Working with decimal in bash if statement

Question

I have the below code which I'm trying to work out if a variable is lower than 95% of an average. My issue is that $avg its coming back with values that are not whole numbers 200.5 for example and bash doesn't like it. I'm not sure how to format my if in regards to the lower than.

servers=4
percentage=0.95
formula=$(($totalspace / $servers))
avg=$(echo $formula*$percentage | bc)

if [ $server1 -lt $avg ]
then

Thanks

DigitalRoss · Accepted Answer · 2016-04-06 16:15:34Z

3

You had the right idea shipping your calculation off to bc(1). Just carry that idea a little further and do the whole calculation there.

Things to keep in mind...

bc will also return integer results by default, use scale = 4 or something
bc can do the floating comparison too, relational operators return 0 or 1
you might want to quote the calculation even though your * surrounded by digits is unlikely to be expanded, because the shell will try anyway.

answered Apr 6, 2016 at 16:15

DigitalRoss

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2 Comments

jaseUK Over a year ago

avg=$(echo "scale=4;$average*$percentage" | bc ) doesn't seem to help

DigitalRoss Over a year ago

Well, all by itself, of course not, because bash can't compare the floating point result. As I said, you need to do the comparison (and the earlier calculations) in bc also.

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