Awful thing about curl is, it exits with 0 when it gets HTTP error responses.
Workaround for this is to use these switches:
    -O or '-o filename'  To send regular output away
    -s  (No -v)            If don't want regular output along with the code.
    -w '\n%{http_code}\n'  To write the response HTTP code.  Skip first \n, for delimiting, if -s.

curl -O http://...       # works just like "wget url".  I.e. writes to file
                          # with name based on the downloaded file
curl http://..            # writes to stdout
curl -L ...               # Follow redirects
curl -k https://..        # Doesn't enforce cert check
curl -x proxy.server:80 [-U username:password]
curl -o filename http://  # is just like  "wget -O filename url"
 "-C -" "resumes" a fetch.  I think can resume from any aborted fetch.
curl -u username[:password]   # Basic Auth
curl -F name=val...   Post a value
   val from file:  'name=<filepath'
   val from file with file basename also sent to server:  'name=<filepath'
    -H 'name: val'
curl -n  # Use ~/.netrc file
curl -K path/file.rc  Additional init file IN ADDITION TO ~/[._]curlrc
curl -q # Don't use any init file
For PATCH method need to specify this though not even in man page:
   -X PATCH
File upload:
    -F dummy=@file/path[;type=mime/type];filename=uploadFile.name
Reported speeds are in *Bytes, not bits.
-v:  Verbose   vs.  -s:  Silent  vs.  --trace[-ascii] {-|FILENAME}
curlrc files (default or explicitly by -K switch)
   Man page is wrong about format.
     x=y  does not work.  Must use some whitespace.
     Single quotes don't work.  Must use double-quotes for whitespace, escapes.
Can pipe JSON output to prettify it: | jq  # or python -m json.tool
(neither jq nor python doesn't come with gitforwin though. :(
PRETTY-PRINT with:  curl... | jq  # or python -m json.tool
Can do powerful post-processing with jq too.  See section in "tech/linux.txt".

(Not curl-specific)
Content-Type header specifies mime-type in THIS transfer.
Accept header specificies what mime-type we can handle in response.

post:
curl -X POST -H 'Content-Type: application/json' -d '{json...}' URL
OR
curl -X POST -H 'Content-Type: application/json' -d @file.json URL
OR

For cookies to retain CSRF or session IDs, use switch -c to write cookie file,
and -b to read (and -resend) those cookies.
See shell script .../tech/addm/code/platformScriptMon.bash for working example.

To specify http params for GET without inlining them in URL, you must use switch -G with the -d's.