Curl for Fast Diagnostics

Sometimes, working tech support for shared web hosting, using a web browser is clunky to see what is really going on. curl is the best choice when I need to see exactly what a server is responding with. Here are the commands I use on a regular basis.

curl See the URL, no output if a redirect, no headers
curl -i See the URL with headers
curl -I See only the headers
curl -L See the URL, if it redirects, show the final destination URL
curl -iL See the URL, show headers for each redirected location, show final destination URL
curl -d "name=value" post a form value to url; can repeat option for multiple values
curl -b cookies.txt read cookie data from "cookies.txt"
curl -c cookies.txt write cookie data to "cookies.txt"
curl -b cookies.txt -c cookies.txt read cookie data from and write cookie data to "cookies.txt"
curl -u <username> use username when making the request, password is prompted on command line
watch "curl -s" repeat the curl command without spewing speed information