man : url
File: url, Node: Top, Next: Getting Started, Up: (dir)
* Getting Started:: Preparing your program to use URLs.
* Retrieving URLs:: How to use this package to retrieve a URL.
* Supported URL Types:: Descriptions of URL types currently supported.
* Defining New URLs:: How to define a URL loader for a new protocol.
* General Facilities:: URLs can be cached, accessed via a gateway
and tracked in a history list.
* Customization:: Variables you can alter.
* GNU Free Documentation License:: The license for this documentation.
* Function Index::
* Variable Index::
* Concept Index::
File: url, Node: Getting Started, Next: Retrieving URLs, Prev: Top, Up: Top
1 Getting Started
"Uniform Resource Locators" (URLs) are a specific form of "Uniform
Resource Identifiers" (URI) described in RFC 2396 which updates RFC
1738 and RFC 1808. RFC 2016 defines uniform resource agents.
URIs have the form SCHEME:SCHEME-SPECIFIC-PART, where the SCHEMEs
supported by this library are described below. *Note Supported URL
FTP, NFS, HTTP, HTTPS, `rlogin', `telnet', tn3270, IRC and gopher
URLs all have the form
where `[' and `]' delimit optional parts. USERINFO sometimes takes
the form USERNAME:PASSWORD but you should beware of the security risks
of sending cleartext passwords. HOSTNAME may be a domain name or a
dotted decimal address. If the `:PORT' is omitted then the library will
use the `well known' port for that service when accessing URLs. With
the possible exception of `telnet', it is rare for ports to be
specified, and it is possible using a non-standard port may have
undesired consequences if a different service is listening on that port
(e.g., an HTTP URL specifying the SMTP port can cause mail to be sent).
The meaning of the PATH component depends on the service.
* Parsed URLs:: URLs are parsed into vector structures.
File: url, Node: Configuration, Next: Parsed URLs, Up: Getting Started
-- Variable: url-configuration-directory
The directory in which URL configuration files, the cache etc.,
reside. Default `~/.url'.
File: url, Node: Parsed URLs, Prev: Configuration, Up: Getting Started
1.2 Parsed URLs
The library functions typically operate on "parsed" versions of URLs.
These are actually vectors of the form:
[TYPE USER PASSWORD HOST PORT FILE TARGET ATTRIBUTES FULL]
is the type of the URL scheme, e.g., `http'
is the username associated with it, or `nil';
is the user password associated with it, or `nil';
is the host name associated with it, or `nil';
is the port number associated with it, or `nil';
is the `file' part of it, or `nil'. This doesn't necessarily
actually refer to a file;
is the target part, or `nil';
is the attributes associated with it, or `nil';
is `t' for a fully-specified URL, with a host part indicated by
`//' after the scheme part.
These attributes have accessors named `url-PART', where PART is the
name of one of the elements above, e.g., `url-host'. Similarly, there
are setters of the form `url-set-PART'.
There are functions for parsing and unparsing between the string and
-- Function: url-generic-parse-url url
Return a parsed version of the string URL.
-- Function: url-recreate-url url
Recreates a URL string from the parsed URL.
File: url, Node: Retrieving URLs, Next: Supported URL Types, Prev: Getting Started, Up: Top
2 Retrieving URLs
-- Function: url-retrieve-synchronously url
Retrieve URL synchronously and return a buffer containing the
data. URL is either a string or a parsed URL structure. Return
`nil' if there are no data associated with it (the case for dired,
info, or mailto URLs that need no further processing).
-- Function: url-retrieve url callback &optional cbargs
Retrieve URL asynchronously and call CALLBACK with args CBARGS
when finished. The callback is called when the object has been
completely retrieved, with the current buffer containing the
object and any MIME headers associated with it. URL is either a
string or a parsed URL structure. Returns the buffer URL will
load into, or `nil' if the process has already completed.
File: url, Node: Supported URL Types, Next: Defining New URLs, Prev: Retrieving URLs, Up: Top
3 Supported URL Types
* http/https:: Hypertext Transfer Protocol.
* file/ftp:: Local files and FTP archives.
* info:: Emacs `Info' pages.
* mailto:: Sending email.
* news/nntp/snews:: Usenet news.
* rlogin/telnet/tn3270:: Remote host connectivity.
* irc:: Internet Relay Chat.
* data:: Embedded data URLs.
* nfs:: Networked File System
* cid:: Content-ID.
* ldap:: Lightweight Directory Access Protocol
* imap:: IMAP mailboxes.
* man:: Unix man pages.
File: url, Node: http/https, Next: file/ftp, Up: Supported URL Types
3.1 `http' and `https'
The scheme `http' is Hypertext Transfer Protocol. The library supports
version 1.1, specified in RFC 2616. (This supersedes 1.0, defined in
RFC 1945) HTTP URLs have the following form, where most of the parts
The scheme `https' is a secure version of `http', with transmission
via SSL. It is defined in RFC 2069. Its default port is 443. This
scheme depends on SSL support in Emacs via the `ssl.el' library and is
actually implemented by forcing the `ssl' gateway method to be used.
*Note Gateways in general::.
-- User Option: url-honor-refresh-requests
This controls honouring of HTTP `Refresh' headers by which servers
can direct clients to reload documents from the same URL or a or
different one. `nil' means they will not be honoured, `t' (the
default) means they will always be honoured, and otherwise the
user will be asked on each request.
* HTTP language/coding::
* HTTP URL Options::
* Dealing with HTTP documents::
File: url, Node: Cookies, Next: HTTP language/coding, Up: http/https
-- User Option: url-cookie-file
The file in which cookies are stored, defaulting to `cookies' in
the directory specified by `url-configuration-directory'.
-- User Option: url-cookie-confirmation
Specifies whether confirmation is require to accept cookies.
-- User Option: url-cookie-multiple-line
Specifies whether to put all cookies for the server on one line in
the HTTP request to satisfy broken servers like
-- User Option: url-cookie-trusted-urls
A list of regular expressions matching URLs from which to accept
-- User Option: url-cookie-untrusted-urls
A list of regular expressions matching URLs from which to reject
-- User Option: url-cookie-save-interval
The number of seconds between automatic saves of cookies to disk.
Default is one hour.
File: url, Node: HTTP language/coding, Next: HTTP URL Options, Prev: Cookies, Up: http/https
3.1.2 Language and Encoding Preferences
HTTP allows clients to express preferences for the language and
encoding of documents which servers may honour. For each of these
variables, the value is a string; it can specify a single choice, or it
can be a comma-separated list.
Normally this list ordered by descending preference. However, each
element can be followed by `;q=PRIORITY' to specify its preference
level, a decimal number from 0 to 1; e.g., for
`url-mime-language-string', `"de, en-gb;q=0.8, en;q=0.7"'. An element
that has no `;q' specification has preference level 1.
-- User Option: url-mime-charset-string
This variable specifies a preference for character sets when
documents can be served in more than one encoding.
HTTP allows specifying a series of MIME charsets which indicate
your preferred character set encodings, e.g., Latin-9 or Big5, and
these can be weighted. The default series is generated
automatically from the associated MIME types of all defined coding
systems, sorted by the coding system priority specified in Emacs.
*Note Recognizing Coding Systems: (emacs)Recognize Coding.
-- User Option: url-mime-language-string
A string specifying the preferred language when servers can serve
files in several languages. Use RFC 1766 abbreviations, e.g.,
`en' for English, `de' for German.
The string can be `"*"' to get the first available language (as
opposed to the default).
File: url, Node: HTTP URL Options, Next: Dealing with HTTP documents, Prev: HTTP language/coding, Up: http/https
3.1.3 HTTP URL Options
HTTP supports an `OPTIONS' method describing things supported by the
-- Function: url-http-options url
Returns a property list describing options available for URL. The
property list members are:
A list of symbols specifying what HTTP methods the resource
A list of numbers specifying what DAV protocol/schema
versions are supported.
A list of supported DASL search types supported (string form).
A list of the units available for use in partial document
The "Platform For Privacy Protection" description for the
resource. Currently this is just the raw header contents.
File: url, Node: Dealing with HTTP documents, Prev: HTTP URL Options, Up: http/https
3.1.4 Dealing with HTTP documents
HTTP URLs are retrieved into a buffer containing the HTTP headers
followed by the body. Since the headers are quasi-MIME, they may be
processed using the MIME library. *Note Emacs MIME: (emacs-mime)Top.
The URL package provides a function to do this in general:
-- Function: url-decode-text-part handle &optional coding
This function decodes charset-encoded text in the current buffer.
In Emacs, the buffer is expected to be unibyte initially and is
set to multibyte after decoding. HANDLE is the MIME handle of the
original part. CODING is an explicit coding to use, overriding
what the MIME headers specify. The coding system used for the
decoding is returned.
Note that this function doesn't deal with `http-equiv' charset
specifications in HTML `<meta>' elements.
File: url, Node: file/ftp, Next: info, Prev: http/https, Up: Supported URL Types
3.2 file and ftp
These schemes are defined in RFC 1808. `ftp:' and `file:' are
synonymous in this library. They allow reading arbitrary files from
hosts. Either `ange-ftp' (Emacs) or `efs' (XEmacs) is used to retrieve
them from remote hosts. Local files are accessed directly.
Compressed files are handled, but support is hard-coded so that
`jka-compr-compression-info-list' and so on have no affect. Suffixes
recognized are `.z', `.gz', `.Z' and `.bz2'.
-- User Option: url-directory-index-file
The filename to look for when indexing a directory, default
`"index.html"'. If this file exists, and is readable, then it
will be viewed instead of using `dired' to view the directory.
File: url, Node: info, Next: mailto, Prev: file/ftp, Up: Supported URL Types
Info URLs are not officially defined. They invoke `Info-goto-node'
with argument `(FILE)NODE'. `#NODE' is optional, defaulting to `Top'.
File: url, Node: mailto, Next: news/nntp/snews, Prev: info, Up: Supported URL Types
A mailto URL will send an email message to the address in the URL, for
example `mailto:fooATbar.com' would compose a message to `fooATbar.com'.
-- User Option: url-mail-command
The function called whenever url needs to send mail. This should
normally be left to default from MAIL-USER-AGENT. *Note
Mail-Composition Methods: (emacs)Mail Methods.
An `X-Url-From' header field containing the URL of the document that
contained the mailto URL is added if that URL is known.
RFC 2368 extends the definition of mailto URLs in RFC 1738. The
form of a mailto URL is
where an arbitrary number of HEADERs can be added. If the HEADER is
`body', then CONTENTS is put in the body otherwise a HEADER header
field is created with CONTENTS as its contents. Note that the URL
library does not consider any headers `dangerous' so you should check
them before sending the message.
Email messages are defined in RFC822.
File: url, Node: news/nntp/snews, Next: rlogin/telnet/tn3270, Prev: mailto, Up: Supported URL Types
3.5 `news', `nntp' and `snews'
The network news URL scheme take the following forms following RFC 1738
except that for compatibility with other clients, host and port fields
may be included in news URLs though they are properly only allowed for
nntp an snews.
Retrieves a list of messages in NEWSGROUP;
Retrieves the message with the given MESSAGE-ID;
Retrieves a list of all available newsgroups;
Similar to the `news' versions.
`:PORT' is optional and defaults to :119.
`snews' is the same as `nntp' except that the default port is :563. (It
is tunneled through SSL.)
An `nntp' URL is the same as a news URL, except that the URL may
specify an article by its number.
-- User Option: url-news-server
This variable can be used to override the default news server.
Usually this will be set by the Gnus package, which is used to
fetch news. It may be set from the conventional environment
File: url, Node: rlogin/telnet/tn3270, Next: irc, Prev: news/nntp/snews, Up: Supported URL Types
3.6 rlogin, telnet and tn3270
These URL schemes from RFC 1738 for logon via a terminal emulator have
but the `:PASSWORD' component is ignored.
To handle rlogin, telnet and tn3270 URLs, a `rlogin', `telnet' or
`tn3270' (the program names and arguments are hardcoded) session is run
in a `terminal-emulator' buffer. Well-known ports are used if the URL
does not specify a port.
File: url, Node: irc, Next: data, Prev: rlogin/telnet/tn3270, Up: Supported URL Types
"Internet Relay Chat" (IRC) is handled by handing off the IRC session
to a function named in `url-irc-function'.
-- User Option: url-irc-function
A function to actually open an IRC connection. This function must
take five arguments, HOST, PORT, CHANNEL, USER and PASSWORD. The
CHANNEL argument specifies the channel to join immediately, this
can be `nil'. By default this is `url-irc-rcirc'.
-- Function: url-irc-rcirc host port channel user password
Processes the arguments and lets `rcirc' handle the session.
-- Function: url-irc-erc host port channel user password
Processes the arguments and lets `ERC' handle the session.
-- Function: url-irc-zenirc host port channel user password
Processes the arguments and lets `zenirc' handle the session.
File: url, Node: data, Next: nfs, Prev: irc, Up: Supported URL Types
Data URLs contain MIME data in the URL itself. They are defined in
MEDIA-TYPE is a MIME `Content-Type' string, possibly including
parameters. It defaults to `text/plain;charset=US-ASCII'. The
`text/plain' can be omitted but the charset parameter supplied. If
`;base64' is present, the DATA are base64-encoded.
File: url, Node: nfs, Next: cid, Prev: data, Up: Supported URL Types
The `nfs:' scheme is defined in RFC 2224. It is similar to `ftp:'
except that it points to a file on a remote host that is handled by the
automounter on the local host.
-- Variable: url-nfs-automounter-directory-spec
A string saying how to invoke the NFS automounter. Certain `%'
sequences are recognized:
The hostname of the NFS server;
The port number of the NFS server;
The username to use to authenticate;
The password to use to authenticate;
The filename on the remote server;
A literal `%'.
Each can be used any number of times.
File: url, Node: cid, Next: about, Prev: nfs, Up: Supported URL Types
File: url, Node: about, Next: ldap, Prev: cid, Up: Supported URL Types
File: url, Node: ldap, Next: imap, Prev: about, Up: Supported URL Types
The LDAP scheme is defined in RFC 2255.
File: url, Node: imap, Next: man, Prev: ldap, Up: Supported URL Types
File: url, Node: man, Prev: imap, Up: Supported URL Types
This is a non-standard scheme. PAGE-SPEC is passed directly to the
Lisp `man' function.
File: url, Node: Defining New URLs, Next: General Facilities, Prev: Supported URL Types, Up: Top
4 Defining New URLs
* Naming conventions::
* Required functions::
* Optional functions::
* Asynchronous fetching::
* Supporting file-name-handlers::
File: url, Node: Naming conventions, Next: Required functions, Up: Defining New URLs
4.1 Naming conventions
File: url, Node: Required functions, Next: Optional functions, Prev: Naming conventions, Up: Defining New URLs
4.2 Required functions
File: url, Node: Optional functions, Next: Asynchronous fetching, Prev: Required functions, Up: Defining New URLs
4.3 Optional functions
File: url, Node: Asynchronous fetching, Next: Supporting file-name-handlers, Prev: Optional functions, Up: Defining New URLs
4.4 Asynchronous fetching
File: url, Node: Supporting file-name-handlers, Prev: Asynchronous fetching, Up: Defining New URLs
4.5 Supporting file-name-handlers
File: url, Node: General Facilities, Next: Customization, Prev: Defining New URLs, Up: Top
5 General Facilities
* Disk Caching::
* Gateways in general::
File: url, Node: Disk Caching, Next: Proxies, Up: General Facilities
5.1 Disk Caching
The disk cache stores retrieved documents locally, whence they can be
retrieved more quickly. When requesting a URL that is in the cache,
the library checks to see if the page has changed since it was last
retrieved from the remote machine. If not, the local copy is used,
saving the transmission over the network. Currently the cache isn't
-- User Option: url-automatic-caching
Setting this variable non-`nil' causes documents to be cached
-- User Option: url-cache-directory
This variable specifies the directory to store the cache files.
It defaults to sub-directory `cache' of
-- User Option: url-cache-creation-function
The cache relies on a scheme for mapping URLs to files in the
cache. This variable names a function which sets the type of
cache to use. It takes a URL as argument and returns the absolute
file name of the corresponding cache file. The two supplied
possibilities are `url-cache-create-filename-using-md5' and
-- Function: url-cache-create-filename-using-md5 url
Creates a cache file name from URL using MD5 hashing. This is
creates entries with very few cache collisions and is fast.
-- Function: url-cache-create-filename-human-readable url
Creates a cache file name from URL more obviously connected to URL
than for `url-cache-create-filename-using-md5', but more likely to
conflict with other files.
File: url, Node: Proxies, Next: Gateways in general, Prev: Disk Caching, Up: General Facilities
5.2 Proxies and Gatewaying
Proxy servers are commonly used to provide gateways through firewalls
or as caches serving some more-or-less local network. Each protocol
(HTTP, FTP, etc.) can have a different gateway server. Proxying is
conventionally configured commonly amongst different programs through
environment variables of the form `PROTOCOL_proxy', where PROTOCOL is
one of the supported network protocols (`http', `ftp' etc.). The
library recognizes such variables in either upper or lower case. Their
values are of one of the forms:
* A full URL;
* Simply a host name.
The `NO_PROXY' environment variable specifies URLs that should be
excluded from proxying (on servers that should be contacted directly).
This should be a comma-separated list of hostnames, domain names, or a
mixture of both. Asterisks can be used as wildcards, but other clients
may not support that. Domain names may be indicated by a leading dot.
says to contact all machines in the `aventail.com' and `seanet.com'
domains directly, as well as the machine named `home.com'. If
`NO_PROXY' isn't defined, `no_PROXY' and `no_proxy' are also tried, in
Proxies may also be specified directly in Lisp.
-- User Option: url-proxy-services
This variable is an alist of URL schemes and proxy servers that
gateway them. The items are of the form
`(SCHEME . HOST:PORTNUMBER)', says that the URL SCHEME is
gatewayed through PORTNUMBER on the specified HOST. An exception
is the pseudo scheme `"no_proxy"', which is paired with a regexp
matching host names not to be proxied. This variable is
initialized from the environment as above.
'(("http" . "proxy.aventail.com:80")
("no_proxy" . "^.*\\(aventail\\|seanet\\)\\.com")))
File: url, Node: Gateways in general, Next: History, Prev: Proxies, Up: General Facilities
5.3 Gateways in General
The library provides a general gateway layer through which all
networking passes. It can both control access to the network and
provide access through gateways in firewalls. This may make direct
connections in some cases and pass through some sort of gateway in
others.(1) The library's basic function responsible for making
connections is `url-open-stream'.
-- Function: url-open-stream name buffer host service
Open a stream to HOST, possibly via a gateway. The other
arguments are as for `open-network-stream'. This will not make a
connection if `url-gateway-unplugged' is non-`nil'.
-- Variable: url-gateway-local-host-regexp
This is a regular expression that matches local hosts that do not
require the use of a gateway. If `nil', all connections are made
through the gateway.
-- Variable: url-gateway-method
This variable controls which gateway method is used. It may be
useful to bind it temporarily in some applications. It has values
taken from a list of symbols. Possible values are:
Use this method if you must first telnet and log into a
gateway host, and then run telnet from that host to connect
to outside machines.
This method is identical to `telnet', but uses `rlogin' to
log into the remote machine without having to send the
username and password over the wire every time.
Use if the firewall has a SOCKS gateway running on it. The
SOCKS v5 protocol is defined in RFC 1928.
This method uses Emacs's builtin networking directly. This
is the default. It can be used only if there is no firewall
The following variables control the gateway methods.
-- User Option: url-gateway-telnet-host
The gateway host to telnet to. Once logged in there, you then
telnet out to the hosts you want to connect to.
-- User Option: url-gateway-telnet-parameters
This should be a list of parameters to pass to the `telnet'
-- User Option: url-gateway-telnet-password-prompt
This is a regular expression that matches the password prompt when
-- User Option: url-gateway-telnet-login-prompt
This is a regular expression that matches the username prompt when
-- User Option: url-gateway-telnet-user-name
The username to log in with.
-- User Option: url-gateway-telnet-password
The password to send when logging in.
-- User Option: url-gateway-prompt-pattern
This is a regular expression that matches the shell prompt.
-- User Option: url-gateway-rlogin-host
Host to `rlogin' to before telnetting out.
-- User Option: url-gateway-rlogin-parameters
Parameters to pass to `rsh'.
-- User Option: url-gateway-rlogin-user-name
User name to use when logging in to the gateway.
-- User Option: url-gateway-prompt-pattern
This is a regular expression that matches the shell prompt.
-- User Option: socks-server
This specifies the default server, it takes the form
`("Default server" SERVER PORT VERSION)' where VERSION can be
either 4 or 5.
-- Variable: socks-password
If this is `nil' then you will be asked for the password,
otherwise it will be used as the password for authenticating you to
the SOCKS server.
-- Variable: socks-username
This is the username to use when authenticating yourself to the
SOCKS server. By default this is your login name.
-- Variable: socks-timeout
This controls how long, in seconds, to wait for responses from the
SOCKS server; it is 5 by default.
-- User Option: socks-nslookup-program
This the `nslookup' program. It is `"nslookup"' by default.
* Suppressing network connections::
---------- Footnotes ----------
(1) Proxies (which only operate over HTTP) are implemented using
File: url, Node: Suppressing network connections, Up: Gateways in general
5.3.1 Suppressing Network Connections
In some circumstances it is desirable to suppress making network
connections. A typical case is when rendering HTML in a mail user
agent, when external URLs should not be activated, particularly to
avoid `bugs' which `call home' by fetch single-pixel images and the
like. To arrange this, bind the following variable for the duration of
-- Variable: url-gateway-unplugged
If this variable is non-`nil' new network connections are never
opened by the URL library.
File: url, Node: History, Prev: Gateways in general, Up: General Facilities
The library can maintain a global history list tracking URLs accessed.
URL completion can be done from it. The history mechanism is set up
automatically via `url-do-setup' when it is configured to be on. Note
that the size of the history list is currently not limited.
The history `list' is actually a hash table,
`url-history-hash-table'. It contains access times keyed by URL
strings. The times are in the format returned by `current-time'.
-- Function: url-history-update-url url time
This function updates the history table with an entry for URL
accessed at the given TIME.
-- User Option: url-history-track
If non-`nil', the library will keep track of all the URLs
accessed. If it is `t', the list is saved to disk at the end of
each Emacs session. The default is `nil'.
-- User Option: url-history-file
The file storing the history list between sessions. It defaults to
`history' in `url-configuration-directory'.
-- User Option: url-history-save-interval
The number of seconds between automatic saves of the history list.
Default is one hour. Note that if you change this variable
directly, rather than using Custom, after `url-do-setup' has been
run, you need to run the function `url-history-setup-save-timer'.
-- Function: url-history-parse-history &optional fname
Parses the history file FNAME (default `url-history-file') and
sets up the history list.
-- Function: url-history-save-history &optional fname
Saves the current history to file FNAME (default
-- Function: url-completion-function string predicate function
You can use this function to do completion of URLs from the
File: url, Node: Customization, Next: GNU Free Documentation License, Prev: General Facilities, Up: Top
6.1 Environment Variables
The following environment variables affect the library's operation at
If this is defined, URL-TEMPORARY-DIRECTORY is initialized from it.
6.2 General User Options
The following user options, settable with Customize, affect the general
operation of the package.
-- User Option: url-debug
Specifies the types of debug messages the library which are logged
to the `*URL-DEBUG*' buffer. `t' means log all messages. A
number means log all messages and show them with `message'. If
may also be a list of the types of messages to be logged.
-- User Option: url-personal-mail-address
-- User Option: url-privacy-level
-- User Option: url-uncompressor-alist
-- User Option: url-passwd-entry-func
-- User Option: url-standalone-mode
-- User Option: url-bad-port-list
-- User Option: url-max-password-attempts
-- User Option: url-temporary-directory
-- User Option: url-show-status
-- User Option: url-confirmation-func
The function to use for asking yes or no functions. This is
normally either `y-or-n-p' or `yes-or-no-p', but could be another
function taking a single argument (the prompt) and returning `t'
only if an affirmative answer is given.
-- User Option: url-gateway-method
A symbol specifying the type of gateway support to use for
connections from the local machine. The supported methods are:
Run telnet in a subprocess to connect;
Rlogin to another machine to connect;
Connect through a socks server;
Connect with SSL;
File: url, Node: GNU Free Documentation License, Next: Function Index, Prev: Customization, Up: Top
Appendix A GNU Free Documentation License
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of "copyleft," which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document," below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you." You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter
section of the Document that deals exclusively with the
relationship of the publishers or authors of the Document to the
Document's overall subject (or to related matters) and contains
nothing that could fall directly within that overall subject.
(Thus, if the Document is in part a textbook of mathematics, a
Secondary Section may not explain any mathematics.) The
relationship could be a matter of historical connection with the
subject or with related matters, or of legal, commercial,
philosophical, ethical or political position regarding them.
The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
the notice that says that the Document is released under this
License. If a section does not fit the above definition of
Secondary then it is not allowed to be designated as Invariant.
The Document may contain zero Invariant Sections. If the Document
does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are
listed, as Front-Cover Texts or Back-Cover Texts, in the notice
that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images
composed of pixels) generic paint programs or (for drawings) some
widely available drawing editor, and that is suitable for input to
text formatters or for automatic translation to a variety of
formats suitable for input to text formatters. A copy made in an
otherwise Transparent file format whose markup, or absence of
markup, has been arranged to thwart or discourage subsequent
modification by readers is not Transparent. An image format is
not Transparent if used for any substantial amount of text. A
copy that is not "Transparent" is called "Opaque."
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
SGML or XML using a publicly available DTD, and
standard-conforming simple HTML, PostScript or PDF designed for
human modification. Examples of transparent image formats include
PNG, XCF and JPG. Opaque formats include proprietary formats that
can be read and edited only by proprietary word processors, SGML
or XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements," "Dedications," "Endorsements," or "History.")
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
applies to the Document are reproduced in all copies, and that you
add no other conditions whatsoever to those of this License. You
may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute. However,
you may accept compensation in exchange for copies. If you
distribute a large enough number of copies you must also follow
the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
and legibly identify you as the publisher of these copies. The
front cover must present the full title with all words of the
title equally prominent and visible. You may add other material
on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a computer-network location from
which the general network-using public has access to download
using public-standard network protocols a complete Transparent
copy of the Document, free of added material. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
copies, to give them a chance to provide you with an updated
version of the Document.
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of previous
versions (which should, if there were any, be listed in the
History section of the Document). You may use the same title
as a previous version if the original publisher of that version
B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in the
Modified Version, together with at least five of the principal
authors of the Document (all of its principal authors, if it
has fewer than five), unless they release you from this
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified Version
under the terms of this License, in the form shown in the
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History," Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on the
Title Page. If there is no section Entitled "History" in the
Document, create one stating the title, year, authors, and
publisher of the Document as given on its Title Page, then add
an item describing the Modified Version as stated in the
J. Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the "History" section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications,"
Preserve the Title of the section, and preserve in the section all
the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements." Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.
You may add a section Entitled "Endorsements," provided it contains
nothing but endorsements of your Modified Version by various
parties-for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition
of a standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements," and any sections Entitled "Dedications." You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the
documents in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
If a section in the Document is Entitled "Acknowledgements,"
"Dedications," or "History," the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided for under this License. Any other
attempt to copy, modify, sublicense or distribute the Document is
void, and will automatically terminate your rights under this
License. However, parties who have received copies, or rights,
from you under this License will not have their licenses
terminated so long as such parties remain in full compliance.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If
the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled ``GNU
Free Documentation License.''
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with the
Front-Cover Texts being LIST, and with the Back-Cover Texts being
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.
File: url, Node: Function Index, Next: Variable Index, Prev: GNU Free Documentation License, Up: Top
Command and Function Index
* Info-goto-node: info. (line 6)
* man: man. (line 6)
* terminal-emulator: rlogin/telnet/tn3270. (line 6)
* url-attributes: Parsed URLs. (line 41)
* url-cache-create-filename-human-readable: Disk Caching. (line 37)
* url-cache-create-filename-using-md5: Disk Caching. (line 31)
* url-completion-function: History. (line 43)
* url-decode-text-part: Dealing with HTTP documents.
* url-do-setup: History. (line 6)
* url-file: Parsed URLs. (line 41)
* url-full: Parsed URLs. (line 41)
* url-generic-parse-url: Parsed URLs. (line 49)
* url-history-parse-history: History. (line 35)
* url-history-save-history: History. (line 39)
* url-history-setup-save-timer: History. (line 29)
* url-history-update-url: History. (line 16)
* url-host: Parsed URLs. (line 41)
* url-http-options: HTTP URL Options. (line 10)
* url-irc-erc: irc. (line 19)
* url-irc-rcirc: irc. (line 16)
* url-irc-zenirc: irc. (line 22)
* url-open-stream: Gateways in general. (line 14)
* url-password: Parsed URLs. (line 41)
* url-port: Parsed URLs. (line 41)
* url-recreate-url: Parsed URLs. (line 52)
* url-retrieve: Retrieving URLs. (line 13)
* url-retrieve-synchronously: Retrieving URLs. (line 7)
* url-set-attributes: Parsed URLs. (line 41)
* url-set-file: Parsed URLs. (line 41)
* url-set-full: Parsed URLs. (line 41)
* url-set-host: Parsed URLs. (line 41)
* url-set-password: Parsed URLs. (line 41)
* url-set-port: Parsed URLs. (line 41)
* url-set-target: Parsed URLs. (line 41)
* url-set-type: Parsed URLs. (line 41)
* url-set-user: Parsed URLs. (line 41)
* url-target: Parsed URLs. (line 41)
* url-type: Parsed URLs. (line 41)
* url-user: Parsed URLs. (line 41)
File: url, Node: Variable Index, Next: Concept Index, Prev: Function Index, Up: Top
* HTTP_PROXY: Proxies. (line 6)
* mail-user-agent: mailto. (line 10)
* NNTPSERVER: news/nntp/snews. (line 36)
* NO_PROXY: Proxies. (line 20)
* socks-nslookup-program: Gateways in general. (line 105)
* socks-password: Gateways in general. (line 92)
* socks-server: Gateways in general. (line 87)
* socks-timeout: Gateways in general. (line 101)
* socks-username: Gateways in general. (line 97)
* TMPDIR: Customization. (line 13)
* url-automatic-caching: Disk Caching. (line 14)
* url-bad-port-list: Customization. (line 38)
* url-cache-creation-function: Disk Caching. (line 23)
* url-cache-directory: Disk Caching. (line 18)
* url-configuration-directory: Configuration. (line 7)
* url-confirmation-func: Customization. (line 46)
* url-cookie-confirmation: Cookies. (line 11)
* url-cookie-file: Cookies. (line 7)
* url-cookie-multiple-line: Cookies. (line 14)
* url-cookie-save-interval: Cookies. (line 27)
* url-cookie-trusted-urls: Cookies. (line 19)
* url-cookie-untrusted-urls: Cookies. (line 23)
* url-debug: Customization. (line 22)
* url-directory-index-file: file/ftp. (line 19)
* url-gateway-local-host-regexp: Gateways in general. (line 19)
* url-gateway-method <1>: Customization. (line 52)
* url-gateway-method: Gateways in general. (line 24)
* url-gateway-prompt-pattern: Gateways in general. (line 72)
* url-gateway-rlogin-host: Gateways in general. (line 75)
* url-gateway-rlogin-parameters: Gateways in general. (line 78)
* url-gateway-rlogin-user-name: Gateways in general. (line 81)
* url-gateway-telnet-host: Gateways in general. (line 50)
* url-gateway-telnet-login-prompt: Gateways in general. (line 62)
* url-gateway-telnet-parameters: Gateways in general. (line 54)
* url-gateway-telnet-password: Gateways in general. (line 69)
* url-gateway-telnet-password-prompt: Gateways in general. (line 58)
* url-gateway-telnet-user-name: Gateways in general. (line 66)
* url-gateway-unplugged: Suppressing network connections.
* url-history-file: History. (line 25)
* url-history-hash-table: History. (line 11)
* url-history-save-interval: History. (line 29)
* url-history-track: History. (line 20)
* url-honor-refresh-requests: http/https. (line 19)
* url-irc-function: irc. (line 10)
* url-mail-command: mailto. (line 10)
* url-max-password-attempts: Customization. (line 40)
* url-mime-charset-string: HTTP language/coding.
* url-mime-language-string: HTTP language/coding.
* url-news-server: news/nntp/snews. (line 34)
* url-nfs-automounter-directory-spec: nfs. (line 13)
* url-passwd-entry-func: Customization. (line 34)
* url-personal-mail-address: Customization. (line 28)
* url-privacy-level: Customization. (line 30)
* url-proxy-services: Proxies. (line 35)
* url-show-status: Customization. (line 44)
* url-standalone-mode: Customization. (line 36)
* url-temporary-directory: Customization. (line 13)
* url-uncompressor-alist: Customization. (line 32)
File: url, Node: Concept Index, Prev: Variable Index, Up: Top
* automounter: nfs. (line 6)
* bugs, HTML: Suppressing network connections.
* Cache cleaning: Disk Caching. (line 10)
* Caching: Disk Caching. (line 6)
* character sets: HTTP language/coding.
* Cleaning the cache: Disk Caching. (line 10)
* Clearing the cache: Disk Caching. (line 10)
* coding systems: HTTP language/coding.
* compressed files: file/ftp. (line 6)
* configuration files: Configuration. (line 7)
* Content-ID: cid. (line 6)
* DASL: HTTP URL Options. (line 22)
* data URLs: data. (line 6)
* DAV: HTTP URL Options. (line 18)
* debugging: Customization. (line 22)
* dired: file/ftp. (line 6)
* Disk Cache: Disk Caching. (line 6)
* email: mailto. (line 6)
* environment variable: news/nntp/snews. (line 36)
* environment variables <1>: Customization. (line 9)
* environment variables: Proxies. (line 6)
* ERC: irc. (line 6)
* File Transfer Protocol: file/ftp. (line 6)
* files: file/ftp. (line 6)
* firewalls: Gateways in general. (line 6)
* FTP: file/ftp. (line 6)
* gateways: Gateways in general. (line 6)
* HTML `bugs': Suppressing network connections.
* IMAP: imap. (line 6)
* Info: info. (line 6)
* Internet Relay Chat: irc. (line 6)
* IRC: irc. (line 6)
* language preferences: HTTP language/coding.
* LDAP: ldap. (line 6)
* Lightweight Directory Access Protocol: ldap. (line 6)
* mailto: mailto. (line 6)
* man: man. (line 6)
* MD5: Disk Caching. (line 32)
* network connections, suppressing: Suppressing network connections.
* Network File System: nfs. (line 6)
* network news: news/nntp/snews. (line 6)
* news: news/nntp/snews. (line 6)
* NFS: nfs. (line 6)
* NNTP: news/nntp/snews. (line 6)
* nslookup: Gateways in general. (line 105)
* opening a stream: Gateways in general. (line 14)
* P3P: HTTP URL Options. (line 29)
* parsed URLs: Parsed URLs. (line 6)
* Persistent Cache: Disk Caching. (line 6)
* proxies: Proxies. (line 6)
* proxy servers: Proxies. (line 6)
* rcirc: irc. (line 6)
* rlogin <1>: Gateways in general. (line 34)
* rlogin: rlogin/telnet/tn3270.
* snews: news/nntp/snews. (line 6)
* SOCKS: Gateways in general. (line 39)
* SSL: news/nntp/snews. (line 27)
* stream, opening: Gateways in general. (line 14)
* suppressing network connections: Suppressing network connections.
* telnet <1>: Gateways in general. (line 29)
* telnet: rlogin/telnet/tn3270.
* terminal emulation: rlogin/telnet/tn3270.
* Texinfo: info. (line 6)
* tn3270: rlogin/telnet/tn3270.
* Unix man pages: man. (line 6)
* unparsing URLs: Parsed URLs. (line 52)
* URIs: Getting Started. (line 6)
* URLs, definition: Getting Started. (line 6)
* usenet: news/nntp/snews. (line 6)
* ZEN IRC: irc. (line 6)
* ~/.url: Configuration. (line 7)