1ENV 2--- 3 4Operator to read environment variables. 5 6Use the syntax ``$ENV{VAR}`` to read environment variable ``VAR``. 7 8To test whether an environment variable is defined, use the signature 9``if(DEFINED ENV{<name>})`` of the :command:`if` command. 10 11See the :command:`set` and :command:`unset` commands to see how to 12write or remove environment variables. 13