URL redirects can be glorious or annoying depending on which side of them you are on and which side you want to be on. Redirects are helpful for vanity URLs (useful in advertising) but sometimes they're annoying in that they could potentially break your code if you encounter a redirect you weren't anticipating.
The useful and amazing cURL command line utility allows you to fetch an address and return its final destination URL:
# "/css" doesn't exist but WordPress tries to find the closest match
# and then redirects to it ("/css-animation-callback")
curl -Ls -w %{url_effective} -o /dev/null http://davidwalsh.name/css
# Outputs: https://davidwalsh.name/css-animation-callback
The url_effective variable is what we're after. The L directive tells cURL to follow redirects, the s directive tells cURL to be silent (i.e. not output the page contents). You provide the URL, cURL follows it to its endpoint -- easy!