连接时间：
curl -s -o /dev/null -w "%{time_connect} " http://www.joinpay.com
传输时间：
curl -s -o /dev/null -w "%{time_starttransfer} " http://www.joinpay.com
总时间：
curl -s -o /dev/null -w "%{time_total}
" http://www.joinpay.com
curl对网站响应时间监控：
[root@localhost script]# curl -o /dev/null -s -w "time_connect: %{time_connect}
time_starttransfer: %{time_starttransfer}
time_total: %{time_total}
" "https://www.joinpay.com"
time_connect: 0.015
time_starttransfer: 0.394
time_total: 0.433