How to determine if a url object returns '404 Not Found'?

Question

Simply put: if

x <- read.csv(url)

exists, then R will return the contents of that url. A good example, if you want to try it, might be

Answer 1

You could use the RCurl package:

R> library(RCurl)
Loading required package: bitops
R> url.exists("http://google.com")
[1] TRUE
R> url.exists("http://csgillespie.org")
[1] FALSE

Alternatively, you could use the httr package

R> library(httr)
R> http_status(GET("http://google.com"))
$category
[1] "success"

$message
[1] "success: (200) OK"

R> http_status(GET("http://csgillespie.org"))
$category
[1] "server error"

$message
[1] "server error: (503) Service Unavailable"