Arithmetic calculation on real numbers in Bourne Shell Script

Shell Programming and Scripting
1

I am begining to learn bourne shell and as a practice I have written a script which when given the purchase price and percentage of discount calculates the savings.

I somehow cannot figure out why my script fails to do arthimatic calculation on real numbers.

Could anyone look at the script and recommend where is the flaw.

Thanks in advance

#!/bin/sh
echo "Enter the Price of the item \$ \c"
read price
echo "What Percentage of discount is available \c"
read per
echo "Your Total Savings are \c"
sav=`expr \( $per / 100 | bc -l \) \* $price`
echo $sav
2

Either use "expr" or "bc" but not both.
Always do multiply before divide.

sav=`echo "(($price * $per) / 100)" | bc -l`
3

Sorry, but that didn't work

4

What does your current script look like?
What happened when you ran it?
What answers did you give to the questions?

Complete modified script. Only calculation line has changed. I have just tried it in Bourne Shell, Korn Shell and Posix Shell.

#!/bin/sh
echo "Enter the Price of the item \$ \c"
read price
echo "What Percentage of discount is available \c"
read per
echo "Your Total Savings are \c"
sav=`echo "(($price * $per) / 100)" | bc -l`
echo $sav
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5

It works when I copied the entire script, may be I had left someting.
Great Thanks

And the following method works too

6 
echo "scale=4; $per * $price / 100" | bc -l

or

sav=`echo "scale=4; $per * $price / 100" | bc -l`

Sometimes this format is easier to read.
The scale sets for # of decimal places,
then the math equation,
piped to the math calculator.

1 Like