users_from_ldap.rb

#!/usr/bin/env ruby /path/to/redmine/script/runner

login = ARGV[0]

if User.find_by_login(login)
  puts "User #{login} already exists"
  exit(1)
end

# Try all LDAP auth sources
AuthSourceLdap.all.find do |auth_source|
  attrs = auth_source.send(:get_user_dn, login)
  attrs.include?(:auth_source_id) ? attrs : nil
end

# no user found
unless attrs
  puts "User #{login} not found in LDAP."
  exit(1)
end  

# create the user in the database
user = User.new(attrs)
user.login = login
user.language = Setting.default_language
if user.save
  puts "Successfully created user #{login}."
else
  puts "An error occured during creation of user #{login}."
end