url.exists =
function(url, ..., .opts = list(...), curl = getCurlHandle(.opts = .opts),
.header = FALSE)
{
if(length(url) > 1) {
# Really want to do this with a multi curl so asynchronous.
ap = if(.header) lapply else sapply
return(ap(url, url.exists, curl = curl, .header = .header))
}
g = basicTextGatherer()
failed = FALSE
ans = tryCatch(curlPerform(url = url, followlocation = TRUE, headerfunction = g$update,
nobody = TRUE, writefunction = g$update, curl = curl),
COULDNT_RESOLVE_HOST = function(x) failed <<- TRUE,
error = function(x) failed <<- TRUE)
if(failed)
return(FALSE)
if(grepl("^s?ftp", url)) {
return(TRUE)
} else
header = parseHTTPHeader(g$value())
if(.header)
header
else
as.integer(as.integer(header["status"])/100) == 2
}
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