Merging upstream version 6.8.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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-.\" (C) Copyright 1999-2000 David A. Wheeler (dwheeler@dwheeler.com)
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.\" Fragments of this document are directly derived from IETF standards.
-.\" For those fragments which are directly derived from such standards,
-.\" the following notice applies, which is the standard copyright and
-.\" rights announcement of The Internet Society:
-.\"
-.\" Copyright (C) The Internet Society (1998).  All Rights Reserved.
-.\" This document and translations of it may be copied and furnished to
-.\" others, and derivative works that comment on or otherwise explain it
-.\" or assist in its implementation may be prepared, copied, published
-.\" and distributed, in whole or in part, without restriction of any
-.\" kind, provided that the above copyright notice and this paragraph are
-.\" included on all such copies and derivative works.  However, this
-.\" document itself may not be modified in any way, such as by removing
-.\" the copyright notice or references to the Internet Society or other
-.\" Internet organizations, except as needed for the purpose of
-.\" developing Internet standards in which case the procedures for
-.\" copyrights defined in the Internet Standards process must be
-.\" followed, or as required to translate it into languages other than English.
-.\"
-.\" Modified Fri Jul 25 23:00:00 1999 by David A. Wheeler (dwheeler@dwheeler.com)
-.\" Modified Fri Aug 21 23:00:00 1999 by David A. Wheeler (dwheeler@dwheeler.com)
-.\" Modified Tue Mar 14 2000 by David A. Wheeler (dwheeler@dwheeler.com)
-.\"
-.TH uri 7 2023-10-31 "Linux man-pages 6.7"
-.SH NAME
-uri, url, urn \- uniform resource identifier (URI), including a URL or URN
-.SH SYNOPSIS
-.SY "\fIURI\fP \fR=\fP"
-.RI [\~ absoluteURI
-|
-.IR relativeURI \~]
-.RB [\~\[dq] # \[dq]\~\c
-.IR fragment \~]
-.YS
-.P
-.SY "\fIabsoluteURI\fP \fR=\fP"
-.I scheme\~\c
-.RB \[dq] : \[dq]
-.RI (\~ hierarchical_part
-|
-.IR opaque_part \~)
-.YS
-.P
-.SY "\fIrelativeURI\fP \fR=\fP"
-.RI (\~ net_path
-|
-.I absolute_path
-|
-.IR relative_path \~)
-.RB [\~\[dq] ? \[dq]\~\c
-.IR query \~]
-.YS
-.P
-.SY "\fIscheme\fP \fR=\fP"
-.RB \[dq] http \[dq]
-|
-.RB \[dq] ftp \[dq]
-|
-.RB \[dq] gopher \[dq]
-|
-.RB \[dq] mailto \[dq]
-|
-.RB \[dq] news \[dq]
-|
-.RB \[dq] telnet \[dq]
-|
-.RB \[dq] file \[dq]
-|
-.RB \[dq] ftp \[dq]
-|
-.RB \[dq] man \[dq]
-|
-.RB \[dq] info \[dq]
-|
-.RB \[dq] whatis \[dq]
-|
-.RB \[dq] ldap \[dq]
-|
-.RB \[dq] wais \[dq]
-| \&...
-.YS
-.P
-.SY "\fIhierarchical_part\fP \fR=\fP"
-.RI (\~ net_path
-|
-.IR absolute_path \~)
-.RB [\~\[dq] ? \[dq]\~\c
-.IR query \~]
-.YS
-.P
-.SY "\fInet_path\fP \fR=\fP"
-.RB \[dq] // \[dq]\~\c
-.I authority
-.RI [\~ absolute_path \~]
-.YS
-.P
-.SY "\fIabsolute_path\fP \fR=\fP"
-.RB \[dq] / \[dq]\~\c
-.I path_segments
-.YS
-.P
-.SY "\fIrelative_path\fP \fR=\fP"
-.I relative_segment
-.RI [\~ absolute_path \~]
-.YS
-.SH DESCRIPTION
-A Uniform Resource Identifier (URI) is a short string of characters
-identifying an abstract or physical resource (for example, a web page).
-A Uniform Resource Locator (URL) is a URI
-that identifies a resource through its primary access
-mechanism (e.g., its network "location"), rather than
-by name or some other attribute of that resource.
-A Uniform Resource Name (URN) is a URI
-that must remain globally unique and persistent even when
-the resource ceases to exist or becomes unavailable.
-.P
-URIs are the standard way to name hypertext link destinations
-for tools such as web browsers.
-The string "http://www.kernel.org" is a URL (and thus it
-is also a URI).
-Many people use the term URL loosely as a synonym for URI
-(though technically URLs are a subset of URIs).
-.P
-URIs can be absolute or relative.
-An absolute identifier refers to a resource independent of
-context, while a relative
-identifier refers to a resource by describing the difference
-from the current context.
-Within a relative path reference, the complete path segments "." and
-".." have special meanings: "the current hierarchy level" and "the
-level above this hierarchy level", respectively, just like they do in
-UNIX-like systems.
-A path segment which contains a colon
-character can't be used as the first segment of a relative URI path
-(e.g., "this:that"), because it would be mistaken for a scheme name;
-precede such segments with ./ (e.g., "./this:that").
-Note that descendants of MS-DOS (e.g., Microsoft Windows) replace
-devicename colons with the vertical bar ("|") in URIs, so "C:" becomes "C|".
-.P
-A fragment identifier,
-if included,
-refers to a particular named portion (fragment) of a resource;
-text after a \[aq]#\[aq] identifies the fragment.
-A URI beginning with \[aq]#\[aq]
-refers to that fragment in the current resource.
-.SS Usage
-There are many different URI schemes, each with specific
-additional rules and meanings, but they are intentionally made to be
-as similar as possible.
-For example, many URL schemes
-permit the authority to be the following format, called here an
-.I ip_server
-(square brackets show what's optional):
-.P
-.IR "ip_server = " [ user " [ : " password " ] @ ] " host " [ : " port ]
-.P
-This format allows you to optionally insert a username,
-a user plus password, and/or a port number.
-The
-.I host
-is the name of the host computer, either its name as determined by DNS
-or an IP address (numbers separated by periods).
-Thus the URI
-<http://fred:fredpassword@example.com:8080/>
-logs into a web server on host example.com
-as fred (using fredpassword) using port 8080.
-Avoid including a password in a URI if possible because of the many
-security risks of having a password written down.
-If the URL supplies a username but no password, and the remote
-server requests a password, the program interpreting the URL
-should request one from the user.
-.P
-Here are some of the most common schemes in use on UNIX-like systems
-that are understood by many tools.
-Note that many tools using URIs also have internal schemes or specialized
-schemes; see those tools' documentation for information on those schemes.
-.P
-.B "http \- Web (HTTP) server"
-.P
-.RI http:// ip_server / path
-.br
-.RI http:// ip_server / path ? query
-.P
-This is a URL accessing a web (HTTP) server.
-The default port is 80.
-If the path refers to a directory, the web server will choose what
-to return; usually if there is a file named "index.html" or "index.htm"
-its content is returned, otherwise, a list of the files in the current
-directory (with appropriate links) is generated and returned.
-An example is <http://lwn.net>.
-.P
-A query can be given in the archaic "isindex" format, consisting of a
-word or phrase and not including an equal sign (=).
-A query can also be in the longer "GET" format, which has one or more
-query entries of the form
-.IR key = value
-separated by the ampersand character (&).
-Note that
-.I key
-can be repeated more than once, though it's up to the web server
-and its application programs to determine if there's any meaning to that.
-There is an unfortunate interaction with HTML/XML/SGML and
-the GET query format; when such URIs with more than one key
-are embedded in SGML/XML documents (including HTML), the ampersand
-(&) has to be rewritten as &amp;.
-Note that not all queries use this format; larger forms
-may be too long to store as a URI, so they use a different
-interaction mechanism (called POST) which does
-not include the data in the URI.
-See the Common Gateway Interface specification at
-.UR http://www.w3.org\:/CGI
-.UE
-for more information.
-.P
-.B "ftp \- File Transfer Protocol (FTP)"
-.P
-.RI ftp:// ip_server / path
-.P
-This is a URL accessing a file through the file transfer protocol (FTP).
-The default port (for control) is 21.
-If no username is included, the username "anonymous" is supplied, and
-in that case many clients provide as the password the requestor's
-Internet email address.
-An example is
-<ftp://ftp.is.co.za/rfc/rfc1808.txt>.
-.P
-.B "gopher \- Gopher server"
-.P
-.RI gopher:// ip_server / "gophertype selector"
-.br
-.RI gopher:// ip_server / "gophertype selector" %09 search
-.br
-.RI gopher:// ip_server / "gophertype selector" %09 search %09 gopher+_string
-.br
-.P
-The default gopher port is 70.
-.I gophertype
-is a single-character field to denote the
-Gopher type of the resource to
-which the URL refers.
-The entire path may also be empty, in
-which case the delimiting "/" is also optional and the gophertype
-defaults to "1".
-.P
-.I selector
-is the Gopher selector string.
-In the Gopher protocol,
-Gopher selector strings are a sequence of octets which may contain
-any octets except 09 hexadecimal (US-ASCII HT or tab), 0A hexadecimal
-(US-ASCII character LF), and 0D (US-ASCII character CR).
-.P
-.B "mailto \- Email address"
-.P
-.RI mailto: email-address
-.P
-This is an email address, usually of the form
-.IR name @ hostname .
-See
-.BR mailaddr (7)
-for more information on the correct format of an email address.
-Note that any % character must be rewritten as %25.
-An example is <mailto:dwheeler@dwheeler.com>.
-.P
-.B "news \- Newsgroup or News message"
-.P
-.RI news: newsgroup-name
-.br
-.RI news: message-id
-.P
-A
-.I newsgroup-name
-is a period-delimited hierarchical name, such as
-"comp.infosystems.www.misc".
-If <newsgroup-name> is "*" (as in <news:*>), it is used to refer
-to "all available news groups".
-An example is <news:comp.lang.ada>.
-.P
-A
-.I message-id
-corresponds to the Message-ID of
-.UR http://www.ietf.org\:/rfc\:/rfc1036.txt
-IETF RFC\ 1036,
-.UE
-without the enclosing "<"
-and ">"; it takes the form
-.IR unique @ full_domain_name .
-A message identifier may be distinguished from a news group name by the
-presence of the "@" character.
-.P
-.B "telnet \- Telnet login"
-.P
-.RI telnet:// ip_server /
-.P
-The Telnet URL scheme is used to designate interactive text services that
-may be accessed by the Telnet protocol.
-The final "/" character may be omitted.
-The default port is 23.
-An example is <telnet://melvyl.ucop.edu/>.
-.P
-.B "file \- Normal file"
-.P
-.RI file:// ip_server / path_segments
-.br
-.RI file: path_segments
-.P
-This represents a file or directory accessible locally.
-As a special case,
-.I ip_server
-can be the string "localhost" or the empty
-string; this is interpreted as "the machine from which the URL is
-being interpreted".
-If the path is to a directory, the viewer should display the
-directory's contents with links to each containee;
-not all viewers currently do this.
-KDE supports generated files through the URL <file:/cgi-bin>.
-If the given file isn't found, browser writers may want to try to expand
-the filename via filename globbing
-(see
-.BR glob (7)
-and
-.BR glob (3)).
-.P
-The second format (e.g., <file:/etc/passwd>)
-is a correct format for referring to
-a local file.
-However, older standards did not permit this format,
-and some programs don't recognize this as a URI.
-A more portable syntax is to use an empty string as the server name,
-for example,
-<file:///etc/passwd>; this form does the same thing
-and is easily recognized by pattern matchers and older programs as a URI.
-Note that if you really mean to say "start from the current location", don't
-specify the scheme at all; use a relative address like <../test.txt>,
-which has the side-effect of being scheme-independent.
-An example of this scheme is <file:///etc/passwd>.
-.P
-.B "man \- Man page documentation"
-.P
-.RI man: command-name
-.br
-.RI man: command-name ( section )
-.P
-This refers to local online manual (man) reference pages.
-The command name can optionally be followed by a
-parenthesis and section number; see
-.BR man (7)
-for more information on the meaning of the section numbers.
-This URI scheme is unique to UNIX-like systems (such as Linux)
-and is not currently registered by the IETF.
-An example is <man:ls(1)>.
-.P
-.B "info \- Info page documentation"
-.P
-.RI info: virtual-filename
-.br
-.RI info: virtual-filename # nodename
-.br
-.RI info:( virtual-filename )
-.br
-.RI info:( virtual-filename ) nodename
-.P
-This scheme refers to online info reference pages (generated from
-texinfo files),
-a documentation format used by programs such as the GNU tools.
-This URI scheme is unique to UNIX-like systems (such as Linux)
-and is not currently registered by the IETF.
-As of this writing, GNOME and KDE differ in their URI syntax
-and do not accept the other's syntax.
-The first two formats are the GNOME format; in nodenames all spaces
-are written as underscores.
-The second two formats are the KDE format;
-spaces in nodenames must be written as spaces, even though this
-is forbidden by the URI standards.
-It's hoped that in the future most tools will understand all of these
-formats and will always accept underscores for spaces in nodenames.
-In both GNOME and KDE, if the form without the nodename is used the
-nodename is assumed to be "Top".
-Examples of the GNOME format are <info:gcc> and <info:gcc#G++_and_GCC>.
-Examples of the KDE format are <info:(gcc)> and <info:(gcc)G++ and GCC>.
-.P
-.B "whatis \- Documentation search"
-.P
-.RI whatis: string
-.P
-This scheme searches the database of short (one-line) descriptions of
-commands and returns a list of descriptions containing that string.
-Only complete word matches are returned.
-See
-.BR whatis (1).
-This URI scheme is unique to UNIX-like systems (such as Linux)
-and is not currently registered by the IETF.
-.P
-.B "ghelp \- GNOME help documentation"
-.P
-.RI ghelp: name-of-application
-.P
-This loads GNOME help for the given application.
-Note that not much documentation currently exists in this format.
-.P
-.B "ldap \- Lightweight Directory Access Protocol"
-.P
-.RI ldap:// hostport
-.br
-.RI ldap:// hostport /
-.br
-.RI ldap:// hostport / dn
-.br
-.RI ldap:// hostport / dn ? attributes
-.br
-.RI ldap:// hostport / dn ? attributes ? scope
-.br
-.RI ldap:// hostport / dn ? attributes ? scope ? filter
-.br
-.RI ldap:// hostport / dn ? attributes ? scope ? filter ? extensions
-.P
-This scheme supports queries to the
-Lightweight Directory Access Protocol (LDAP), a protocol for querying
-a set of servers for hierarchically organized information
-(such as people and computing resources).
-See
-.UR http://www.ietf.org\:/rfc\:/rfc2255.txt
-RFC\ 2255
-.UE
-for more information on the LDAP URL scheme.
-The components of this URL are:
-.TP
-hostport
-the LDAP server to query, written as a hostname optionally followed by
-a colon and the port number.
-The default LDAP port is TCP port 389.
-If empty, the client determines which the LDAP server to use.
-.TP
-dn
-the LDAP Distinguished Name, which identifies
-the base object of the LDAP search (see
-.UR http://www.ietf.org\:/rfc\:/rfc2253.txt
-RFC\ 2253
-.UE
-section 3).
-.TP
-attributes
-a comma-separated list of attributes to be returned;
-see RFC\ 2251 section 4.1.5.
-If omitted, all attributes should be returned.
-.TP
-scope
-specifies the scope of the search, which can be one of
-"base" (for a base object search), "one" (for a one-level search),
-or "sub" (for a subtree search).
-If scope is omitted, "base" is assumed.
-.TP
-filter
-specifies the search filter (subset of entries
-to return).
-If omitted, all entries should be returned.
-See
-.UR http://www.ietf.org\:/rfc\:/rfc2254.txt
-RFC\ 2254
-.UE
-section 4.
-.TP
-extensions
-a comma-separated list of type=value
-pairs, where the =value portion may be omitted for options not
-requiring it.
-An extension prefixed with a \[aq]!\[aq] is critical
-(must be supported to be valid), otherwise it is noncritical (optional).
-.P
-LDAP queries are easiest to explain by example.
-Here's a query that asks ldap.itd.umich.edu for information about
-the University of Michigan in the U.S.:
-.P
-.nf
-ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US
-.fi
-.P
-To just get its postal address attribute, request:
-.P
-.nf
-ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US?postalAddress
-.fi
-.P
-To ask a host.com at port 6666 for information about the person
-with common name (cn) "Babs Jensen" at University of Michigan, request:
-.P
-.nf
-ldap://host.com:6666/o=University%20of%20Michigan,c=US??sub?(cn=Babs%20Jensen)
-.fi
-.P
-.B "wais \- Wide Area Information Servers"
-.P
-.RI wais:// hostport / database
-.br
-.RI wais:// hostport / database ? search
-.br
-.RI wais:// hostport / database / wtype / wpath
-.P
-This scheme designates a WAIS database, search, or document
-(see
-.UR http://www.ietf.org\:/rfc\:/rfc1625.txt
-IETF RFC\ 1625
-.UE
-for more information on WAIS).
-Hostport is the hostname, optionally followed by a colon and port number
-(the default port number is 210).
-.P
-The first form designates a WAIS database for searching.
-The second form designates a particular search of the WAIS database
-.IR database .
-The third form designates a particular document within a WAIS
-database to be retrieved.
-.I wtype
-is the WAIS designation of the type of the object and
-.I wpath
-is the WAIS document-id.
-.P
-.B "other schemes"
-.P
-There are many other URI schemes.
-Most tools that accept URIs support a set of internal URIs
-(e.g., Mozilla has the about: scheme for internal information,
-and the GNOME help browser has the toc: scheme for various starting
-locations).
-There are many schemes that have been defined but are not as widely
-used at the current time
-(e.g., prospero).
-The nntp: scheme is deprecated in favor of the news: scheme.
-URNs are to be supported by the urn: scheme, with a hierarchical name space
-(e.g., urn:ietf:... would identify IETF documents); at this time
-URNs are not widely implemented.
-Not all tools support all schemes.
-.SS Character encoding
-URIs use a limited number of characters so that they can be
-typed in and used in a variety of situations.
-.P
-The following characters are reserved, that is, they may appear in a
-URI but their use is limited to their reserved purpose
-(conflicting data must be escaped before forming the URI):
-.IP
-.in +4n
-.EX
-; / ? : @ & = + $ ,
-.EE
-.in
-.P
-Unreserved characters may be included in a URI.
-Unreserved characters
-include uppercase and lowercase Latin letters,
-decimal digits, and the following
-limited set of punctuation marks and symbols:
-.IP
-.in +4n
-.EX
-\- _ . ! \[ti] * ' ( )
-.EE
-.in
-.P
-All other characters must be escaped.
-An escaped octet is encoded as a character triplet, consisting of the
-percent character "%" followed by the two hexadecimal digits
-representing the octet code (you can use uppercase or lowercase letters
-for the hexadecimal digits).
-For example, a blank space must be escaped
-as "%20", a tab character as "%09", and the "&" as "%26".
-Because the percent "%" character always has the reserved purpose of
-being the escape indicator, it must be escaped as "%25".
-It is common practice to escape space characters as the plus symbol (+)
-in query text; this practice isn't uniformly defined
-in the relevant RFCs (which recommend %20 instead) but any tool accepting
-URIs with query text should be prepared for them.
-A URI is always shown in its "escaped" form.
-.P
-Unreserved characters can be escaped without changing the semantics
-of the URI, but this should not be done unless the URI is being used
-in a context that does not allow the unescaped character to appear.
-For example, "%7e" is sometimes used instead of "\[ti]" in an HTTP URL
-path, but the two are equivalent for an HTTP URL.
-.P
-For URIs which must handle characters outside the US ASCII character set,
-the HTML 4.01 specification (section B.2) and
-IETF RFC\~3986 (last paragraph of section 2.5)
-recommend the following approach:
-.IP (1) 5
-translate the character sequences into UTF-8 (IETF RFC\~3629)\[em]see
-.BR utf\-8 (7)\[em]and
-then
-.IP (2)
-use the URI escaping mechanism, that is,
-use the %HH encoding for unsafe octets.
-.SS Writing a URI
-When written, URIs should be placed inside double quotes
-(e.g., "http://www.kernel.org"),
-enclosed in angle brackets (e.g., <http://lwn.net>),
-or placed on a line by themselves.
-A warning for those who use double-quotes:
-.B never
-move extraneous punctuation (such as the period ending a sentence or the
-comma in a list)
-inside a URI, since this will change the value of the URI.
-Instead, use angle brackets instead, or
-switch to a quoting system that never includes extraneous characters
-inside quotation marks.
-This latter system, called the 'new' or 'logical' quoting system by
-"Hart's Rules" and the "Oxford Dictionary for Writers and Editors",
-is preferred practice in Great Britain and in various European languages.
-Older documents suggested inserting the prefix "URL:"
-just before the URI, but this form has never caught on.
-.P
-The URI syntax was designed to be unambiguous.
-However, as URIs have become commonplace, traditional media
-(television, radio, newspapers, billboards, etc.) have increasingly
-used abbreviated URI references consisting of
-only the authority and path portions of the identified resource
-(e.g., <www.w3.org/Addressing>).
-Such references are primarily
-intended for human interpretation rather than machine, with the
-assumption that context-based heuristics are sufficient to complete
-the URI (e.g., hostnames beginning with "www" are likely to have
-a URI prefix of "http://" and hostnames beginning with "ftp" likely
-to have a prefix of "ftp://").
-Many client implementations heuristically resolve these references.
-Such heuristics may
-change over time, particularly when new schemes are introduced.
-Since an abbreviated URI has the same syntax as a relative URL path,
-abbreviated URI references cannot be used where relative URIs are
-permitted, and can be used only when there is no defined base
-(such as in dialog boxes).
-Don't use abbreviated URIs as hypertext links inside a document;
-use the standard format as described here.
-.SH STANDARDS
-.UR http://www.ietf.org\:/rfc\:/rfc2396.txt
-(IETF RFC\ 2396)
-.UE ,
-.UR http://www.w3.org\:/TR\:/REC\-html40
-(HTML 4.0)
-.UE .
-.SH NOTES
-Any tool accepting URIs (e.g., a web browser) on a Linux system should
-be able to handle (directly or indirectly) all of the
-schemes described here, including the man: and info: schemes.
-Handling them by invoking some other program is
-fine and in fact encouraged.
-.P
-Technically the fragment isn't part of the URI.
-.P
-For information on how to embed URIs (including URLs) in a data format,
-see documentation on that format.
-HTML uses the format <A HREF="\fIuri\fP">
-.I text
-</A>.
-Texinfo files use the format @uref{\fIuri\fP}.
-Man and mdoc have the recently added UR macro, or just include the
-URI in the text (viewers should be able to detect :// as part of a URI).
-.P
-The GNOME and KDE desktop environments currently vary in the URIs
-they accept, in particular in their respective help browsers.
-To list man pages, GNOME uses <toc:man> while KDE uses <man:(index)>, and
-to list info pages, GNOME uses <toc:info> while KDE uses <info:(dir)>
-(the author of this man page prefers the KDE approach here, though a more
-regular format would be even better).
-In general, KDE uses <file:/cgi-bin/> as a prefix to a set of generated
-files.
-KDE prefers documentation in HTML, accessed via the
-<file:/cgi-bin/helpindex>.
-GNOME prefers the ghelp scheme to store and find documentation.
-Neither browser handles file: references to directories at the time
-of this writing, making it difficult to refer to an entire directory with
-a browsable URI.
-As noted above, these environments differ in how they handle the
-info: scheme, probably the most important variation.
-It is expected that GNOME and KDE
-will converge to common URI formats, and a future
-version of this man page will describe the converged result.
-Efforts to aid this convergence are encouraged.
-.SS Security
-A URI does not in itself pose a security threat.
-There is no general guarantee that a URL, which at one time
-located a given resource, will continue to do so.
-Nor is there any
-guarantee that a URL will not locate a different resource at some
-later point in time; such a guarantee can be
-obtained only from the person(s) controlling that namespace and the
-resource in question.
-.P
-It is sometimes possible to construct a URL such that an attempt to
-perform a seemingly harmless operation, such as the
-retrieval of an entity associated with the resource, will in fact
-cause a possibly damaging remote operation to occur.
-The unsafe URL
-is typically constructed by specifying a port number other than that
-reserved for the network protocol in question.
-The client unwittingly contacts a site that is in fact
-running a different protocol.
-The content of the URL contains instructions that, when
-interpreted according to this other protocol, cause an unexpected
-operation.
-An example has been the use of a gopher URL to cause an
-unintended or impersonating message to be sent via a SMTP server.
-.P
-Caution should be used when using any URL that specifies a port
-number other than the default for the protocol, especially when it is
-a number within the reserved space.
-.P
-Care should be taken when a URI contains escaped delimiters for a
-given protocol (for example, CR and LF characters for telnet
-protocols) that these are not unescaped before transmission.
-This might violate the protocol, but avoids the potential for such
-characters to be used to simulate an extra operation or parameter in
-that protocol, which might lead to an unexpected and possibly harmful
-remote operation to be performed.
-.P
-It is clearly unwise to use a URI that contains a password which is
-intended to be secret.
-In particular, the use of a password within
-the "userinfo" component of a URI is strongly recommended against except
-in those rare cases where the "password" parameter is intended to be public.
-.SH BUGS
-Documentation may be placed in a variety of locations, so there
-currently isn't a good URI scheme for general online documentation
-in arbitrary formats.
-References of the form
-<file:///usr/doc/ZZZ> don't work because different distributions and
-local installation requirements may place the files in different
-directories
-(it may be in /usr/doc, or /usr/local/doc, or /usr/share,
-or somewhere else).
-Also, the directory ZZZ usually changes when a version changes
-(though filename globbing could partially overcome this).
-Finally, using the file: scheme doesn't easily support people
-who dynamically load documentation from the Internet (instead of
-loading the files onto a local filesystem).
-A future URI scheme may be added (e.g., "userdoc:") to permit
-programs to include cross-references to more detailed documentation
-without having to know the exact location of that documentation.
-Alternatively, a future version of the filesystem specification may
-specify file locations sufficiently so that the file: scheme will
-be able to locate documentation.
-.P
-Many programs and file formats don't include a way to incorporate
-or implement links using URIs.
-.P
-Many programs can't handle all of these different URI formats; there
-should be a standard mechanism to load an arbitrary URI that automatically
-detects the users' environment (e.g., text or graphics,
-desktop environment, local user preferences, and currently executing
-tools) and invokes the right tool for any URI.
-.\" .SH AUTHOR
-.\" David A. Wheeler (dwheeler@dwheeler.com) wrote this man page.
-.SH SEE ALSO
-.BR lynx (1),
-.BR man2html (1),
-.BR mailaddr (7),
-.BR utf\-8 (7)
-.P
-.UR http://www.ietf.org\:/rfc\:/rfc2255.txt
-IETF RFC\ 2255
-.UE