This function opens a connection to the specified URLs to check their validity.
Source
The source code of this function was taken from this stackoverflow discussion.
Examples
urls <- c(
     "http://www.amazon.com", "http://this.isafakelink.biz",
     "https://stackoverflow.com", "https://stackoverflow505.com")
check_url(urls)
#> [1] FALSE
check_url(urls, all_okay = FALSE)
#> [1]  TRUE FALSE  TRUE FALSE