Use curl or wget, working with prtotocol HTTP or HTTPS:
Example:

curl http://iptest.kz/myip or

curl http://iptest.kz/showip or

curl http://iptest.kz/ip

Use wget:

Example:

wget -qO- http://iptest.kz/myip or

wget -qO- http://iptest.kz/showip or

wget -qO- http://iptest.kz/ip