bash math...can't divide!!

vous · 07-06-2009, 08:07 AM

I try to make a division like so:

VAR1=$(( 28331 / 33009));
echo "Result is: $VAR1";

It should come out with "Result is 6.05"....but no, it comes with:

$ Result is 0

When I do it with smaller numbers like 100 / 3 it works perfectly. What is the problem?

GazL · 07-06-2009, 08:17 AM

Quote:

Originally Posted by vous

I try to make a division like so:

VAR1=$(( 28331 / 33009));
echo "Result is: $VAR1";

It should come out with "Result is 6.05"....but no, it comes with:

$ Result is 0

When I do it with smaller numbers like 100 / 3 it works perfectly. What is the problem?

The Result isn't 6.5 at all. You're dividing a number by a number greater than itself so it will be 0.something.

The reason you're getting 0 is that the answer is given as a truncated integer.

ghostdog74 · 07-06-2009, 08:22 AM

use awk

Code:

awk 'BEGIN{print 28331 / 33009}'

pixellany · 07-06-2009, 08:32 AM

Code:

mherring@Ath:~$ echo $((100/3))
33

Hmmmm----not quite perfect........

There is a utility for bash that does real decimal math, but I don't remember what it is.

This is easier:

Code:

python
>>> 100./3
33.33333333
>>> 2/3
0
>>>2./3
0.66666666
>>>2/3.
0.66666666

Note how easy it tis to tell it you want integer or decimal math.....

GazL · 07-06-2009, 08:33 AM

Interesting. I didn't know awk could do math. I'll have to remember that one myself.

ghostdog74 · 07-06-2009, 08:38 AM

Quote:

Originally Posted by GazL

Interesting. I didn't know awk could do math. I'll
have to remember that one myself.

please see my sig on link on learning Gawk.

GazL · 07-06-2009, 08:58 AM

Quote:

Originally Posted by ghostdog74

please see my sig on link on learning Gawk.

Thanks ghost. I'll check those out sometime. I've always tended towards sed rather than awk, so never really gave it much more than a cursory glance.

jf.argentino · 07-06-2009, 10:44 AM

Maybe easier than gawk, you can invoke "bc" to do floating point arithmetic

jlinkels · 07-06-2009, 08:46 PM

Code:

echo "4 k 100 3 / p" | dc

or, if you like

Code:

answer=$(echo "4 k 100 3 / p" | dc)

yields: 33.3333

You guessed it, "4 k" determines the number of decimal places.

jlinkels

vous · 07-07-2009, 03:22 AM

This worked actually, thanks!

echo "scale=5; (54321 / 12345)" | bc