curl_parse_url {curl} | R Documentation |
Normalizing URL parser
Description
Interfaces the libcurl URL parser.
URLs are automatically normalized where possible, such as in the case of
relative paths or url-encoded queries (see examples).
When parsing hyperlinks from a HTML document, it is possible to set baseurl
to the location of the document itself such that relative links can be resolved.
Usage
curl_parse_url(url, baseurl = NULL, decode = TRUE, params = TRUE)
curl_modify_url(
url = NULL,
scheme = NULL,
host = NULL,
port = NULL,
path = NULL,
query = NULL,
fragment = NULL,
user = NULL,
password = NULL,
params = NULL
)
Arguments
url |
either URL string or list returned by curl_parse_url. Use this to modify a URL using the other parameters. |
baseurl |
use this as the parent if |
decode |
automatically url-decode output.
Set to |
params |
named character vector with http GET parameters. This will automatically
be converted to |
scheme |
string with e.g. |
host |
string with hostname. Required if no |
port |
string or number with port, e.g. |
path |
piece of the url starting with |
query |
piece of url starting with |
fragment |
part of url starting with |
user |
string with username |
password |
string with password |
Details
A valid URL contains at least a scheme and a host, other pieces are optional. If these are missing, the parser raises an error. Otherwise it returns a list with the following elements:
-
url: the normalized input URL
-
scheme: the protocol part before the
://
(required) -
host: name of host without port (required)
-
port: decimal between 0 and 65535
-
path: normalized path up till the
?
of the url -
query: search query: part between the
?
and#
of the url. Useparams
below to get individual parameters from the query. -
fragment: the hash part after the
#
of the url -
user: authentication username
-
password: authentication password
-
params: named vector with parameters from
query
if set
Each element above is either a string or NULL
, except for params
which
is always a character vector with the length equal to the number of parameters.
Note that the params
field is only usable if the query
is in the usual
application/x-www-form-urlencoded
format which is technically not part of
the RFC. Some services may use e.g. a json blob as the query, in which case
the parsed params
field here can be ignored. There is no way for the parser
to automatically infer or validate the query format, this is up to the caller.
For more details on the URL format see rfc3986 or the steps explained in the whatwg basic url parser.
On platforms that do not have a recent enough curl version (basically only RHEL-8) the Ada URL library is used as fallback. Results should be identical, though curl has nicer error messages. This is a temporary solution, we plan to remove the fallback when old systems are no longer supported.
You can use curl_modify_url()
both to modify an existing URL, or to
create new URL from scratch. Arguments get automatically URL-encoded where
needed, unless wrapped in I()
. If params
is given, this gets converted
into a application/x-www-form-urlencoded
string which overrides query
.
When modifying a URL, use an empty string ""
to unset a piece of the URL.
Examples
url <- "https://jerry:secret@google.com:888/foo/bar?test=123#bla"
curl_parse_url(url)
# Resolve relative links from a baseurl
curl_parse_url("/somelink", baseurl = url)
# Paths get normalized
curl_parse_url("https://foobar.com/foo/bar/../baz/../yolo")$url
# Also normalizes URL-encoding (these URLs are equivalent):
url1 <- "https://ja.wikipedia.org/wiki/\u5bff\u53f8"
url2 <- "https://ja.wikipedia.org/wiki/%e5%af%bf%e5%8f%b8"
curl_parse_url(url1)$path
curl_parse_url(url2)$path
curl_parse_url(url1, decode = FALSE)$path
curl_parse_url(url1, decode = FALSE)$path