def shebang(bin_file_name)
ruby_name = Gem::ConfigMap[:ruby_install_name] if @env_shebang
path = spec.bin_file bin_file_name
first_line = File.open(path, "rb") {|file| file.gets}
if /\A#!/ =~ first_line then
shebang = first_line.sub(/\A\#!.*?ruby\S*(?=(\s+\S+))/, "#!#{Gem.ruby}")
opts = $1
shebang.strip!
end
if not ruby_name then
"#!#{Gem.ruby}#{opts}"
elsif opts then
"#!/bin/sh\n'exec' #{ruby_name.dump} '-x' \"$0\" \"$@\"\n#{shebang}"
else
@env_path ||= ENV_PATHS.find {|env_path| File.executable? env_path }
"#!#{@env_path} #{ruby_name}"
end
end