URL - Universal Resource Locator URI - Universal Resource Indicator (for all practical purposes, a URL is a URI - tomayto, tomahto) Absolute or "fully qualified" URL http://www.mcgill.ca/music/index.html "http://www.mcgill.ca/music/" is absolute. The trailing '/' indicates the default document in that directory. (usually "index.html") generically: SCHEME://SERVER_NAME:PORT_NUMBER/PATH_TO_FILE where: SCHEME normally identifies the protocol, such as http or ftp which is mapped to a port number SERVER_NAME is the actual hostname of a unique computer or "host" on the Internet.Notes on relative addressing
This is mapped to a numerical IP address by the Domain Name System
(e.g. "www.music.mcgill.ca" maps to "132.206.141.14") PORT_NUMBER is usually but not always implied by the SCHEME (e.g. http is port 80) PATH_TO_FILE is the full path to the file you seek from the DocumentRoot of the web server Relative URL FROM a base URL such as: http://www.mcgill.ca/ we can specify ./music/index.html to indicate: http://www.mcgill.ca/music/index.html eg: <img src="./graphics/image.gif"> There are many protocol schemes: http:// file:/// ftp:// news:// rtp:// rtsp://
To link to a file one folder level up from where we are use: ../ e.g.: <a href="../myfile.html"> To link to a file one folder level down from where we are use: ./FOLDER_NAME/myfile.html e.g.: <a href="./FOLDER_NAME/myfile.html"> To link to a file in the same folder as we are use: ./myfile.html e.g.: <a href="./myfile.html"> Where: . indicates the current directory .. indicates the directory above the current directory Note: It is good practice in relative addressing to always use "./" before a file path for files in the current directory.
World Wide Web Standards
Internet Standards
Open a Unix Shell: /Applications/Utilities/Terminal Note 1: use '<control>-c' to exit runaway processes Note 2: examples follow the '$' symbols Man: manual pages for any command man <command> $ man machine ... Ping: See if a network host is reachable $ ping bimbo.mcgill.ca ping: unknown host bimbo.mcgill.ca Traceroute: trace the internet routing and number of hops between two hosts $ traceroute www.ubc.ca traceroute to www.ubc.ca (137.82.194.43), 30 hops max, 40 byte packets 1 burnside1-msfc.gw.mcgill.ca (132.206.141.1) 1.761 ms 0.426 ms 0.323 ms 2 burnside-core-msfc.gw.mcgill.ca (132.216.216.41) 7.363 ms 0.403 ms 0.314 ms ... FTP: File Transfer Protocol : transfer files between network hosts $ ftp music.mcgill.ca Connected to music.mcgill.ca. 220 Welcome to the Faculty of Music, McGill University. Name (music.mcgill.ca:brouse): anonymous 331 Please specify the password. Password: //Just press return key 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp> ls 229 Entering Extended Passive Mode (|||51547|) 150 Here comes the directory listing. drwxr-xr-x 7 0 0 4096 Jul 05 16:10 pub 226 Directory send OK. ftp> quit 221 Goodbye. Host, Dig, and NSLookup: get information about a network host (IP address etc.) $ host www.mcgill.ca www.mcgill.ca is an alias for cochise.wcg.mcgill.ca. cochise.wcg.mcgill.ca has address 132.216.67.18 Whois: find out who an internet domain is registered to $ whois georgebush.com ..... netstat: find out about all active network connection for your host $ netstat ... ifconfig: configuration of network interfaces $ ifconfig ...