| Previous | Table of Contents | Next |
NOTE: Most search engines also allow you to use quotation marks (“”) to search for phrases. Check your search engine’s help for specific details.
You’ll probably find that even a search engine lists too many sites to look through. You can reduce the number of sites you find by narrowing your search. Correctly using some simple terms—AND, OR, and NOT—can help narrow thousands of sites down to just a few.
These aren’t your everyday AND, OR, and NOT. They come from the symbolic logic system developed by a 19th-century mathematician named George Boole. Boolean searches use a basic syntax made up of operators and search terms. Because the terms don’t work quite the same as in English grammar, make sure that you get them straight. Table 31.2 shows examples of how to use AND, OR, and NOT.
| Expression | Description | ||
|---|---|---|---|
| AND or + | Returns pages that contain all your search terms. If all words aren’t on the page, the page isn’t displayed. Use AND or + when you have dissimilar terms and want to narrow the results to a few precise hits. For example, BMW AND roadster or BMW + roadster will display only pages that contain both BMW and roadster on the page. | ||
| OR | Returns pages that contain any of your search terms. Use OR to return pages with any of the terms listed in your search. For example, BMW OR roadster will display all pages that contain either BMW, roadster, or both. | ||
| NOT | Returns pages that don’t contain words specified in your search (not supported by all search engines). | ||
Don’t be afraid to experiment. Try several different searches with the same goal in mind so that you can get a better feel for the results that some of these expressions and your search words or phrases return. You’ll find that some experimentation with search terms will help you become more adept at narrowing your selections to a manageable size.
Now that I’ve gone over URLs and searching on the Web, let’s look at some of the other access methods listed earlier in Table 31.1 in more detail. Each section provides a description of the service, how to access it with and without a browser, and a sampling of what information the service returns.
FTP, or File Transfer Protocol, is the method that the Internet uses to exchange files between computers. No matter what you’re searching for—software, documentation, FAQ lists, programs, or just about anything else—you probably can get a copy through anonymous FTP.
Anonymous FTP is a service that lets you retrieve data from around the Internet without having an account on that machine. By using anonymous FTP, you can access any files that the systems administrators on the remote system have made publicly available.
• See “Using FTP for Remote File Transfer,” p. 580
FTP supports ASCII-mode transfers for text files, and binary-mode transfers for other types of files. Fortunately, most Web clients automatically determine the file type for you, so you don’t have to worry about it. You usually can determine the type of archive or compression program that was used on the file by looking at the file extension. Table 31.3 lists the most common file extensions you’ll encounter.
| Extension | Description | ||
|---|---|---|---|
| .Z | Compressed with the UNIX compress program | ||
| .z | Probably compressed with the GNU gzip program or the UNIX compress program | ||
| .gz | Compressed with the GNU gzip program | ||
| .tar | An archive of several files created by the UNIX tar program | ||
| .zip | An archive of several files created by pkzip | ||
Sometimes you’ll find files that have been created by more than one of these methods. For example, the file programs.tar.Z is an archive of several files created by the tar utility and then compressed with the compress utility.
To use a Web client such as Netscape (which has built-in FTP support) to perform anonymous FTP transfers, replace the protocol portion of the URL with “ftp.” For example, to start an anonymous FTP session to sunsite.unc.edu, use the following URL:
This URL causes your Web client to try to make an FTP connection to sunsite.unc.edu and log you in as an anonymous FTP session. After your FTP session is established, you can navigate through directories and transfer files by clicking the hyperlinks displayed.
NOTE: Most anonymous FTP servers request that you use your e-mail address as your password. If you have problems, check that your e-mail preferences are set correctly in your browser.
To specify a non-anonymous FTP session in Netscape, enter
ftp://username@ftp.startup.com
where username is your user name and ftp.startup.com is where you want to go. You’ll then be prompted to enter your password.
NOTE: When you select a text file to transfer from a remote server in an FTP session, most Web clients display the file on-screen. You need to save the file to disk via a menu selection. Some Web browsers allow you to specify loading a file to disk rather than to the screen.
ON THE WEB:
For a listing of FTP sites via the Web, see the following page:
Just like with the Web, one major problem with anonymous FTP is figuring out where the files that you’re interested in are located on the Internet. To help users locate files, the archie system was created. archie is basically a search engine for anonymous FTP sites.
| Previous | Table of Contents | Next |