Add the encoding magic comment to the ruby files passed as arguments

rb-magic-comment

#!/usr/bin/env ruby
# encoding: UTF-8

ARGV.reject! { |path| !File.file?(path) }
(puts DATA.read.gsub("$0", File.basename($0)); exit 1) if ARGV.empty?

ARGV.each do |path|
  ls = IO.readlines(path)
  ix = ls[0] !~ /^#!/ ? 0 : 1
  next if ls[ix] =~ /#.*?coding\s*[:=]\s*\S/
  ls.insert ix, "# encoding: UTF-8\n", ("\n" unless ls[ix] =~ /^#?\s*\n/)
  open(path, 'w') { |f| f.write ls.join }
end

__END__
Add the unicode magic comment to ruby files.

* Files are modified in-place.
* If a file already contains a magic comment, it's skipped.
* Comment is added below the shebang if it exists, otherwise as the first line.

Usage:
  $0 file-1 [file-2 ... file-n]

Examples:
  # Add comment to standalone ruby files:
  $0 foo.rb bar.rb

  # Add comment to an entire ruby library or app:
  find . -name '*.rb' -type f -print0 | xargs -0 $0

  # Add comment to app files in a rails application:
  find app config lib -name '*.rb' -type f -print0 | xargs -0 $0