In the Beginning...Was the Command Line by Neal Stephenson Page A

raised by contractors and who had never used any drill other than a Hole Hawg. Such a person, presented with the best and most expensive hardware-store drill, would not even recognize it as such. He might instead misidentify it as a child’s toy, or some kind of motorized screwdriver. If a salesperson or a deluded homeowner referred to it as a drill, he would laugh and tell them that they were mistaken—they simply had their terminology wrong. His interlocutor would go away irritated, probably feeling rather defensive about his basement full of cheap, dangerous, flashy, colorful tools.
    Unix is the Hole Hawg of operating systems, * and Unix hackers—like Doug Barnes and the guy in the Dilbert cartoon and many of the other people who populate Silicon Valley—are like contractors’ sons who grew up using only Hole Hawgs. They might use Apple/Microsoft OSes to write letters, play video games, or balance their checkbooks, but they cannot really bring themselves to take these operating systems seriously.

THE ORAL TRADITION
    Unix is hard to learn. The process of learning it is one of multiple small epiphanies. Typically you are just on the verge of inventing some necessary tool or utility when you realize that someone else has already invented it, and built it in, and this explains some odd file or directory or command that you have noticed but never really understood before.
    For example, there is a command (a small program, part of the OS) called “whoami,” which enables you to ask the computer who it thinks you are. On a Unix machine, you are always logged in under some name—possibly even your own! What files you may work with, and what software you may use, depends on your identity. When I started out using Linux, I was on a nonnetworked machine in my basement, with only one user account, and so when I became aware of the whoami command it struck me as ludicrous. But once you are logged in as one person, you can temporarily switch over to a pseudonym in order to access different files. If your machine is on the Internet, you can log on to other computers, provided you have a user name and a password. At that point the distant machine becomes no different in practice from the one right in front of you. These changes in identity and location can easily become nested inside each other, many layers deep, even if you aren’t doing anything nefarious. Once you have forgotten who and where you are, the whoami command is indispensible. I use it all the time.
    The file systems of Unix machines all have the same general structure. On your flimsy operating systems, you can create directories (folders) and give them names like Frodo or My Stuff and put them pretty much anywhere you like. But under Unix the highest level—the root—of the filesystem is always designated with the single character “/” and it always contains the same set of top-level directories:
     
    /usr /etc /var /bin /proc /boot /home /root /sbin /dev /lib /tmp
     
    Each of these directories typically has its own distinct structure of subdirectories. Note the obsessive use of abbreviations and avoidance of capital letters; this is a system invented by people to whom repetitive stress disorder is what black lung is to miners. Long names get worn down to three- or four-letter nubbins, like stones smoothed by a river.
    This is not the place to try to explain why each of the above directories exists and what is contained in them. At first it all seems obscure; worse, it seems deliberatelyobscure. When I started using Linux, I was accustomed to being able to create directories wherever I wanted and to give them whatever names struck my fancy. Under Unix you are free to do that, of course (you are free to do anything), but as you gain experience with the system you come to understand that the directories listed above were created for the best of reasons and that your life will be much easier if you follow along. (Within /home, by the way, you have pretty much