uri, url, urn - uniform resource identifier (URI), including a URL or URN
URI = [ absoluteURI | relativeURI ] [ "#" fragment ]
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part )
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ]
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ] scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | &zerosp;...
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ] scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | &zerosp;... hierarchical_part = ( net_path | absolute_path ) [ "?" query ]
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ] scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | &zerosp;... hierarchical_part = ( net_path | absolute_path ) [ "?" query ] net_path = "//" authority [ absolute_path ]
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ] scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | &zerosp;... hierarchical_part = ( net_path | absolute_path ) [ "?" query ] net_path = "//" authority [ absolute_path ] absolute_path = "/" path_segments
URI = [ absoluteURI | relativeURI ] [ "#" fragment ] absoluteURI = scheme ":" ( hierarchical_part | opaque_part ) relativeURI = ( net_path | absolute_path | relative_path ) [ "?" query ] scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | &zerosp;... hierarchical_part = ( net_path | absolute_path ) [ "?" query ] net_path = "//" authority [ absolute_path ] absolute_path = "/" path_segments relative_path = relative_segment [ absolute_path ]
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. URIs are the standard way to name hypertext link destinations for tools such as web browsers. The string "http://www.kernelnotes.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). 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|". A fragment identifier, if included, refers to a particular named portion (fragment) of a resource; text after a '#' identifies the fragment. A URI beginning with '#' refers to that fragment in the current resource.
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 ip_server (square brackets show what's optional):
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP)
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036,
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation This refers to local online manual (man) reference pages. The command name can optionally be followed by a parenthesis and section number; see 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)>. info - Info page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation This refers to local online manual (man) reference pages. The command name can optionally be followed by a parenthesis and section number; see 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)>. info - Info page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation This refers to local online manual (man) reference pages. The command name can optionally be followed by a parenthesis and section number; see 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)>. info - Info page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation This refers to local online manual (man) reference pages. The command name can optionally be followed by a parenthesis and section number; see 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)>. info - Info page documentation
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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>. man - Man page documentation This refers to local online manual (man) reference pages. The command name can optionally be followed by a parenthesis and section number; see 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)>. info - Info page documentation 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>. whatis - Documentation search
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 ip_server (square brackets show what's optional): ip_server = [ user [ : password ] @ ] host [ : port ] This format allows you to optionally insert a user name, a user plus password, and/or a port number. The 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@xyz.com:8080/> logs into a web server on host xyz.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 user name but no password, and the remote server requests a password, the program interpreting the URL should request one from the user. 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. http - Web (HTTP) server 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>. 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 key = value separated by the ampersand character (&). Note that 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 &. 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 <http://www.w3.org/CGI> for more information. ftp - File Transfer Protocol (FTP) 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 user name "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>. gopher - Gopher server The default gopher port is 70. 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". 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). mailto - Email address This is an email address, usually of the form name @ hostname . See 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>. news - Newsgroup or News message A 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>. A message-id corresponds to the Message-ID of IETF RFC 1036, without the enclosing "<" and ">"; it takes the form unique @ full_domain_name . A message identifier may be distinguished from a news group name by the presence of the "@" character. telnet - Telnet login 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/>. file - Normal file This represents a file or directory accessible locally. As a special case, host 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 glob (7) and glob (3)). 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 exam