http://
, ftp://
, https://
and ftps://
.
An optional function not supported on all platforms.
curlGetHeaders(url, redirect = TRUE, verify = TRUE)
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).
It uses 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 status
of 405
.
For possible issues with secure URLs (especially on Windows) see
download.file
.
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).
capabilities("libcurl")
to see if this is supported. options
HTTPUserAgent
and timeout
are used.
## Not run: ## a not-always-available site:
# curlGetHeaders("ftps://test.rebex.net/readme.txt")
# ## End(Not run)
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