CURLOPT_URL(3)
CURLOPT_URL(3) curl_easy_setopt options CURLOPT_URL(3)
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 pro-
tocols 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 lib-
curl 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
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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 proto-
col: 80 for HTTP, 21 for FTP and 25 for SMTP, etc. The fol-
lowing 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
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the root directory. The exact resource returned for
each URL is entirely dependent on the server's confi-
guration.
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 omit-
ted 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 down-
loads 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 rela-
tive 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 begin-
ning 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
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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 PAR-
TIAL 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
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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
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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 speci-
fies 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.
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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 ser-
vices.
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). Con-
sider 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
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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),
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