Re: What is the ~ symbol for in the upper left of your keyboard?

Posted by MarkB on April 12, 2002 at 19:12:40 from (64.79.81.243):

In Reply to: What is the ~ symbol for in the upper left of your keyboard? posted by Un-computerman on April 11, 2002 at 18:20:31:

As Cheryl said, it's a tilde, and means "approximately". But why is it on your computer keyboard? After all there are many more common mathematical symbols that are NOT on your keyboard ( ÷ is a good example).

It turns out that the tilde is used in the UNIX operating system, and the designers of the original IBM-PC made sure that it could eventually support some flavor of UNIX. (How tilde ever got into UNIX I don't know.)

In UNIX shells, the tilde is used as shorthand for your home directory. For example, if your userid is "frank", then "~/foo" is the same as "/home/frank/foo". Likewise, when another user wants to reference frank's home directory, they can use "~frank" instead of "/home/frank". Unix commands can be quite long, so anything to shave off a few characters is useful.

Now, why do you sometimes see the tilde in URLs? Since the web was built on Unix, it is only natural that web server recognize the tilde convention. In the context of a URL, however, the tilde has a slightly different meaning than it does to a Unix shell. "~frank" in a URL refers to the location of frank's public web pages. By convention this is usually the directory "public_html" under the user's home directory. This is done for security, because you don't want a web user to be able to browse a user's home directory, let alone the web server's root directory. So the URL "http://www.webserver.com/~frank" will actually take you to the file "/home/frank/public_html/index.html", which is frank's home page.

Now let's get back to tractors!

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