Recap: curl Flags

The working set, worth committing to memory:

-s              silent: no progress meter
-i / -I         headers with the body / headers only
-o FILE         save the body (-o /dev/null to discard)
-H 'K: V'       add a request header
-X METHOD       change the method
-w '%{...}'     print facts about the transfer
--max-time N    give up after N seconds
--fail          exit non-zero on 4xx and 5xx

Two habits go with them. Always -s, because the progress meter goes to the error stream and ruins output. And keep status code and exit code apart: the first is the server's answer, the second is whether the conversation happened at all.

When something is unclear, put a listener in the way and read the request back. Guessing what was sent is always slower than looking.