MultiIO is a Ruby IO object that is composed of other IO objects. It is meant to be used as a drop-in replacement for regular IO objects like files, sockets, stdout/stderr streams etc.

This is useful, for example, when one wants to duplicate writes to multiple destinations (e.g. standard output, a file and a socket). Similarly, it can be used to read the concatenation of multiple IO sources.

Assuming we want to duplicate writes to a string buffer, stdout and a file:

> require "stringio"
> str = StringIO.new
> io = MultiIO.new(str, $stdout, File.new("foo", "w"))

> # write a message to all underlying IO objects (stdout is printed immediately
> # since it's attached to the terminal)
> io.puts "bar"
bar

> io.flush
> str.string # => "bar\n"
> File.read("foo") # => "bar\n"

This is an alpha release. Not all methods from IO are implemented yet so it can't be used in all cases as a drop-in replacement for regular IO objects.

The goal is to eventually implement the complete IO interface.

IO methods implemented:

• #close
• #flush
• #puts
• #read
• #rewind
• #write

Feel free to submit a patch if you need something that's missing.

Running the tests:

$ bundle exec rake

MultiIO is licensed under MIT. See LICENSE.