libcurl

Section: libcurl url interface (3)
Updated: November 05, 2020
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NAME

libcurl-url - URL interface overview

DESCRIPTION

The URL interface provides a set of functions for parsing and generating URLs.

INCLUDE

You still only include <curl/curl.h> in your code. Note that the URL API was introduced in 7.62.0.

CREATE

Create a handle that holds URL info and resources with curl_url(3):

CURLU *h = curl_url();

CLEANUP

When done with it, clean it up with curl_url_cleanup(3):

curl_url_cleanup(h);

DUPLICATE

When you need a copy of a handle, just duplicate it with curl_url_dup(3):

CURLU *nh = curl_url_dup(h);

PARSING

By "setting" a URL to the handle with curl_url_set(3), the URL is parsed and stored in the handle. If the URL is not syntactically correct it will return an error instead.

  rc = curl_url_set(h, CURLUPART_URL,
                    "https://example.com:449/foo/bar?name=moo", 0);

The zero in the fourth argument is a bitmask for changing specific features.

If successful, this stores the URL in its individual parts within the handle.

REDIRECT

When a handle already contains info about a URL, setting a relative URL will make it "redirect" to adapt to it.

rc = curl_url_set(h, CURLUPART_URL, "../test?another", 0);

GET URL

The `CURLU` handle represents a URL and you can easily extract that with curl_url_get(3):

  char *url;
  rc = curl_url_get(h, CURLUPART_URL, &url, 0);
  curl_free(url);

The zero in the fourth argument is a bitmask for changing specific features.

GET PARTS

When a URL has been parsed or parts have been set, you can extract those pieces from the handle at any time.

  rc = curl_url_get(h, CURLUPART_HOST, &host, 0);
  rc = curl_url_get(h, CURLUPART_SCHEME, &scheme, 0);
  rc = curl_url_get(h, CURLUPART_USER, &user, 0);
  rc = curl_url_get(h, CURLUPART_PASSWORD, &password, 0);
  rc = curl_url_get(h, CURLUPART_PORT, &port, 0);
  rc = curl_url_get(h, CURLUPART_PATH, &path, 0);
  rc = curl_url_get(h, CURLUPART_QUERY, &query, 0);
  rc = curl_url_get(h, CURLUPART_FRAGMENT, &fragment, 0);

Extracted parts are not URL decoded unless the user also asks for it with the CURLU_URLDECODE flag set in the fourth bitmask argument.

Remember to free the returned string with curl_free(3) when you're done with it!

SET PARTS

A user set individual URL parts, either after having parsed a full URL or instead of parsing such.

  rc = curl_url_set(urlp, CURLUPART_HOST, "www.example.com", 0);
  rc = curl_url_set(urlp, CURLUPART_SCHEME, "https", 0);
  rc = curl_url_set(urlp, CURLUPART_USER, "john", 0);
  rc = curl_url_set(urlp, CURLUPART_PASSWORD, "doe", 0);
  rc = curl_url_set(urlp, CURLUPART_PORT, "443", 0);
  rc = curl_url_set(urlp, CURLUPART_PATH, "/index.html", 0);
  rc = curl_url_set(urlp, CURLUPART_QUERY, "name=john", 0);
  rc = curl_url_set(urlp, CURLUPART_FRAGMENT, "anchor", 0);

Set parts are not URL encoded unless the user asks for it with the `CURLU_URLENCODE` flag.

APPENDQUERY

An application can append a string to the right end of the query part with the `CURLU_APPENDQUERY` flag to curl_url_set(3).

Imagine a handle that holds the URL `https://example.com/?shoes=2`. An application can then add the string `hat=1` to the query part like this:

  rc = curl_url_set(urlp, CURLUPART_QUERY, "hat=1", CURLU_APPENDQUERY);

It will even notice the lack of an ampersand (`&`) separator so it will inject one too, and the handle's full URL will then equal `https://example.com/?shoes=2&hat=1`.

The appended string can of course also get URL encoded on add, and if asked to URL encode, the encoding process will skip the '=' character. For example, append `candy=N&N` to what we already have, and URL encode it to deal with the ampersand in the data:

  rc = curl_url_set(urlp, CURLUPART_QUERY, "candy=N&N",
                    CURLU_APPENDQUERY | CURLU_URLENCODE);

Now the URL looks like

  https://example.com/?shoes=2&hat=1&candy=N%26N`