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CURLOPT_URL(3) curl_easy_setopt options CURLOPT_URL(3)
CURLOPT_URL - provide the URL to use in the request
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_URL, char *URL);
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
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.
The CURLOPT_URL(3) string will be ignored if CURLOPT_CURLU(3) is set.
CURLOPT_URL(3) or CURLOPT_CURLU(3) must be set before a transfer is
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:
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:
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 an 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
http://www.example.com - This gets the main page from the web
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:firstname.lastname@example.org/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
ftp://user:email@example.com//readme.txt - This retrieves
the readme.txt from the root directory when logging in as a
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
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
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:firstname.lastname@example.org - This lists the available
messages for the user
pop3://user:email@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:firstname.lastname@example.org - Performs a top level
imap://user:email@example.com/INBOX - Performs a folder
list on the user's inbox
imap://user:firstname.lastname@example.org/INBOX/;UID=1 - Selects the
user's inbox and fetches message with uid = 1
Selects the user's inbox and fetches the first message in the
- Selects the user's inbox, checks the UIDVALIDITY of the
mailbox is 50 and fetches message 2 if it is
- Selects the user's inbox and fetches the text portion of
- Selects the user's inbox and fetches the first 1024 octets of
imap://user:email@example.com/INBOX?NEW - Selects the
user's inbox and checks for NEW messages
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://firstname.lastname@example.org/etc/issue - This specifies the file
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)
sftp://user:email@example.com/etc/issue - This specifies the
sftp://firstname.lastname@example.org/~/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
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
ldap://ldap.example.com/?rootDomainNamingContext - This
specifies an empty DN and requests information about the
rootDomainNamingContext attribute for an Active Directory
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:
The application does not have to keep the string around after setting
The string pointed to in the CURLOPT_URL(3) argument is generally
expected to be a sequence of characters using an ASCII compatible
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).
If libcurl is built without IDN support, the server name is used
exactly as specified when passed to the name resolver functions.
There is no default URL. If this option isn't set, no transfer can be
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
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.
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
POP3 and SMTP were added in 7.31.0
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.
CURLOPT_VERBOSE(3), CURLOPT_PROTOCOLS(3), CURLOPT_FORBID_REUSE(3),
CURLINFO_REDIRECT_URL(3), CURLOPT_PATH_AS_IS(3), CURLOPT_CURLU(3),
libcurl 7.65.3 November 11, 2018 CURLOPT_URL(3)