如何捕获RCurl详细输出

Question

我有以下要求

library(RCurl)
res=getURL("http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=RCurl&btnG=Search",
           .opts=list(verbose = TRUE)
           )

并且想要捕获调用的详细输出(即,在R控制台中以红色打印的内容).我认为输出行是消息,因此打印到stderr().以下适用于消息

sink(textConnection("test","w"),type="message")
message("test message")
sink(stderr(),type="message")
test
#[1] "test message"

但如果我用上面给出message("test message")的RCurl请求替换,则不会res=getURL(.....).显然,RCurl的输出没有打印到stderr().它也没有打印到stdout().

那么,我如何捕获输出？

加分问题:sink(stderr(),type="message")将连接设置回R的默认值的正确方法是什么？

谢谢您的帮助!

Answer 1

你需要使用这个debugGatherer功能:

d <- debugGatherer()
x <- getURL("http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=RCurl&btnG=Search",
    debugfunction = d$update, verbose = TRUE)

然后,您可以verbose使用以下内容提取内容:

d$value()

但是,我想你只想要以下两个元素:

> cat(d$value()['text'])
About to connect() to www.google.com port 80 (#0)
  Trying 173.194.112.176... connected
Connected to www.google.com (173.194.112.176) port 80 (#0)
Connection #0 to host www.google.com left intact
Closing connection #0

> cat(d$value()['headerIn'])
HTTP/1.1 200 OK

Date: Thu, 14 Nov 2013 19:54:18 GMT

Expires: -1

Cache-Control: private, max-age=0

Content-Type: text/html; charset=ISO-8859-1

Set-Cookie: PREF=ID=783ad15e124023b0:FF=0:TM=1384458858:LM=1384458858:S=GuYBk1a3SfTJBIjh; expires=Sat, 14-Nov-2015 19:54:18 GMT; path=/; domain=.google.com

Set-Cookie: NID=67=sNsGhMCgjGZFtILEodYKCjxsi0Yio3oSA4xHakDGVHQKxG-fJlY05AlYlJf4Wwcto2HY2uP5Zt2iWxA4Dt0KUWxq14J-F-KvJ38zoBhWBWNxm6Ju0Oupl8gj41USR0PB; expires=Fri, 16-May-2014 19:54:18 GMT; path=/; domain=.google.com; HttpOnly

P3P: CP="This is not a P3P policy! See http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=151657 for more info."

Server: gws

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