how to calculate percentage in shell

Question

I would like to calculate percentage in shell. But I can't do it. My script is

#!/bin/bash
#n1=$(wc -l < input.txt) #input.txt is a text file with 10000 lines
n1=10000
n2=$(awk '{printf "%.2f", $n1*0.05/100}')
echo 0.05% of $n1 is  $n2

It is neither showing any value nor terminating when executing this script.

Why can't you? Is an error stopping you? What's impeding you? — Andrew Li, Aug 24 '16 at 04:19
Possible duplicate of [How to use shell variables in awk script](http://stackoverflow.com/questions/19075671/how-to-use-shell-variables-in-awk-script) — tripleee, Aug 24 '16 at 05:11

score 3 · Accepted Answer · edited Aug 24 '16 at 04:36

3

awk will give you an n1 illegal field name if you do that, as it's inside single quotes. Also, to avoid awk keep reading stdin you should pass /dev/null as file. Then:

n2=$(awk -v n1="$n1" 'BEGIN {printf "%.2f", n1*0.05/100}' /dev/null)

edited Aug 24 '16 at 04:36

gsamaras

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answered Aug 24 '16 at 04:35

Diego Torres Milano

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score 1 · Answer 2 · answered Aug 24 '16 at 07:46

Rather than start a new process to count the records in the file and then passing that to awk, I would suggest you let awk count the records itself which it does anyway in the variable NR. So, your entire script would become:

percentage=$(awk 'END{print NR*0.05/100}' input.txt)

how to calculate percentage in shell

2 Answers2