Provided by: libcurl4-doc_7.58.0-2ubuntu3.24_all 
NAME
CURLOPT_URL - provide the URL to use in the request
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 zero terminated string
which must be URL-encoded in the following format:
scheme://host:port/path
For a greater explanation of the format please see RFC3986.
libcurl doesn't validate the syntax or use this variable until the transfer is issued. Even if you set a
crazy value here, curl_easy_setopt(3) will still return CURLE_OK.
If the given URL is missing a scheme name (such as "http://" or "ftp://" etc) then libcurl will make a
guess based on the host. If the outermost sub-domain name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP
then that protocol will be used, otherwise HTTP will be 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 that specified by the scheme or deduced by libcurl from the host name, not be
supported by libcurl then CURLE_UNSUPPORTED_PROTOCOL will be 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(3) can be used to limit what protocols libcurl will 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.
CURLOPT_URL(3) is the only option that must be set before a transfer is started.
The host part of the URL contains the address of the server that you want to connect to. This can be the
fully qualified domain name of the server, the local network name of the machine on your network or the
IP address of the server or machine represented by either an IPv4 or IPv6 address. For example:
http://www.example.com/
http://hostname/
http://192.168.0.1/
http://[2001:1890:1112:1::20]/
It is also possible to specify the user name, password and any supported login options as part of the
host, for the following protocols, when connecting to servers that require authentication:
http://user:password@www.example.com
ftp://user:password@ftp.example.com
smb://domain%2fuser:password@server.example.com
imap://user:password;options@mail.example.com
pop3://user:password;options@mail.example.com
smtp://user:password;options@mail.example.com
At present only IMAP, POP3 and SMTP support login options as part of the host. For more information
about the login options in URL syntax please see RFC2384, RFC5092 and IETF draft draft-earhart-url-
smtp-00.txt (Added in 7.31.0).
The port is optional and when not specified libcurl will use the default port based on the determined or
specified protocol: 80 for HTTP, 21 for FTP and 25 for SMTP, etc. The following examples show how to
specify the port:
http://www.example.com:8080/ - This will connect to a web server using port 8080 rather than 80.
smtp://mail.example.com:587/ - This will connect to a SMTP server on the alternative mail port.
The path part of the URL is protocol specific and whilst some examples are given below this list is not
conclusive:
HTTP The path part of a HTTP request specifies the file to retrieve and from what directory. If the
directory is not specified then the web server's root directory is used. If the file is omitted
then the default document will be retrieved for either the directory specified or the root
directory. The exact resource returned for each URL is entirely dependent on the server's
configuration.
http://www.example.com - This gets the main page from the web server.
http://www.example.com/index.html - This returns the main page by explicitly requesting it.
http://www.example.com/contactus/ - This returns the default document from the contactus
directory.
FTP The path part of an FTP request specifies the file to retrieve and from what directory. If the
file part is omitted then libcurl downloads the directory listing for the directory specified. If
the directory is omitted then the directory listing for the root / home directory will be
returned.
ftp://ftp.example.com - This retrieves the directory listing for the root directory.
ftp://ftp.example.com/readme.txt - This downloads the file readme.txt from the root directory.
ftp://ftp.example.com/libcurl/readme.txt - This downloads readme.txt from the libcurl directory.
ftp://user:password@ftp.example.com/readme.txt - This retrieves the readme.txt file from the
user's home directory. When a username and password is specified, everything that is specified in
the path part is relative to the user's home directory. To retrieve files from the root directory
or a directory underneath the root directory then the absolute path must be specified by
prepending an additional forward slash to the beginning of the path.
ftp://user:password@ftp.example.com//readme.txt - This retrieves the readme.txt from the root
directory when logging in as a specified user.
SMTP The path part of a SMTP request specifies the host name to present during communication with the
mail server. If the path is omitted then libcurl will attempt to resolve the local computer's host
name. However, this may not return the fully qualified domain name that is required by some mail
servers and specifying this path allows you to set an alternative name, such as your machine's
fully qualified domain name, which you might have obtained from an external function such as
gethostname or getaddrinfo.
smtp://mail.example.com - This connects to the mail server at example.com and sends your local
computer's host name in the HELO / EHLO command.
smtp://mail.example.com/client.example.com - This will send client.example.com in the HELO / EHLO
command to the mail server at example.com.
POP3 The path part of a POP3 request specifies the message ID to retrieve. If the ID is not specified
then a list of waiting messages is returned instead.
pop3://user:password@mail.example.com - This lists the available messages for the user
pop3://user:password@mail.example.com/1 - This retrieves the first message for the user
IMAP The path part of an IMAP request not only specifies the mailbox to list (Added in 7.30.0) or
select, but can also be used to check the UIDVALIDITY of the mailbox, to specify the UID, SECTION
(Added in 7.30.0) and PARTIAL octets (Added in 7.37.0) of the message to fetch and to specify what
messages to search for (Added in 7.37.0).
imap://user:password@mail.example.com - Performs a top level folder list
imap://user:password@mail.example.com/INBOX - Performs a folder list on the user's inbox
imap://user:password@mail.example.com/INBOX/;UID=1 - Selects the user's inbox and fetches message
1
imap://user:password@mail.example.com/INBOX;UIDVALIDITY=50/;UID=2 - Selects the user's inbox,
checks the UIDVALIDITY of the mailbox is 50 and fetches message 2 if it is
imap://user:password@mail.example.com/INBOX/;UID=3/;SECTION=TEXT - Selects the user's inbox and
fetches the text portion of message 3
imap://user:password@mail.example.com/INBOX/;UID=4/;PARTIAL=0.1024 - Selects the user's inbox and
fetches the first 1024 octets of message 4
imap://user:password@mail.example.com/INBOX?NEW - Selects the user's inbox and checks for NEW
messages
imap://user:password@mail.example.com/INBOX?SUBJECT%20shadows - Selects the user's inbox and
searches for messages containing "shadows" in the subject line
For more information about the individual components of an IMAP URL please see RFC5092.
SCP The path part of a SCP request specifies the file to retrieve and from what directory. The file
part may not be omitted. The file is taken as an absolute path from the root directory on the
server. To specify a path relative to the user's home directory on the server, prepend ~/ to the
path portion. If the user name is not embedded in the URL, it can be set with the
CURLOPT_USERPWD(3) or CURLOPT_USERNAME(3) option.
scp://user@example.com/etc/issue - This specifies the file /etc/issue
scp://example.com/~/my-file - This specifies the file my-file in the user's home directory on the
server
SFTP The path part of a SFTP request specifies the file to retrieve and from what directory. If the
file part is omitted then libcurl downloads the directory listing for the directory specified. If
the path ends in a / then a directory listing is returned instead of a file. If the path is
omitted entirely then the directory listing for the root / home directory will be returned. If
the user name is not embedded in the URL, it can be set with the CURLOPT_USERPWD(3) or
CURLOPT_USERNAME(3) option.
sftp://user:password@example.com/etc/issue - This specifies the file /etc/issue
sftp://user@example.com/~/my-file - This specifies the file my-file in the user's home directory
sftp://ssh.example.com/~/Documents/ - This requests a directory listing of the Documents directory
under the user's home directory
SMB The path part of a SMB request specifies the file to retrieve and from what share and directory or
the share to upload to and as such, may not be omitted. If the user name is not embedded in the
URL, it can be set with the CURLOPT_USERPWD(3) or CURLOPT_USERNAME(3) option. If the user name is
embedded in the URL then it must contain the domain name and as such, the backslash must be URL
encoded as %2f.
smb://server.example.com/files/issue - This specifies the file "issue" located in the root of the
"files" share
smb://server.example.com/files/ -T issue - This specifies the file "issue" will be uploaded to the
root of the "files" share.
LDAP The path part of a LDAP request can be used to specify the: Distinguished Name, Attributes, Scope,
Filter and Extension for a LDAP search. Each field is separated by a question mark and when that
field is not required an empty string with the question mark separator should be included.
ldap://ldap.example.com/o=My%20Organisation - This will perform a LDAP search with the DN as My
Organisation.
ldap://ldap.example.com/o=My%20Organisation?postalAddress - This will perform the same search but
will only return postalAddress attributes.
ldap://ldap.example.com/?rootDomainNamingContext - This specifies an empty DN and requests
information about the rootDomainNamingContext attribute for an Active Directory server.
For more information about the individual components of a LDAP URL please see RFC4516.
RTMP There's no official URL spec for RTMP so libcurl uses the URL syntax supported by the underlying
librtmp library. It has a syntax where it wants a traditional URL, followed by a space and a
series of space-separated name=value pairs.
While space is not typically a "legal" letter, libcurl accepts them. When a user wants to pass in
a '#' (hash) character it will be treated as a fragment and get cut off by libcurl if provided
literally. You will instead have to escape it by providing it as backslash and its ASCII value in
hexadecimal: "\23".
The application does not have to keep the string around after setting this option.
DEFAULT
There is no default URL. If this option isn't 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 will bring reasons for 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 very 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(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(3) settings.
PROTOCOLS
All
EXAMPLE
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
curl_easy_perform(curl);
}
AVAILABILITY
POP3 and SMTP were added in 7.31.0
RETURN VALUE
Returns CURLE_OK on success or CURLE_OUT_OF_MEMORY if there was insufficient heap space.
Note that curl_easy_setopt(3) won't actually parse the given string so given a bad URL, it will not be
detected until curl_easy_perform(3) or similar is called.
SEE ALSO
CURLOPT_VERBOSE(3), CURLOPT_PROTOCOLS(3), CURLOPT_FORBID_REUSE(3), CURLOPT_FRESH_CONNECT(3),
curl_easy_perform(3), CURLINFO_REDIRECT_URL(3), CURLOPT_PATH_AS_IS(3),
libcurl 7.58.0 December 21, 2016 CURLOPT_URL(3)