Request header
$ curl -I https://api.github.com/user
> HTTP/2 200
> Cache-Control: private, max-age=60
> ETag: "644b5b0155e6404a9cc4bd9d8b1ae730"
> Last-Modified: Thu, 05 Jul 2012 15:31:30 GMT
> Vary: Accept, Authorization, Cookie
> X-RateLimit-Limit: 5000
> X-RateLimit-Remaining: 4996
> X-RateLimit-Reset: 1372700873
$ curl -I https://api.github.com/user -H 'If-None-Match: "644b5b0155e6404a9cc4bd9d8b1ae730"'
> HTTP/2 304
> Cache-Control: private, max-age=60
> ETag: "644b5b0155e6404a9cc4bd9d8b1ae730"
> Last-Modified: Thu, 05 Jul 2012 15:31:30 GMT
> Vary: Accept, Authorization, Cookie
> X-RateLimit-Limit: 5000
> X-RateLimit-Remaining: 4996
> X-RateLimit-Reset: 1372700873
$ curl -I https://api.github.com/user -H "If-Modified-Since: Thu, 05 Jul 2012 15:31:30 GMT"
> HTTP/2 304
> Cache-Control: private, max-age=60
> Last-Modified: Thu, 05 Jul 2012 15:31:30 GMT
> Vary: Accept, Authorization, Cookie
> X-RateLimit-Limit: 5000
> X-RateLimit-Remaining: 4996
> X-RateLimit-Reset: 1372700873