How to determine if you have an internet connection in R

Question

Sometimes I need to download data from the internet. On occasions this has failed either because the website is down or because my computer has lost its internet connection.

Answer 1

This is a version of eyjo's answer which sacrifices accuracy for speed.

IPavailable <- function() {
  cmd <- switch(.Platform$OS.type, "windows" = "ipconfig", "ifconfig")
  any(grep("(\\d+(\\.|$)){4}", system(cmd, intern = TRUE)))
}

Answer 2

Just another one to add to the pot, inspired by @romans answer, this works only on Windows I'd assume, not sure about other platforms:

canPingSite <- function(test.site) {
    !as.logical(system(paste("ping", test.site)))
}

Which we test as follows:

> t1 <- canPingSite("www.yahoo.com")
[...]

> t2 <- canPingSite(";lkjsdflakjdlfhasdfhsad;fs;adjfsdlk")
[...]

> t1; t2
[1] TRUE
[1] FALSE

Answer 3

All these answers use packages or code outside of base R. Here's how to do it with just base R:

# IANA's test website
is_online <- function(site="http://example.com/") {
  tryCatch({
    readLines(site,n=1)
    TRUE
  },
  warning = function(w) invokeRestart("muffleWarning"),
  error = function(e) FALSE)
}