curl  --dump-header cook.txt ^
  --data "RURL=http=//www.example.com/r&user=bob&password=hello" ^
  --user-agent  "Mozilla/5.0"  ^
  http://www.example.com/login

HTTP/1.1 302 Found
Date: Thu, ******
Server: Microsoft-IIS/6.0
SERVER: ******
X-Powered-By: ASP.NET
X-AspNet-Version: 1.1.4322
Location: ******
Set-Cookie: Cookie1=; domain=******; expires=****** ******
******
******
Cache-Control: private
Content-Type: text/html; charset=iso-8859-1
Content-Length: 189

library(httr)

POST("http://www.example.com/login",
     body= list(RURL="http=//www.example.com/r",
                user="bob", password="hello"),
     user_agent("Mozilla/5.0"))

Response [http://www.example.com/error]
  Status: 411
  Content-type: text/html
<h1>Length Required</h1>

library(RCurl)
curl <- getCurlHandle()
curlSetOpt(cookiejar="/tmp/cookies.txt", curl=curl)
postForm("http://example.com/login", login="mylogin", passwd="mypasswd", curl=curl)
getURL("http://example.com/anotherpage", curl=curl)

GET("http://httpbin.org/cookies/set?a=1")
# Response [http://httpbin.org/cookies]
#   Status: 200
#   Content-type: application/json
# {
#    "cookies": {
#     "a": "1"
#   }
# }

GET("http://httpbin.org/cookies")
# Response [http://httpbin.org/cookies]
#   Status: 200
#   Content-type: application/json
# {
#   "cookies": {
#     "a": "1"
#   }
# }

### RCurl login and browse private pages ###

library("RCurl")

loginurl ="http=//www.*****"
mainurl  ="http=//www.*****"
agent    ="Mozilla/5.0"

#User account data and other login pars
pars=list(
     RURL="http=//www.*****",
     Username="*****",
     Password="*****"
)

#RCurl pars
curl = getCurlHandle()
curlSetOpt(cookiejar="cookiesk.txt",  useragent = agent, followlocation = TRUE, curl=curl)
#or simply
#curlSetOpt(cookiejar="", useragent = agent, followlocation = TRUE, curl=curl)

#post login form
web=postForm(loginurl, .params = pars, curl=curl)

#go to main url with real data
web=getURL(mainurl, curl=curl)

#parse/print content of web
#..... etc. etc.


#This has the side effect of saving cookie data to the cookiejar file
rm(curl)
gc()