So far, you’ve read about only a handful of the hundreds of Unix programs that are built into Mac OS X and ready to run. Yes, ls and sudo are very useful tools, but they’re only the beginning. Here’s a rundown of some more cool (and very safe) programs that await your experimentation.
If you don’t return to the $ prompt after using one of these commands, type q or, in some cases, quit; then hit Enter.
Mac OS 9, Mac OS X, and Windows aren’t the only operating systems that come with a basic calculator accessory; Unix is well equipped in this regard, too.
When you type bc and hit Enter, you get a copyright notice and then...nothing. Just type the equation you want to solve, such as 2+2, or 95+97+456+2-65, or (2*3)+165- 95*(2.5*2.5), and then press Enter. On the next line, bc instantly displays the result of your calculation.
(In computer land, * designates multiplication and / represents division. Note, too, that bc solves equations correctly; it calculates multiplication and division before addition and subtraction, and inner parentheses before the outer ones. For more bc tricks and tips, type man bc at the prompt.)
The kill program in Terminal simply force quits a program, as though by remote control. (It even works when you telnet or SSH into your Mac from a remote location, ...