Simple math in shell script

[Dallman Ross]

I really don't know how bc/dc work. I need to do some really simple math in a Bourne script. But there are decimal places, so I can't use

$(( expression ))

(which otherwise would work as a shell built-in).

E.g., what's the syntax for finding

$X / 100 + 1

?

I wish the man pages had damn example sections!

Thanks.

Dallman

[John McGaw]

I haven't used the Bourne shell for a long time and don't even have a system up at the moment which has it but I do recall that bc is the way to do floating point math within it. As for man pages not having examples, I guess it depends on who's man pages you are looking at. My old AT&T SVR4 man pages sure had examples. You might look at

which has some examples given.

BTW: this seems a _really_ silly group for this posting.

[Steve Thrasher]

Using bash....

x=`expr $x / 100 + 1` for x=200 will return a value of 3 since 200/100=2 and then add 1.

But if you were to: x=20000000;y=`expr 100 + 1`;x=`expr $x / $y` You get: 198019

Yeah...there's probably an easier way to do it.

[John McGaw]

Should have thought of this before: If $X is amenable, you can probably just perform the math as fixed-point by removing the decimal, calculating, and then re-insert the decimal in the proper location afterwards.

[Dallman Ross]

In , John McGaw spake thusly:

Ah. That's much better than the man page I have. Thanks!

You're right, and I apologize. I'm red-faced, but I thought I was in another group when I made that post. I'm surprised you guys didn't flame the hell out of me! Thanks. Your and Steve's answers were useful.

Regards, Dallman