There are a couple of useful other ways to use bc that you didn’t mention.

The first is using “HERE files”. For example:

$ bc < < HERE
> 1+3
> last/2
> HERE
4
2
$

in this case, the > (and $ of course) are prompts from the interactive shell. However, the same thing works within a shell script. Shell variable expansion will apply to the content in the HERE file, so this can very powerful; the HERE file content doesn’t have to be static. Note that both numbers AND operators for bc can be represented in variables.

The second useful way to use bc is the backtick operator. AKA ‘results of’.

$ x=`echo 4+1|bc`
$ echo $x
5

This is kind of like ‘eval’ but it’s eval-ing a bc expression rather than a shell expression. Again, a pretty powerful construct.

Thanks for the ongoing stream of great geek stuff!
-Paul

Work the Shell – Solve: a Command-Line Calculator
http://www.linuxjournal.com/article/9891