Mathematical expression in print command in Linux

Question

I can't get my mistake in this command:

a=2
b=5
c=3
printf "%.2f\t" "'$a'+'$c'*'$b'" > ofile.txt

I am getting the value as 50.00. But I should get it 17.00.

How to do this when a, b, c are floating values? e.g. a=2.4, b=5.1 and c=3.2

Denis · Accepted Answer · 2015-06-12T21:52:41.133

7

Your 2nd argument to printf is interpreted as the string '2', which has an ascii value of 50. If you want to do arithmetic, use arithmetic evaluation in bash:

printf "%.2f\t" "$((a+b*c))" > ofile.txt

edited Jun 12 '15 at 21:52

answered Jun 12 '15 at 08:36

Denis

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using `$` inside `((...))` isn't necessary – Jahid Jun 12 '15 at 13:08
This is not working for floating values of a or b or c. Any suggestions plz? – Kay Jun 12 '15 at 13:20
2

Sorry arithmetic in bash is integer only. For floating point values you have to use an external program such as bc. Also see http://stackoverflow.com/a/12722107/4999056 – Denis Jun 12 '15 at 21:51
1

@Jahid Correct. Well spotted. Thanks. – Denis Jun 12 '15 at 21:53

score 1 · Answer 2 · edited Jun 12 '15 at 13:07

1

printf "%.2f\t" "$(($a+$b*$c))" > yourname.txt

edited Jun 12 '15 at 13:07

Jahid

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answered Jun 12 '15 at 08:40

Fiido93

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Mathematical expression in print command in Linux

2 Answers2