файл конфигурации клиента OpenSSH (OpenSSH client configuration file)
Переменные окружения (Environment variables)
Arguments to some keywords can be expanded at runtime from
environment variables on the client by enclosing them in ${}, for
example ${HOME}/.ssh would refer to the user's .ssh directory. If
a specified environment variable does not exist then an error will
be returned and the setting for that keyword will be ignored.
The keywords CertificateFile, ControlPath, IdentityAgent,
IdentityFile, KnownHostsCommand, and UserKnownHostsFile support
environment variables. The keywords LocalForward and RemoteForward
support environment variables only for Unix domain socket paths.
