Tribblix: manual page: CURLOPT

CURLOPT_URL(3) Introduction to Library Functions CURLOPT_URL(3)

NAME

CURLOPT_URL - URL for this transfer

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_URL, char *URL);

DESCRIPTION

Pass in a pointer to the URL to work with. The parameter should be a
char * to a null-terminated string which must be URL-encoded in the
following format:

scheme://host:port/path

For a greater explanation of the format please see RFC 3986.

libcurl does not validate the syntax or use the URL until the
transfer is started. Even if you set a crazy value here,
curl_easy_setopt(3) might still return CURLE_OK.

If the given URL is missing a scheme name (such as "http://" or
"ftp://" etc) then libcurl guesses based on the host. If the
outermost subdomain name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP
then that protocol gets used, otherwise HTTP is used. Since 7.45.0
guessing can be disabled by setting a default protocol, see
CURLOPT_DEFAULT_PROTOCOL(3) for details.

Should the protocol, either as specified by the URL scheme or deduced
by libcurl from the hostname, not be supported by libcurl then
CURLE_UNSUPPORTED_PROTOCOL is returned from either the
curl_easy_perform(3) or curl_multi_perform(3) functions when you call
them. Use curl_version_info(3) for detailed information of which
protocols are supported by the build of libcurl you are using.

CURLOPT_PROTOCOLS_STR(3) can be used to limit what protocols libcurl
may use for this transfer, independent of what libcurl has been
compiled to support. That may be useful if you accept the URL from an
external source and want to limit the accessibility.

The CURLOPT_URL(3) string is ignored if CURLOPT_CURLU(3) is set.

Either CURLOPT_URL(3) or CURLOPT_CURLU(3) must be set before a
transfer is started.

The application does not have to keep the string around after setting
this option.

Using this option multiple times makes the last set string override
the previous ones. Set it to NULL to disable its use again. Note
however that libcurl needs a URL set to be able to performed a
transfer.

The parser used for handling the URL set with CURLOPT_URL(3) is the
same that curl_url_set(3) uses.

ENCODING

The string pointed to in the CURLOPT_URL(3) argument is generally
expected to be a sequence of characters using an ASCII compatible
encoding.

If libcurl is built with IDN support, the server name part of the URL
can use an "international name" by using the current encoding
(according to locale) or UTF-8 (when WinIDN is used; or a Windows
Unicode build using libidn2).

If libcurl is built without IDN support, the server name is used
exactly as specified when passed to the name resolver functions.

DEFAULT

NULL. If this option is not set, no transfer can be performed.

SECURITY CONCERNS

Applications may at times find it convenient to allow users to
specify URLs for various purposes and that string would then end up
fed to this option.

Getting a URL from an external untrusted party brings several
security concerns:

If you have an application that runs as or in a server application,
getting an unfiltered URL can easily trick your application to access
a local resource instead of a remote. Protecting yourself against
localhost accesses is hard when accepting user provided URLs.

Such custom URLs can also access other ports than you planned as port
numbers are part of the regular URL format. The combination of a
local host and a custom port number can allow external users to play
tricks with your local services.

Accepting external URLs may also use other protocols than http:// or
other common ones. Restrict what accept with
CURLOPT_PROTOCOLS_STR(3).

User provided URLs can also be made to point to sites that redirect
further on (possibly to other protocols too). Consider your
CURLOPT_FOLLOWLOCATION(3) and CURLOPT_REDIR_PROTOCOLS_STR(3)
settings.

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

curl_easy_perform(curl);
}
}

AVAILABILITY

Added in curl 7.1

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).

Note that curl_easy_setopt(3) does not parse the given string so
given a bad URL, it is not detected until curl_easy_perform(3) or
similar is called.