Set curl options.
Generally you should only need to use this function to set CURL options
directly if there isn't already a helpful wrapper function, like
set_cookies(), add_headers() or
authenticate(). To use this function effectively requires
some knowledge of CURL, and CURL options. Use httr_options() to
see a complete list of available options. To see the libcurl documentation
for a given option, use curl_docs().
config(..., token = NULL)
| ... | named Curl options. | 
| token | An OAuth token (1.0 or 2.0) | 
Unlike Curl (and RCurl), all configuration options are per request, not per handle.
set_config() to set global config defaults, and
with_config() to temporarily run code with set options.
All known available options are listed in httr_options()
Other config: 
add_headers(),
authenticate(),
set_cookies(),
timeout(),
use_proxy(),
user_agent(),
verbose()
Other ways to set configuration: 
set_config(),
with_config()
# There are a number of ways to modify the configuration of a request
# * you can add directly to a request
HEAD("https://www.google.com", verbose())
# * you can wrap with with_config()
with_config(verbose(), HEAD("https://www.google.com"))
# * you can set global with set_config()
old <- set_config(verbose())
HEAD("https://www.google.com")
# and re-establish the previous settings with
set_config(old, override = TRUE)
HEAD("https://www.google.com")
# or
reset_config()
HEAD("https://www.google.com")
# If available, you should use a friendly httr wrapper over RCurl
# options. But you can pass Curl options (as listed in httr_options())
# in config
HEAD("https://www.google.com/", config(verbose = TRUE))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.