Retrieve Headers from URLs
Retrieve the headers for a URL for a supported protocol such as
An optional function not supported on all platforms.
curlGetHeaders(url, redirect = TRUE, verify = TRUE)
- character string specifying the URL.
- logical: should redirections be followed?
- logical: should certificates be verified as valid and applying to that host?
This reports what
curl -I -L or
curl -I would
report. For a
ftp:// URL the headers are a record of
the conversation between client and server before data transfer.
Only 500 header lines will be reported: there is a limit of 20 redirections so this should suffice (and even 20 would indicate problems).
getOption("timeout") for the connection
timeout: that defaults to 60 seconds. As this cannot be interrupted
you may want to consider a shorter value.
To see all the details of the interaction with the server(s) set
options(internet.info = 1).
HTTP[S] servers are allowed to refuse requests to read the headers and
some do: this will result in a
For possible issues with secure URLs (especially on Windows) see
There is a security risk in not verifying certificates, but as only the headers are captured it is slight. Usually looking at the URL in a browser will reveal what the problem is (and it may well be machine-specific).
A character vector with integer attribute
"status"(the last-received status code). If redirection occurs this will include the headers for all the URLs visited.For the interpretation of status codes see http://en.wikipedia.org/wiki/List_of_HTTP_status_codes and http://en.wikipedia.org/wiki/List_of_FTP_server_return_codes. A successful FTP connection will usually have status 250 or 350.
capabilities("libcurl") to see if this is supported.
## Not run: ## a not-always-available site: # curlGetHeaders("ftps://test.rebex.net/readme.txt") # ## End(Not run)