These Unix Spotlights are about some Unix commands that you might not know exist and a few things you can do with them.

**TL;DR: bc is a calculator.**

One of my favorite commands is `bc -l`

because I'm terrible at arithmetic. The `l`

(lowercase L) flag allows you to "use the predefined math routines"; practically, this means you get non-integer division and some sweet functions you can use. I'd recommend always using `bc -l`

over `bc`

.

```
$ bc -l
# It has some copyright stuff here.
> 22 - (13 / 2)
15.50000000000000000000
> quit
```

(I've added `>`

's here for my input in `bc`

.)

Sweet. Note that to get out of `bc`

you type the word `quit`

and it'll take you back to the shell.

What else can you do with `bc`

? If you wanted the **FULL EXPERIENCE** you could do a whole lot of crazy wild calculations and some programming stuff but you're probably better off doing those in your *Language Of Choice*™ or checking out Wolfram Alpha. But here's a few quick things I use in `bc`

:

```
# Square roots
sqrt(2)
1.41421356237309504880
# Natural log
l(10)
2.30258509299404568401
# Exponential
e(10)
22026.46579480671651695790
# Sine, input in radians
s(3.141592/2)
.99999999999994660254
# Cosine, input in radians
c(3.141592/2)
.00000032679489661922
```

One annoying thing is that constants like $e$ and $\pi$ aren't defined, but it's still pretty okay if you need a basic approximation of something.