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.20.If your local system does not support the -l option with Finger, you may be able to get the same effect by prefacingyour query with the two character sequence /w.This too is shown in Figure 3.20.Figure 3.20: Performing a Finger with Telnet.Neat Finger SitesFinger was intended to provide basic information about a system's users, but people soon learned they could do a lotmore with it than that.You can use Finger to access all kinds of information, from current weather conditions to publicencryption keys.Here are a few examples:Fingering this Gives youaurora@xi.uleth.ca Current northern lights informationforecast@typhoon.atmos.colostate.edu Tropical storm infodej@torfree.net Toronto Freenet informationScott Yanoff has produced two excellent online guides to Finger resources.Fingerinfo, shown in Figure 3.21, is aUNIX shell script that gives menu-driven access to some of the most interesting Finger sites.http://docs.rinet.ru/ITricks/tig03.htm (21 of 25) [4/18/1999 12:37:34 AM] Tricks of the Internet Gurus tig03.htmFigure 3.21.The Fingerinfo main menu.Yanoff's other guide, Special Internet Connections, shown in Figure 3.22, lists many different types of interestingInternet resources Finger, Telnet, e-mail, Gopher, and the World Wide Web.Figure 3.22.Special Internet Connections.This list is available both as a plain text file (Finger yanoff@alpha2.csd.uwm.edu for instructions on how to get thelatest version) and as a World Wide Web page:http://www.uwm.edu/Mirror/inet.services.htmlWorld Wide Web users may be interested to know that there is a gateway from World Wide Web to Finger.As shownin Figure 3.23, the gateway converts ordinary Finger output into hypertext by translating it into the Web's HypertextMarkup Language (HTML).Figure 3.23: The gateway from World Wide Web to Finger.Customizing Your Personal Finger InformationMost systems that support Finger also give users some control over what Finger says about them.Some UNIX systems support the chfn (change Finger information) command, which enables individual users to modifytheir own Finger information.The exact nature of the information you can modify with chfn varies from system tosystem.On DEC Ultrix systems, for example, you can change the text that Finger displays for your full name, youroffice address, and your office and home phone numbers.On most UNIX systems, if you create a file named.plan in your home directory, then the contents of that file will bedisplayed whenever someone fingers you, in addition to the usual Finger information.If you create a file named.project, the first line of that file will be displayed as well.On some systems, you can do even more exotic things and have Finger run a program every time you are fingered.Some people use this mechanism to provide up-to-the-minute information about themselves, while others use it to keeptrack of how often they are being fingered.On UNIX systems that allow it, this is done by turning your.plan file into a named pipe, setting up a program thatwrites to the pipe, and waiting for someone to finger you.Here's how to do it:First create a pipe named.plan in your home directory:% mknod.plan pThen run a program that writes to the pipe:% plan.sh &Here's a sample plan.sh script, which will send a different.plan file to each of the first five people who finger you:#!/bin/sh## sample script that runs a command via finger#count=0http://docs.rinet.ru/ITricks/tig03.htm (22 of 25) [4/18/1999 12:37:34 AM] Tricks of the Internet Gurus tig03.htmobject="person has"date=`/bin/date '+%r on %A %B %d, %Y'`while ( test $count -lt 5 )docount=`expr $count + 1`echo "$count $object fingered me since $date" >.planobject="people have"doneFinally, wait for some people to finger you, as shown in Figure 3.24.Figure 3.24: Running a program via Finger.GNU FingerAt most sites, the days of the large time-sharing central computer systems are gone, and this reduces the usefulness ofFinger.While at one time you could track someone down by fingering one or two large hosts, you may now have to tryhundreds or even thousands of smaller machines.And because people often have accounts on more than one system,even when you find them, you may not find the system they use most frequently.NetFind offers one solution to this problem.GNU Finger offers another.The GNU (Gnu's Not UNIX) version of Finger is a drop-in replacement for the standard UNIX Finger and fingerdprograms, which provides a site-wide (rather than system-wide) Finger service.At MIT, for example, you can finger gnu.ai.mit.edu to find people on any of fourteen machines in the MIT AI lab.GNU Finger offers several other extensions to the standard Finger protocol as well, including the ability to include"faces" (bit-mapped images) of users in the Finger output, and the ability to ask for general site information, such as alist of machines that are currently idle.Users can modify the information GNU Finger displays about them by creating an executable script named.fingerrc intheir home directory.If you have a.fingerrc file, GNU Finger filters the normal Finger output through this script beforepassing it on to the requestor, enabling you to modify, or completely replace, the usual information.Where to Get FingerAs mentioned earlier, if you do not have Finger client software, you can use Telnet to send a message directly to aremote Finger daemon instead.To finger user@host.domain, telnet to host.domain, port 79, and type the name of theuser you want to Finger, followed by a carriage return and linefeed.UNIX SystemsBoth the Finger client and server are included with most UNIX systems.GNU Finger is available from many sources,including anonymous FTP, fromlabrea.stanford.edu:/pub/gnu/finger-1.37.tar.gzhttp://docs.rinet.ru/ITricks/tig03.htm (23 of 25) [4/18/1999 12:37:34 AM] Tricks of the Internet Gurus tig03.htmMacintosh SystemsFinger client software for the Macintosh is available from many locations, includingarchive.umich.edu:/mac/util/network/finger1.37.sit.hqxA Finger client is included as part of Stanford's MacIP package and as part of the Mailstrom mail program.PC SystemsFinger client software is included with several commercial TCP/IP packages for the PC, including Sun's PC-NFS.A Windows Winsock Finger daemon is available fromsunsite.unc.edu:/pub/micro/pc-stuff/ms-windows/winsock/apps/fingerd.zipPingPing is one of the most basic Internet tools.It checks to see whether another machine on the network is reachable fromyour own host by sending it a message and waiting for a reply.The original BSD (Berkeley Standard Distribution) version of Ping is quite terse in its output, as can be seen in theexamples shown in Figure 3.25.Figure 3.25.A simple Ping.Later, and more sophisticated, versions of Ping keep trying until you ask them to stop, and they return moreinformation, such as the packet size, round-trip travel time, and the order in which the return packets arrive (icmp_seq),as shown in Figure 3.26.Figure 3.26.A fancier Ping.How Ping WorksPing uses the Internet Control Message Protocol (ICMP) to send messages across the network.Most of the Internet tools (Telnet, FTP, Finger, Gopher, World Wide Web, and so on) communicate across the networkusing the Internet's Transmission Control Protocol (TCP).TCP is a complex protocol that breaks messages up intopackets, sends them over the network, and puts them back together again at the other end.During transmission, packetsmay be lost, duplicated, or delayed, and TCP also includes mechanisms for detecting and dealing with these conditions
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