According to cURL documentation http://curl.haxx.se/docs/manpage.html
-v, --verbose
Makes the fetching more verbose/talkative.
But I came across
curl -vvv -u name@foo.com:password http://www.example.com
What is the difference between -v and -vvv?
tl;dr: there is no difference between -v and -vvv.
Specifying -v multiple times usually means to increase verbosity accordingly.
This is true, e.g for a software like memcached:
-v verbose (print errors/warnings while in event loop)
-vv very verbose (also print client commands/reponses)
-vvv extremely verbose (also print internal state transitions)
(behind the scenes the options parser accumulates the level of verbosity).
But with curl command-line tool this is not the case. As you can see from tool_getparam.c, passing -v simply toggles the so-called trace type to TRACE_PLAIN. Passing -vv or -vvv does the same.
Specifying -v multiple times usually means to increase verbosity accordingly. So in this case you'd expect a very verbose output (-v specified three times).
来源：https://stackoverflow.com/questions/24402473/what-is-meaning-of-vvv-option-in-curl-request