using negative exponents with bc in Bash

Question

I'm having a difficulty with using negative exponents in the program bc in Bash. If I execute echo "2*1.86929*10^05" | bc, I get a result of 373858.00000 while if I execute echo "2*1.86929*10^-05" | bc, I get a result only of 0. How can I get better accuracy when using negative exponents?

score 6 · Accepted Answer · answered Feb 28 '13 at 18:56

6

By default, the output of bc is rounded to an integer. To keep the decimal part of the result, use bc -l, like this:

$ echo "2*1.86929*10^-05" | bc -l
.00003738580000000000

answered Feb 28 '13 at 18:56

user000001

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This works well. Thank you very much for your assistance on this. – d3pd Mar 04 '13 at 15:09
1

`bc -l` should be the default for `bc`, in my opinion. – Lonnie Best Nov 02 '21 at 19:03

score 3 · Answer 2 · answered Feb 28 '13 at 18:58

3

You need to set the value of "scale" - so

scale=50
2*1.86929*10^-05

Gives .00003738580000000000000000000000000000000000000000

answered Feb 28 '13 at 18:58

DrC

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Thanks for your help on that. I got it working in the following way: ```echo "scale=50; 2*1.86929*10^-05" | bc```. – d3pd Oct 03 '14 at 11:31

using negative exponents with bc in Bash

2 Answers2