How to write to file in Ruby?

Question

I need to read the data out of database and then save it in a text file.

How can I do that in Ruby? Is there any file management system in Ruby?

Answer 1

The Ruby File class will give you the ins and outs of ::new and ::open but its parent, the IO class, gets into the depth of #read and #write.

Answer 2

Are you looking for the following?

File.open(yourfile, 'w') { |file| file.write("your text") }

Answer 3

You can use the short version:

File.write('/path/to/file', 'Some glorious content')

It returns the length written; see ::write for more details and options.

To append to the file, if it already exists, use:

File.write('/path/to/file', 'Some glorious content', mode: 'a')

Answer 4

This is preferred approach in most cases:

 File.open(yourfile, 'w') { |file| file.write("your text") }

When a block is passed to File.open, the File object will be automatically closed when the block terminates.

If you don't pass a block to File.open, you have to make sure that file is correctly closed and the content was written to file.

begin
  file = File.open("/tmp/some_file", "w")
  file.write("your text") 
rescue IOError => e
  #some error occur, dir not writable etc.
ensure
  file.close unless file.nil?
end

You can find it in documentation:

static VALUE rb_io_s_open(int argc, VALUE *argv, VALUE klass)
{
    VALUE io = rb_class_new_instance(argc, argv, klass);
    if (rb_block_given_p()) {
        return rb_ensure(rb_yield, io, io_close, io);
    }
    return io;
}

Answer 5

Zambri's answer found here is the best.

File.open("out.txt", '<OPTION>') {|f| f.write("write your stuff here") }

where your options for <OPTION> are:

r - Read only. The file must exist.

w - Create an empty file for writing.

a - Append to a file.The file is created if it does not exist.

r+ - Open a file for update both reading and writing. The file must exist.

w+ - Create an empty file for both reading and writing.

a+ - Open a file for reading and appending. The file is created if it does not exist.

In your case, w is preferable.

Answer 6

For those of us that learn by example...

Write text to a file like this:

IO.write('/tmp/msg.txt', 'hi')

BONUS INFO ...

Read it back like this

IO.read('/tmp/msg.txt')

Frequently, I want to read a file into my clipboard ***

Clipboard.copy IO.read('/tmp/msg.txt')

And other times, I want to write what's in my clipboard to a file ***

IO.write('/tmp/msg.txt', Clipboard.paste)

*** Assumes you have the clipboard gem installed

See: https://rubygems.org/gems/clipboard

Answer 7

To destroy the previous contents of the file, then write a new string to the file:

open('myfile.txt', 'w') { |f| f << "some text or data structures..." } 

To append to a file without overwriting its old contents:

open('myfile.txt', "a") { |f| f << 'I am appended string' }