Create postgres users and databases from Chef

db_server.rb

include_recipe "postgresql::server90"

# inspiration from 
# https://gist.github.com/637579

execute "create-root-user" do
    code = <<-EOH
    psql -U postgres -c "select * from pg_user where usename='root'" | grep -c root
    EOH
    command "createuser -U postgres -s root"
    not_if code 
end

execute "create-database-user" do
    code = <<-EOH
    psql -U postgres -c "select * from pg_user where usename='#{node[:dbuser]}'" | grep -c #{node[:dbuser]}
    EOH
    command "createuser -U postgres -sw #{node[:dbuser]}"
    not_if code 
end


execute "create-database" do
    exists = <<-EOH
    psql -U postgres -c "select * from pg_database WHERE datname='#{node[:dbname]}'" | grep -c #{node[:dbname]}
    EOH
    command "createdb -U postgres -O #{node[:dbuser]} -E utf8 -T template0 #{node[:dbname]}"
    not_if exists
end
    


# content in node.json
#{ 
#  "postgresql" : {
#        "version": 9.0, 
#        "dir": "/etc/postgresql/9.0/main"
#  },
#  "dbuser": "user",
#  "dbname": "db"
#}

Only r.entries[0]['count'] == '0' worked out for me