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You know already that you can press the Tab key half way during typing a command or filename, and most shells will attempt to complete what you have started. But zsh also has the following features:

rpm --erase # shows installed packages

rpm -q # shows suboptions of the 'q' option

fg % # shows the names of background processes that could be

promoted to foreground processes

cvs checkout # shows possible modules to check out

make -f Makefile # shows the targets in Makefile

cd # shows directories only

There are many, many more completions built into zsh, and you can even program your own. The manual page zshcompctl tells you all about this.

Chapter 5. Web Browsers and Instant Messaging

For the everyday communications that millions of people love to use—web browsing and instant messaging, including Internet Relay Chat—Linux provides free software tools that match or exceed most proprietary offerings.

The World Wide Web

Everybody who has even the slightest connection with computers and has not heard about, or used, the World Wide Web, most have spent some serious time under a rock. Like word processors or spreadsheets some centuries ago, the Web is what gets many people to use computers at all in the first place. We cover here some of the tools you can use to access the Web on Linux.

Linux was from the beginning intimately connected to the Internet in general and the Web in particular. For example, the Linux Documentation Project (LDP ) provides various Linux-related documents via the Web. The LDP home page, located at http://www.tldp.org, contains links to a number of other Linux-related pages around the world. The LDP home page is shown in Figure 5-1.

Linux web browsers usually can display information from several types of servers, not just HTTP servers sending clients HTML pages. For example, when accessing a document via HTTP, you are likely to see a page such as that displayed in Figure 5-1--with embedded pictures, links to other pages, and so on. When accessing a document via FTP, you might see a directory listing of the FTP server, as seen in Figure 5-2. Clicking a link in the FTP document either retrieves the selected file or displays the contents of another directory.

The way to refer to a document or other resource on the Web, of course, is through its Uniform Resource Locator, or URL. A URL is simply a pathname uniquely identifying a web document, including the machine it resides on, the filename of the document, and the protocol used to access it (FTP, HTTP, etc.). For example, the Font HOWTO, an online document that describes the optimal use of fonts on Linux, has the following URL:

Figure 5-1. LDP home page on the World Wide Web

http://www.tldp.org/HOWTO/html_single/Font-HOWTO/index.html

Let's break this down. The first part of the URL, http:, identifies the protocol used for the document, which in this case is HTTP. The second part of the URL, //www.tldp.org, identifies the machine where the document is provided. The final portion of the URL, HOWTO/html_single/Font-HOWTO/index.html, is the logical pathname to the document on www.tldp.org. This is similar to a Unix pathname, in that it identifies the file index.html in the directory HOWTO/html_single/Font-HOWTO. Therefore, to access the Font HOWTO, you'd fire up a browser, telling it to access http://www.tldp.org/HOWTO/html_single/Font-HOWTO/index.html. What could be easier?

Actually, the conventions of web servers do make it easier. If you specify a directory as the last element of the path, the server understands that you want the file index.html in that directory. So you can reach the Font HOWTO with a URL as short as:

Figure 5-2. FTP directory as displayed in the Konqueror web browser

http://www.tldp.org/HOWTO/html_single/Font-HOWTO/

To access a file via anonymous FTP, we can use a URL, such as:

ftp://ftp.ibiblio.org/pub/linux/docs/FAQ

This URL retrieves the Linux FAQ. Using this URL with your browser is identical to using ftp to fetch the file by hand.

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