag)
  2. Use the write method to add data to the file.
  3. If you didn’t use the block version, remember to close.
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#5 
File.append?

Are you sure?

Use this instead:

File.open('hello.txt', 'a') { |f| f.write('appended data!') }

I’m not sure if this method exists. Which Ruby version are you using?

I’d use File.foreach('hello.txt').each { |x| puts x } to read files and print line by line. Note that even if your file is 4 GB, it will only load the first line, no matter what the size is. If your first line is 4 GB, it will consume 4 GB memory at once! Use File.open('hello.txt','r').readpartial(500) to read 500 bytes from hello.txt.

There’s also IO.foreach(), but don’t use this because user’s can pipe to it. For example: IO.foreach('|whoami').first #=> "sourav\n".

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