how to use ansible built-in variables

[shaoqin178]

When I use the built-in variables ansible_ssh_host, I got this error.

An exception occurred during task execution. To see the full traceback, use -vvv. The error was: ansible.errors.AnsibleUndefinedVariable: 'ansible_ssh_host' is undefined. 'ansible_ssh_host' is undefined

[sthiel-mpi]

I am unsure if I am missing something but to my knowledge, there is no ssh-specific host variable (see https://docs.ansible.com/ansible/latest/inventory_guide/intro_inventory.html). To access the hostname I usually use ansible_host or ansible_fqdn