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|
<!-- $LynxId: lynx_url_support.html,v 1.36 2017/04/28 16:47:05 tom Exp $ -->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html>
<head>
<meta name="generator" content=
"HTML Tidy for Linux (vers 25 March 2009), see www.w3.org">
<title>URL Schemes Supported in Lynx</title>
<link rev="made" href="mailto:lynx-dev@nongnu.org">
<meta http-equiv="Content-Type" content=
"text/html; charset=us-ascii">
<meta name="description" content=
" Enumerate, describe and provide examples of Lynx's URL support on Unix and VMS. Lynx supports both Web standards and extensions.">
</head>
<body>
<blockquote>
<p><em>[</em><a href="#http_url">http, https</a> <em>|</em>
<a href="#telnet_url">telnet, tn3270, rlogin</a> <em>|</em>
<a href="#gopher_url">gopher</a> <em>|</em> <a href=
"#file_url">file</a> <em>|</em> <a href="#ftp_url">ftp</a>
<em>|</em> <a href="#wais_url">wais</a> <em>|</em> <a href=
"#news_url">news, nntp, snews</a> <em>|</em> <a href=
"#newspost_url">newspost, newsreply, snewspost, snewsreply</a>
<em>|</em> <a href="#mailto_url">mailto</a> <em>|</em> <a href=
"#finger_url">finger</a> <em>|</em> <a href="#cso_url">cso</a>
<em>|</em> <a href="#bibp_url">bibp</a> <em>|</em> <a href=
"#exec_url">lynxexec, lynxprog</a> <em>|</em> <a href=
"#cgi_url">lynxcgi</a><em>|</em> <a href="#ncftp_url">NcFTP</a>
<em>|</em> <a href="#internal_url">internal</a><em>]</em></p>
</blockquote>
<h1><em>URL Schemes Supported in Lynx</em></h1>
<p><strong>Lynx</strong> handles a number of URL types, that are
enumerated below. For more details about URLs (Uniform Resource
Locators) see <em>RFC1738</em>:</p>
<ul>
<li><a href=
"http://www.w3.org/Addressing/rfc1738.txt">http://www.w3.org/Addressing/rfc1738.txt</a></li>
<li><a href=
"ftp://ftp.rfc-editor.org/in-notes/rfc1738.txt">ftp://ftp.rfc-editor.org/in-notes/rfc1738.txt</a></li>
</ul>
<p><strong>Lynx</strong> resolves partial or relative URLs in
documents with respect to the BASE if one was specified,
otherwise with respect to the document's absolute URL, using the
rules described in <em>RFC1808</em>:</p>
<ul>
<li><a href=
"http://www.w3.org/Addressing/rfc1808.txt">http://www.w3.org/Addressing/rfc1808.txt</a></li>
<li><a href=
"ftp://ftp.rfc-editor.org/in-notes/rfc1808.txt">ftp://ftp.rfc-editor.org/in-notes/rfc1808.txt</a></li>
</ul>
<p>and in subsequent drafts of the <em>IETF</em>:</p>
<ul>
<li><a href=
"https://web.archive.org/web/20130116065936/http://ftp.ics.uci.edu/pub/ietf/uri/">
Uniform Resource Identifiers (URI) Working Group</a></li>
</ul>
<p>When entering a URL on the command line to be used as the
<em>startfile</em>, or at the prompt for a
“<em>g</em>”oto entry, a partial host field can be
used and the scheme field can be omitted if the scheme and fully
qualified domain name can be constructed internally by using the
URL_DOMAIN_PREFIXES and URL_DOMAIN_SUFFIXES definitions in the
<strong>Lynx</strong> configuration file. See the explanation of
those definitions and their use in your <em>lynx.cfg</em>.</p>
<p>For example, <em>wfbr</em> will be treated as
<em>http://www.wfbr.edu/</em>, and <em>wfbr/dir/lynx</em> will be
treated as <em>http://www.wfbr.edu/dir/lynx</em>, but
<em>gopher.wfbr.edu/11/_fileserv/_lynx</em> will be treated as
<em>gopher://gopher.wfbr.edu/11/_fileserv/_lynx</em>.</p>
<p>For files or directories on the local host, a tilde
(<em>~</em>) is expanded to the path of the account's login
directory, e.g., <em>~/foo</em> will be expanded to
<em>file://localhost/your/login/directory/foo</em>. The tilde
expansion is done homologously on Unix and VMS.</p>
<p>On VMS, <strong>Lynx</strong> also will expand any file or
directory spec recognizable to DCL into a valid URL, e.g.,
<em>[]</em> will be expanded to
<em>file://localhost/current/default/directory</em>.</p>
<p>These expansions are <em>SOLELY</em> for <em>startfile</em> or
“<em>g</em>”oto entries! Any partial or relative URLs
within HTML documents are resolved according to the rules
specified in RFC1808 and subsequent IETF drafts.</p>
<hr>
<h2><a name="http_url" id="http_url">The <em>http</em> and
<em>https</em> URLs:</a></h2>
<p><strong>Lynx</strong> handles http URLs exactly as specified
in RFC1738. The format is:</p>
<pre>
<em>http://host:port/path?searchpart#fragment</em>
</pre>
<p>where <em>:port</em> is optional and defaults to <em>:80</em>,
<em>/path</em> if present is a slash-separated series of symbolic
elements, and <em>?searchpart</em> if present is the query for an
ISINDEX search or the content of a FORM with METHOD="GET". The
<em>#fragment</em> field if present indicates a location in the
document to seek for display, based on a NAME-ed anchor or an ID
attribute within the document, and is technically an instruction
rather than part of the URL. <strong>Lynx</strong> will treat ID
attributes as NAME-ed anchors for all tags in the BODY of a
document which can correspond to positions in the rendering of
the document.</p>
<p>The https URL has the same format, but the default port is
<em>:443</em>.</p>
<p><strong>Lynx</strong> relies for https support on external
libraries (OpenSSL or GnuTLS) whose capabilities have evolved
over time. In turn, those libraries may depend upon external
resources for verifying SSL certificates. For instance,
certification revocation may be provided via the Online
Certificate Status Protocol (OCSP) which is an external service.
Without this facility, <strong>Lynx</strong> may not warn about
websites using revoked SSL certificates.</p>
<hr>
<h2><a name="telnet_url" id="telnet_url">The <em>telnet</em>,
<em>tn3270</em>, and <em>rlogin</em> URLs:</a></h2>
<p>A <em>telnet</em> URL generally results in
<strong>Lynx</strong> spawning a telnet session.
<strong>Lynx</strong> implements the complete telnet URL scheme,
i.e.:</p>
<pre>
<em>telnet://user:password@host:port</em>
</pre>
<p>The <em>user</em> and/or <em>:password</em> fields may be
omitted, and the <em>@</em> should be omitted if neither is
present. The port defaults to <em>:23</em> when omitted in the
URL.</p>
<p>A <em>tn3270</em> or <em>rlogin</em> URL is specified
equivalently, and similarly spawns a tn3270 or rlogin session.
The actual behavior is dependent on the TCP-IP software installed
on the local and target hosts.</p>
<p>It is unwise to include the <em>:password</em> field except
for URLs which point to anonymous or other public access
accounts, and for most TCP-IP software you will be prompted for a
password whether or not one was included in the URL.</p>
<hr>
<h2><a name="gopher_url" id="gopher_url">The <em>gopher</em>
URL:</a></h2>
<p>The gopher URL takes the form:</p>
<pre>
<em>gopher://host:port/gopher-path</em>
</pre>
<p>where <em>:port</em> is optional and defaults to <em>:70</em>,
and the <em>/gopher-path</em> is opaque (not fully equivalent to
the slash-separated series of symbolic elements of http paths) as
explained in RFC1738. Typically, the gopher-path consists of a
<a href=
"keystrokes/gopher_types_help.html"><em>gophertype</em></a>
indicating the file or service type (e.g., <em>0</em> or
<em>I</em> for plain text or an image, respectively, <em>7</em>
for a search, or <em>1</em> for a directory), followed by a
platform-specific <em>selector</em>. Any reserved characters in
the selector should be hex escaped (<em>%hh</em>), including
slashes, although hex escaping of slashes is not required by
<strong>Lynx</strong> in gopher URLs.</p>
<p><strong>Lynx</strong> does not overtly support the gopher+
protocol, and does not represent itself as gopher+ capable when
communicating with gopher servers. <strong>Lynx</strong> might
transmit any (hex-escaped-tab-separated) extended gopher+ fields
in a URL if an author included them in a document, but is likely
to mishandle what the gopher server returns in such cases, and
would not generate and transmit them itself. For pre-formed URLs
to submit gopher searches, it may be better to use a <em>?</em>
rather than hex-escaped tab (<em>%09</em>) as the separator for
the <em>searchpart</em> in the <em>selector</em>, e.g.:<br>
<em>gopher://gopher.wfbr.edu/77/_shell/search.shell%20/_shell/walker?lynx*</em>
<strong>Lynx</strong> will handle the <em>%09</em> if you use
that instead of <em>?</em>, but other WWW clients may mishandle
it.</p>
<p>For the <em>gophertype</em> which signifies HTML (<em>h</em>),
if the <em>selector</em> begins with <em>GET%20/</em>
<strong>Lynx</strong> will convert the gopher URL to an http URL,
e.g.:<br></p>
<pre>
<em>gopher://www.wfbr.edu:80/hGET%20/</em>
</pre>
<p>will become:<br></p>
<pre>
<em>http://www.wfbr.edu/</em>
</pre>
<p>The port field will be retained if it is not <em>:80</em>, and
will default to <em>:70</em> if it was defaulted originally.
These conventions were adopted during development of the
University of Minnesota gopher software to facilitate the
offering of links to MIME-capable http servers in the listings
returned by gopher servers, but should be considered Lynxisms and
UMN Gopherisms.</p>
<hr>
<h2><a name="file_url" id="file_url">The <em>file</em>
URL:</a></h2>
<p>The file URL is used to retrieve files or generate a directory
listing on the local host. The host field can be
<em>localhost</em> or a domain name for the local host:<br></p>
<pre>
<em>file://localhost/path</em>
</pre>
<p>If you do not use <em>localhost</em> or a domain name for the
local host, <strong>Lynx</strong> will substitute <em>ftp://</em>
for <em>file://</em> and treat it as an ftp URL.</p>
<p>The <em>/path</em> is treated as originating at the root,
unless you include a tilde (<em>~</em>), e.g.:</p>
<pre>
<em>file://localhost/~/foo</em> will be converted to:
<em>file://localhost/your/login/directory/foo</em>
</pre>
<p>The latter feature is a Lynxism, is done homologously on Unix
and VMS, and should be used ONLY in local documents intended for
<strong>Lynx</strong>.</p>
<p>On VMS, the first element of the path, if not a tilde, is
assumed to be a device, e.g.:</p>
<pre>
<em>file://localhost/www_root/directory/filename.suffix</em>
</pre>
<p>should be used for:
<em>www_root:[directory]filename.suffix</em><br>
If you are unsure how to specify a file URL in local documents on
VMS, invoke <strong>Lynx</strong> with the desired file or
directory as the <em>startfile</em> using any spec acceptable to
DCL, and then use the <em>showinfo</em> command (<em>=</em>) to
see the file URL which <strong>Lynx</strong> created for it.</p>
<hr>
<h2><a name="ftp_url" id="ftp_url">The <em>ftp</em> URL:</a></h2>
<p>The ftp URL has the general format:</p>
<pre>
<em>ftp://host:port/path;type=[D,I, or A]</em>
<em>ftp://username@host:port/path;type=[D,I, or A]</em>
</pre>
<p>The default port is <em>:21</em> and the default
<em>username</em> is <em>anonymous</em>. If <em>username</em> is
included, <strong>Lynx</strong> will prompt you for the password.
For anonymous ftp, <strong>Lynx</strong> uses your
<em>personal_mail_address</em> (user@host) as the
<em>password</em> if it has been defined via the
“<em>o</em>”ptions menu. Otherwise,
<strong>Lynx</strong> uses the dummy password <em>WWWUser</em>.
(A password can also be embedded in the URL, by replacing
<em>username</em> with <em>username:password</em>. This is
strongly discouraged for “real” passwords that must
be kept secret, since URLs with the completely unencrypted
<em>password</em> may show up on the screen, in HISTORY and LIST
pages etc., and may even become visible to remote sites for
example through Referer headers.) Do not include the <em>@</em>
if neither <em>username</em> nor <em>:password</em> is
included.</p>
<p>The <em>;type=</em> parameter can be used with value
<em>D</em>, <em>I</em>, or <em>A</em> to force handling of the
URL as, respectively, a directory listing, binary file, or ASCII
file. The <strong>Lynx</strong> ftp gateway normally determines
this itself, but the parameter can be used if the internal
procedure draws an incorrect inference about the nature of the
ftp URL.</p>
<p>The <em>/path</em> is treated according to RFC1738 for VMS and
VM/CMS ftp servers. The lead slash (<em>/</em>) is treated purely
as a separator, not as a designator for the root, and the
<em>path</em> string if present is treated as in or under the
login directory. For VMS ftp servers, if you wish to have the
first element treated as a device rather than file or
subdirectory name, begin it with a hex-escaped slash
(<em>%2f</em>), e.g.:</p>
<pre>
<em>ftp://user@myhost/%2fsys$common/syshlp</em>
</pre>
<p>can be used for a listing of sys$common:[syshlp]<br>
Also, on VM/CMS ftp servers, if the <em>path</em> string begins
with <em>vmsysu%3a</em> it receives special handling as an SFS
path, e.g.:</p>
<pre>
<em>ftp://ubvm.cc.buffalo.edu/vmsysu%3alistserv.webshare</em>
</pre>
<p>For Unix and Unix-emulation ftp servers, RFC1738 is not
respected and the lead slash is treated as the root, i.e., the
<em>/path</em> is handled equivalently to that in file URLs. The
distinction is irrelevant for anonymous ftp, but matters when
using ftp for non-anonymous accounts. If you are using ftp with a
Unix server and do wish to get a listing of the login directory
or have the <em>path</em> string treated as a file or path under
the login directory, include a tilde (<em>~</em>) as for <a href=
"#file_url">file</a> URLs, e.g.:</p>
<pre>
<em>ftp://user@myhost/~</em>
</pre>
<hr>
<h2><a name="wais_url" id="wais_url">The <em>wais</em>
URL:</a></h2>
<p>The wais URL is used to retrieve resources using the Wide Area
Information System protocol. The format is:</p>
<pre>
<em>wais://host:port/database</em>
<em>wais://host:port/database?wais_query</em>
<em>wais://host:port/database/wais_type/wais_path</em>
</pre>
<p>where <em>:port</em> defaults to <em>:210</em></p>
<p>Direct wais support is built into <strong>Lynx</strong> for
VMS, and can be compiled into <strong>Lynx</strong> on Unix.</p>
<p>If only a <em>database</em> is indicated in the URL,
<strong>Lynx</strong> returns an ISINDEX cover page for searching
that <em>database</em>, and will submit your search with the
<em>wais_query</em> appended. <strong>Lynx</strong> will convert
the server's reply into a hit list with URLs that include the
<em>wais_type</em> and <em>wais_path</em> for retrieving items
from the hit list.</p>
<hr>
<h2><a name="news_url" id="news_url">The <em>news</em>,
<em>nntp</em>, and <em>snews</em> URLs:</a></h2>
<p>The news and nntp URLs are handled by <strong>Lynx</strong> as
specified in RFC1738, but for compatibility with other clients,
<strong>Lynx</strong> allows inclusion of host and port fields in
news URLs, which properly should be used <em>only</em> in nntp
and snews URLs. If not included in news URLs,
<strong>Lynx</strong> will use the nntp server pointed to by the
NNTPSERVER environment variable or configuration symbol (see
lynx.cfg), with default port <em>:119</em>. A host field must be
included in nntp URLs, and the port field is optional with the
same default.</p>
<p>If the URL requires authentication, <strong>Lynx</strong> will
prompt you for the username and password. These are cached during
a session, for reuse on the same host. If $HOME/.newsauth exists,
<strong>Lynx</strong> initializes its cache from this file. The
.newsauth file contents are one line per entry: hostname,
password and username (in that order) separated by a space.</p>
<p>The formats are:<br></p>
<pre>
<em>news:newsgroup</em> (retrieves list of messages in newsgroup)
<em>news:messageID</em> (retrieves the message)
<em>news:*</em> (retrieves list of all available newsgroups)
<em>nntp://host:port/newsgroup</em>
<em>nntp://host:port/messageID</em>
<em>nntp://host:port/*</em>
</pre>
<p>(snews same as nntp, but the default port is
<em>:563</em>)</p>
<p>The <em>messageID</em> is the message's unique identifier,
consisting of an identification string and the host of origin for
the message (<em>ident_string@origin_host</em>).</p>
<p><strong>Lynx</strong> also supports wildcarding via an
asterisk for listings of news hierarchies or sub-hierarchies,
e.g.:</p>
<pre>
<em>news:comp.infosystems.*</em>
<em>nntp://host:port/comp.infosystems.*</em>
</pre>
<p>(snews same as nntp, but the default port is
<em>:563</em>)<br>
This is not in RFC1738 and may not be supported by all other
clients.</p>
<p><strong>Lynx</strong> allows you both to <em>reply</em> to the
author of a news message via email, and, if news posting has been
enabled, to send a <em>followup</em> message to the newsgroup
(see <a href="#newspost_url">newspost, newsreply, snewspost,
snewsreply</a>).</p>
<p><strong>Lynx</strong> converts any strings in news messages
which appear to be a URL with a supported scheme into a link for
accessing that URL.</p>
<p><strong>Lynx</strong> also supports the newsgroup and message
number URL scheme:<br></p>
<pre>
<em>news:newsgroup/startNo-endNo</em> (lists message range in newsgroup)
<em>news:newsgroup/messageNo</em> (retrieves the message by number)
<em>nntp://host:port/newsgroup/startNo-endNo</em>
<em>nntp://host:port/newsgroup/messageNo</em>
</pre>
<p>(snews same as nntp, but the default port is
<em>:563</em>)<br>
Use of this scheme is not recommended, because the message
numbers are specific to each nntp server, unlike the unique
identifiers for news messages.</p>
<hr>
<h2><a name="newspost_url" id="newspost_url">The
<em>newspost</em>, <em>newsreply</em>, <em>snewspost</em>, and
<em>snewsreply</em> URLs:</a></h2>
<p>When <strong>Lynx</strong> receives group listings or articles
via <em>news</em>, <em>nntp</em> or <em>snews</em> URLs, it also
checks whether the nntp server supports posting from the
<strong>Lynx</strong> user's site, and if so, includes links for
posting new messages to that server, or for posting followups
(replies) to previously posted messages. RFC1738, and IETF URL
drafts through this release of <strong>Lynx</strong>, do not
include any schemes for posting to news groups.
<strong>Lynx</strong> has long supported newspost and newreply
URL schemes for posting new messages or sending followups,
respectively, to standard nntp servers, with default port
<em>:119</em>. <strong>Lynx</strong> now also supports homologous
snewspost and snewsreply URLs for use with SSL capable nntp
servers.</p>
<p>The formats are:</p>
<pre>
<em>newspost://host:port/newsgroup(s)</em> (post a new message)
<em>newsreply://host:port/newsgroup(s)</em> (post a followup message)
</pre>
<p>(snewspost and snewsreply have the same formats, but the
default port is <em>:563</em>)</p>
<p>If the host field is omitted, it defaults to that pointed to
by the NNTPSERVER configuration or environmental variable.
Inclusion of at least one newsgroup in the URL is required, and
additional groups can be specified as a comma-separated list.
Wildcarding of newsgroup names is not supported for these URLs.
For newsreply and snewsreply URLs, if an external editor has been
defined via the <em>Options Menu</em>, the user is offered an
option to include the currently displayed document, which
presumably is a news article with a <em>followup</em> link that
was activated, and if confirmed, each line of that document is
prefixed with a right-angle-bracket. The user is expected to edit
such an inclusion so that only the passages relevant to the
followup message are retained.</p>
<p>These URLs can be used as command line startfiles (in which
case, <strong>Lynx</strong> will exit after posting the message,
and the newreply or snewsreply URLs degrade to newspost or
snewpost URLs, respectively). They also can be used as HREF
attribute values in any HTML document homologously to <a href=
"#mailto_url">mailto</a> URLs, with the qualification that they
presently are supported only by <strong>Lynx</strong>.</p>
<hr>
<h2><a name="mailto_url" id="mailto_url">The <em>mailto</em>
URL:</a></h2>
<p>The mailto URL is used to provide links that when activated
can be used to send a comment or the content of a FORM to an
Internet email address (user@host). The format is:</p>
<pre>
<em>mailto:user@host</em>
</pre>
<p>The description of the mailto URL in RFC1738 has been
interpreted by some as allowing only a single recipient, but
<strong>Lynx</strong> invented the mailto URL, has always
supported a series of user@host addresses as a comma-separated
list, and still does. For compatibility with Explorer,
<strong>Lynx</strong> also accepts a semi-colon-separated
list.</p>
<p>For compatibility with Netscape, <strong>Lynx</strong> parses
any <em>?subject=The%20Subject</em> appended to the URL, trims
the URL at the <em>?</em>, and uses the value as the default
Subject: for the message or FORM content mailing. This is not
recommended practice. The preferred way to indicate the default
Subject: for a LINK or Anchor with a mailto HREF, or a FORM with
a mailto ACTION, is via a TITLE attribute with the subject string
as its value, e.g.:</p>
<pre>
<em><LINK REV="made"
HREF="mailto:me@myhost,her@herhost" TITLE="The Subject"></em>
<em><A HREF="mailto:user@host" TITLE="The Subject">...</A></em>
<em><FORM METHOD="post" ENCTYPE="text/plain"
ACTION="mailto:WebMaster@host" TITLE="The Subject">
...
</FORM></em>
</pre>
<p>Note that a TITLE attribute for FORM is now included in the
HTML specifications. Some clients use a SUBJECT attribute for
this purpose in FORM tags, and <strong>Lynx</strong> recognizes
that as a synonym for TITLE.</p>
<p><strong>Lynx</strong> also will process any
<em>to=address(es)</em>, <em>cc=address(es)</em>,
<em>keywords=word_list</em> and/or <em>body=message</em> fields
in <em>?searchpart</em> tack-ons to mailto URLs. The <em>to</em>
and/or <em>cc</em> values can be single addresses, or comma- or
semi-colon-separated lists of addresses. All addresses, and any
<em>body</em> values, will be offered for approval by the user
before proceeding with a mailing. Any other name=value pairs in
the <em>?searchpart</em> will be ignored. Also, if the mailto URL
is the ACTION for a FORM, any <em>body</em> in a
<em>?searchpart</em> tack-on will be ignored, because the body of
the mailing must be constructed solely from the the FORM's
content. <strong>Lynx</strong> expects multiple name=value pairs
in a <em>?searchpart</em> tack-on to be separated by ampersands,
as in the original Netscape implementation, and in an equally
ill-advised IETF draft of that implementation (<a href=
"ftp://ftp.isi.edu/internet-drafts/draft-hoffman-mailto-url-03.txt">draft-hoffman-mailto-url-03.txt</a>).
These should be represented as entities (<em>&amp;</em>) in
the HTML markup. This functionality is generally desired, but the
IETF backward compatibility principal normally would lead to a
new scheme being used (e.g., <em>mail:</em>, or <em>smtp:</em>),
rather than breaking <em>mailto:</em> implementations.</p>
<p>If <em>ENCTYPE="text/plain"</em> is specified for a FORM with
a mailto ACTION, <strong>Lynx</strong> will not hex escape the
name=value pairs of the FORM's content, and will use physical
newlines instead of “<em>&</em>” or
“<em>;</em>” to separate the pairs, so that the
content will be readable directly. Otherwise,
<strong>Lynx</strong> will mail the content with the default:</p>
<pre>
<em>ENCTYPE="application/x-www-form-urlencoded"</em> (“<em>&</em>” separates pairs)
</pre>
<p>or:</p>
<pre>
<em>ENCTYPE="application/sgml-form-urlencoded"</em> (“<em>;</em>” separates pairs)
</pre>
<p>if the latter was indicated.</p>
<p>Note that when mailing FORM content <strong>Lynx</strong>
wraps any lines longer than 78 characters, to avoid buffer
overflows in mail software and to ensure reliable transmission
across gateways. If the ENCTYPE was not <em>text/plain</em>, any
script which decodes the mailed content should ignore the
physical newlines and recognize only hex escaped newline
characters as intended to be present in the decoded content.</p>
<p>If the mailto URL is not the ACTION for a FORM, and if an
external editor has been defined via the <em>Options Menu</em>,
the user is offered an option to include the currently displayed
document. If this option is accepted, each line of that document
is prefixed with a right-angle-bracket, and the prefixed
inclusion should be trimmed by the user to just those passages
relevant to the message which will be sent.</p>
<hr>
<h2><a name="finger_url" id="finger_url">The <em>finger</em>
URL:</a></h2>
<p><strong>Lynx</strong> has full support for the finger
protocol, but a format for finger URLs has not yet been adopted
by the IETF. The formats supported by <strong>Lynx</strong>
therefore include every possibility not inconsistent with
RFC1738, including:</p>
<pre>
finger://host finger://@host
finger://host/ finger://@host/
finger://host/%2fw finger://@host/w
finger://host/w finger://host/w/
finger://host/username[@host] finger://username@host
finger://host/username[@host]/ finger://username@host/
finger://host/w/username[@host] finger://username@host/w
finger://host/%2fw%20username[@host] finger://host/username[@host]/w
finger://host/w/username
</pre>
<p>Activating a finger URL will send a request to the finger
server via port 79 on the host specified. You can include
<em>:79</em> in the URL, but no other value is allowed. The
<em>/w</em> or <em>/%2fw</em> is used to request a full report
for finger servers which support it, and is not case sensitive
(i.e., can be <em>/W</em> or <em>/%2fW</em>). Any strings in the
report which appear to be a URL with a supported scheme will be
converted into a link for accessing that URL.</p>
<p>An alternative way to access finger servers is via gopher URLs
with port 79 and the plain text (<em>0</em>) <em>gophertype</em>
specified:<br>
<em>gopher://host:79/0</em><br>
<strong>Lynx</strong> will handle such URLs equivalently to overt
finger URLs, including creation of links for any strings which
appear to be supported URLs.</p>
<hr>
<h2><a name="cso_url" id="cso_url">The <em>cso</em> URL:</a></h2>
<p>The cso URL is intended to provide a gateway to CSO/PH (QI)
servers. The requests are made on port 105 by default
(<em>:105</em>), with the following overt cso URL format:<br></p>
<pre>
<em>cso://host</em>
</pre>
<p>You also can use a gopher URL format with port 105 and the CSO
(<em>2</em>) <em>gophertype</em> specified:</p>
<pre>
<em>gopher://host:105/2</em>
</pre>
<p><strong>Lynx</strong> will parse the stream returned by the
server for the above URLs and create a FORM for submitting
additional requests (searches) to the server. Any strings in the
reports returned for these requests (searches) which appear to be
a URL with a supported scheme will be converted into a link for
accessing that URL.</p>
<hr>
<h2><a name="bibp_url" id="bibp_url">The <em>bibp</em>
URL:</a></h2>
<p><strong>Lynx</strong> provides built-in support for
bibliographic protocol (BibP). BibP links are links to published
works such as books or journal articles, without a predefined
server. BibP links are intended for resolution by a local bibhost
server (http://bibhost/) if it exists. Otherwise, resolution is
performed by a document-specified server or a known global
server.</p>
<h2><a name="exec_url" id="exec_url">The <em>lynxexec</em> and
<em>lynxprog</em> URLs:</a></h2>
<p>If execution of spawned commands has been enabled in your
<strong>Lynx</strong> image, the lynxexec and lynxprog URLs can
be used to execute arbitrary system commands or invoke system
utilities. Any system command and associated switches or
qualifiers can be used, with the syntax appropriate for a shell
running <strong>Lynx</strong> on Unix, or for DCL on VMS,
e.g.:</p>
<pre>
<em>lynxexec:dir/date/size foo:[blah]</em> (VMS)
<em>lynxexec:ls -l /foo/blah</em> (Unix)
<em>lynxprog:news</em>
</pre>
<p>(Note, however, that restrictions on acceptable commands or
utilities may be imposed by the system administrator.)</p>
<p>You optionally can include <em>//localhost/</em> in the URL,
between the scheme field and the command, but that is always
implied. The lynxexec and lynxprog URLs differ only in that with
lynxexec you are prompted to enter <em>RETURN</em> before
<strong>Lynx</strong> clears the screen and restores the
previously displayed document, so that you can read any screen
output generated by the spawned command, whereas no such pause is
imposed upon exit from the utility invoked via lynxprog.</p>
<p>These are Lynxisms and should be used only in local documents
intended solely for <strong>Lynx</strong>.</p>
<hr>
<h2><a name="cgi_url" id="cgi_url">The <em>lynxcgi</em>
URL:</a></h2>
<p>The lynxcgi URL is implemented only on Unix, can be used as
the ACTION for a FORM, and if enabled in your
<strong>Lynx</strong> image has the format:</p>
<pre>
<em>lynxcgi://localhost/path_to_CGI_script</em>
</pre>
<p>where <em>//localhost</em> is optional and always implied; the
full path should be specified, as “~” is not
recognized; if the script is in the directory
<strong>Lynx</strong> was started from, the simple file name is
adequate. The output of the script should be text/html and is
rendered and displayed by <strong>Lynx</strong>. Restrictions on
use of lynxcgi and on acceptable paths can be imposed in
<em>userdefs.h</em> and <em>lynx.cfg</em>, qv.</p>
<p>This is a Lynxism and should be used only in local documents
intended solely for <strong>Lynx</strong>, or for limited local
testing of CGI scripts without an http server.</p>
<hr>
<h2><a name="ncftp_url" id="ncftp_url">The <em>NcFTP</em>
URL:</a></h2>
<p><strong>Lynx</strong> recognizes the NcFTP-style ftp URL,
e.g.,</p>
<pre>
<cite>ftpHost</cite>:<cite>fileSpecification</cite>
</pre>
<p>for example</p>
<pre>
<code>
ftp.gnu.org:/pub/gnu
</code>
</pre>
<hr>
<h2><a name="internal_url" id="internal_url">The <em>LYNXfoo</em>
internal URLs:</a></h2>
<p><strong>Lynx</strong> uses a variety of private URL schemes
for communication among its internal modules. They start with
uppercase letters <code>LYNX</code> by convention, although, as
input, URL schemes are recognized in a case-insensitive
manner.</p>
<p>As you discover what they are, and are tempted to use them
externally in documents, you should <em>resist</em> that
temptation:</p>
<ul>
<li>There already is too much browser-specific markup
around...</li>
<li>The schemes, or their meanings, may change between
<strong>Lynx</strong> versions.</li>
<li>Even if a scheme stays the same, some aspect of its
behavior may be modified without notice, or the context in
which it is allowed may change.</li>
<li>If it does not work as expected when used outside of the
intended purpose, do not expect anyone to "fix" it.</li>
</ul>
<p>For example, tempting though it might be, do not use
these:</p>
<pre>
<em>Return to your <A HREF="LYNXHIST:0">Startfile</A></em>
<em>Review your <A HREF="LYNXKEYMAP:">Keymap</A></em>
</pre>
<p>(No, they will not do any harm. Yes, they work. But do not
rely on it.)</p>
<p>If you must try one, the second is OK from the command
line:<br></p>
<pre>
<em>lynx LYNXKEYMAP:</em>
</pre>
<p>But within <strong>Lynx</strong>, use the
“<em>K</em>” keystroke command. Sometimes it may be
convenient to use a private scheme with
“<em>g</em>”oto, as in:</p>
<pre>
<em>g LYNXMESSAGES:</em>
<em>g LYNXCOMPILEOPTS:</em>
<em>g LYNXCFG:</em>
</pre>
<p>But again, there usually is a way in which those special pages
are meant to be reached that is more convenient.</p>
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