The io-extra library provides a few extra IO methods that you may find handy. They are IO.closefrom, IO.fdwalk, IO.pread, IO.pwrite, IO.writev, IO#directio? and IO#directio=.

This library is not supported on MS Windows.

Support for OS X is limited. See below for details.

gem install io-extra

gem cert --add <(curl -Ls https://raw.githubusercontent.com/djberg96/io-extra/main/certs/djberg96_pub.pem)

require 'io-extra' # Do not use 'io/extra'

# Close all file descriptors from 3 up.
IO.closefrom(3)

# Inspect all the open handles
IO.fdwalk(0){ |handle|
  puts "=" * 40 
  p handle
  p handle.fileno
}

# Write an array to an IO object efficiently
IO.writev(fh.fileno, %w[a b c])

The "require 'io-extra'" is preferred over 'io/extra' because this is a mix of pure Ruby and C extension. The former require's the latter, so that way you get all the methods and constants that you expect.

You might be wondering what the difference is between my implementation of IO.closefrom and a pure Ruby version that looks something like this:

def IO.closefrom(n)
  0.upto(n) do |fd|
    IO.for_fd(fd).close
  end
end

The primary difference is that this walks all file descriptors, rather than only open file descriptors. However, I should note that this only applies if your platform supports the closefrom() function. In that case, the only advantage is speed.

You might also be wondering what the difference is between my implementation of IO.fdwalk and a pure Ruby version that looks something like this:

def IO.fdwalk(n)
  ObjectSpace.each_object(File){ |f|
    yield f if f.fileno >= n
  }
end

The primary difference is that this only closes Ruby file objects, not necessarily every file handle opened by the Ruby process. For example, handles opened via system() calls.

The OS X platform does not support closefrom() or fdwalk(). The hand- crafted IO.closefrom function will not work because the getrlimit() function on OS X does not work. Patches welcome.

As of Ruby 2.5, the IO#pread and IO#pwrite instance methods have been baked into the language. Consequently, the singleton methods that this library originally provided are now just wrappers around those instance methods.

For further documentation, see the io_extra.txt file or the inline documentation that was generated by RDoc (if you did a gem install).

The IO.writev tests fail on Solaris. Short test scripts seem to work, however. We're not sure what the issue is yet. Help wanted.

Update: As of 2018 Solaris is basically dead, so I'm not going to worry about supporting Solaris unless there's an outcry.

Please file any bug reports on the project page at https://github.com/djberg96/io-extra

Eric Wong for some great work on Linux compatibility and other fixes, as well as the code for the IO.writev method.

Apache-2.0

(C) 2003-2021 Daniel J. Berger All Rights Reserved

This package is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose.

Daniel J. Berger