1. 首先加载包，创建函数getParams函数（用于从带参数的url中提取postForm的参数，带参数的url可以用Firefox的firebug中复制下来）

library(RCurl)
library(XML)
library(magrittr)
getParams <- function(url, 
                      containURL = substr(url, 1, 4) == "http"){
  str_find_first <- function(str, pattern)
    regexpr(pattern, str) %>% {list(pos = as.numeric(.), len = attr(., "match.length"))}

  str_split_first <- function(str, pattern){
    pos <- str_find_first(str, pattern)
    if (pos$pos < 0) return(set_names(list(""), str))
    set_names(list(substr(str, pos$pos + pos$len, nchar(str))), substr(str, 1, pos$pos - 1))
  }
  url <- iconv(URLdecode(url), "utf-8", "gbk")
  if (containURL){
    pos <- str_find_first(url, "\\?")
    if (pos$pos > 0) url <- substr(url, pos$pos + 1, nchar(url))
  }
  abcd <- strsplit(url,"&")[[1]]
  params <- lapply(abcd, str_split_first, pattern="\\=") %>% do.call(c,.)
  return(params)
}

2. 然后带上百宝箱curlhand上路，行走江湖必备

## please input your password here
user <- "kongdd"
pwd <- "****"
myHttpheader<- c(
  "User-Agent" = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0",
  "Accept" = "text/html,application/xhtml+xml,application/xml,application/json;q=0.9,*/*;q=0.8",
  "Accept-Language" = "zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3",
  "Connection"="keep-alive",
  "Host" = "cos.name")
ch <- getCurlHandle()#带上百宝箱开始上路
curlSetOpt(curl = ch, ssl.verifypeer = FALSE, 
           followlocation = TRUE,
           verbose = TRUE,
           cookiejar = "cookies_cnki.txt", #cookiefile = "cookies_cnki.txt", 
           httpheader = myHttpheader)
url_login <- 'http://cos.name/cn/wp-login.php'
# (1) first call to initializate session. you get the session cookie
page <- getURL(url_login, curl = ch)

3. 构造提交的表单的参数

post1 <- "log=user&pwd=pwd&pTE-gB-H-f-O-c-V=WPZKteIRNC9n9nwYjh758ig-mtHo4KXjrryHb0Ag1SDIlN8TZsEWs7U6qLAUWxhUCPXuED8XoSLBtNqkQSln9ONpRCdW0YfjXEfbGUf-9Echd4sR6YIwQHLfWdLAFVra&wp-submit=%E7%99%BB%E5%BD%95&redirect_to=http%3A%2F%2Fcos.name%2Fcn%2F&testcookie=1&y-v-F-FV-A-MP-U-Rh=10809510.020100101"
params1 <- getParams(post1)
params1$log <- user
params1$pwd <- pwd
# 其他尝试
# post2 <- "http://cos.name/cn/wp-admin/admin-ajax.php?action=gdbcRetrieveToken&browserInfo=%7B%22screenWidth%22%3A1920%2C%22screenHeight%22%3A1080%2C%22engine%22%3A24%2C%22features%22%3A95%2C%22mozilla%22%3A%225.0%22%2C%22windows_nt%22%3A%2210.0%22%2C%22wow64%22%3Atrue%2C%22rv%22%3A%2250.0%22%2C%22gecko%22%3A%2220100101%22%2C%22firefox%22%3A%2250.0%22%7D&pTE-gB-H-f-O-c-V=3759969693&requestTime=1480418883349"
# params2 <- getParams(post2)
# params2$requestTime <- as.character(floor(as.numeric(Sys.time())*1000))
# 
# postForm("http://cos.name/cn/wp-admin/admin-ajax.php", .params = params2, curl = ch, 
#          .opt = list(verbose = TRUE), 
#          Referer = "http://cos.name/cn/wp-login.php", style = "post")

str(params1)
List of 7
 $ log               : chr "kongdd"
 $ pwd               : chr "****"
 $ pTE-gB-H-f-O-c-V  : chr "WPZKteIRNC9n9nwYjh758ig-mtHo4KXjrryHb0Ag1SDIlN8TZsEWs7U6qLAUWxhUCPXuED8XoSLBtNqkQSln9ONpRCdW0YfjXEfbGUf-9Echd4sR6YIwQHLfWdLAFVr"| __truncated__
 $ wp-submit         : chr "登录"
 $ redirect_to       : chr "http://cos.name/cn/"
 $ testcookie        : chr "1"
 $ y-v-F-FV-A-MP-U-Rh: chr "10809510.020100101"

4. 登陆并打印作者信息，如果没报错的话，你的用户名就在info中了

page <- postForm("http://cos.name/cn/wp-login.php", .params = params1, curl = ch, 
         .opt = list(verbose = TRUE), 
         Referer = "http://cos.name/cn/wp-login.php", style = "post")
## login success if your username could be find in info
info <- htmlParse(page, encoding = "utf-8") %>% {getNodeSet(., "//div[@class='bbp-logged-in']")[[1]]} %T>% print

虽然能正常登陆了，但是提交表单的参数不是很懂。
欢迎相互讨论https://github.com/kongdd/RCurl_project/