Manually monitor website from linux command line, curl, web

Every of this example retrieve numeric value:

curl return request time:

curl -o /dev/null -s -w %{time_total} https://www.google.com/

curl size of html:

curl -o /dev/null -s -w %{size_download} https://www.google.com/

curl return status code:

curl -o /dev/null -s -w %{http_code} https://www.google.com/

For additional commands install nmap:

apt-get install nmap -y

Check if http host is down:

nmap -p 80 www.google.com | grep "Host seems down" | wc -l

Check if https host is down:

nmap -p 443 www.google.com | grep "Host seems down" | wc -l

Using wget:

wget --spider -S "https://www.skype.com/go/getskype-full" 2>&1 | grep "HTTP/" | awk '{print $2}'