# expand environment variables in parameters

# and adjust any occurence of $HOME to the home on the guest

def expand_env(value)

guest_sub_indices = []

return value unless value.is_a?(String)

while (matches = value.match(/\$([A-Za-z0-9_]+)/))

env_name = matches[1]

match_index = matches.begin(1)

# guest substitution

if value[match_index-2] == '$'

value[match_index-2] = '?'

value[match_index-1] = ''

guest_sub_indices << match_index-2

next

end

break if env_name == ""

env_val = ENV[env_name]

return nil if env_val.nil?

value = value.sub("$#{env_name}", env_val)

end

guest_sub_indices.each do |i|

value[i] = '$'

end

return value

end