CHAPTER 27 World Wide Web

27.2 URLs

Uniform Resource Locators, URLs, reference where a resource can be found in the form:

service_scheme://machine_name[:port_number]/directory/sub-directory_list/file[?keyword]

where the items in brackets are optional. Some of the more common service_schemes are:

ftp - file transfer protocol, a ";type=<type_code>" may be used to indicate the file type (e.g. an "I" for image, or an "A" for text)
http - hypertext transfer protocol
gopher - gopher protocol
nntp - Usenet news for local NNTP access
telnet, rlogin, or tn3270

The service_scheme could, optionally, include a user name and password, if required for the service.

The machine_name may be followed by a decimal port_number, separated from the machine_name by a colon, if something other than the default port number, 80, is used by the service.

The remainder of the address is the path, with subdirectories separated by "/" and ending with the desired file name or program. The latter may optionally be followed by a "?" and a keyword that can be used as an argument to the program. The specs for URLs can be found on:

http://info.cern.ch/hypertext/WWW/Addressing/URL/Overview.html

Unix System Administration - 8 AUG 1996

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