Issue with a Bash loop that uses an integer

Question

So I looked up the examples of a while loop and put the script together as so and still am having issues. If I was to guess I would say it with the arithmetic part of the bc function.

I want the loop to run until I hit a thousand and then count how many times it ran. I am not to the counting part of the script yet as I am still just trying to get it to run (yes I know awk would be easier).

This is what I have so far:

#!/bin/bash
total=120 #this will be a variable that is read in from a menu but 120 is ok for now
while [ $total -lt 1000000 ]
do
echo $total
total=$(bc<<<"scale=2;$total +  $total * .1") #I don't know if I have to use "let" before total but it did not make a difference.
done.

I am getting an error with the line that starts with "total" but the structure of the command seems to fit all the examples I could find. What gives?

There are two lines that start with "total", but I would expect you to get an error on line 3, that starts with While, and I would expect the error to be While: command not found (the keyword "while" is not capitalized). Once that's fixed, I would expect errors about "1,000,000" not being an integer. — William Pursell
– William Pursell, Commented Apr 26, 2017 at 23:04
If I run this at the prompt it works fine but in a loop...not so much total=120 total=$(bc<<<"scale=2;$total + $total * .1");echo $total --and then the output is 132.0 — Grunt
– Grunt, Commented Apr 26, 2017 at 23:04

Harvey · Accepted Answer · 2017-04-27 00:04:16Z

3

Use bc for the comparison, too.

#!/usr/bin/env bash

total=120
while [ "$(bc <<< "$total < 1000000")" == 1 ]
do
    echo $total
    total=$(bc <<< "scale=2;$total +  $total * .1")
done

answered Apr 27, 2017 at 0:04

Harvey

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1 Comment

Grunt Over a year ago

THANKS SOO MUCH! I look forward to be the guy helping out in a few years.

codeforester · Accepted Answer · 2017-04-27 05:13:40Z

0

As long as you are dealing with integers, you can write your loop with the arithmetic expression (( ... )), without the need for an external command like bc:

#!/bin/bash
total=120
while ((total < 1000000)); do
  echo $total
  ((total = total + total / 10))
done

edited Apr 27, 2017 at 5:13

answered Apr 27, 2017 at 2:36

codeforester

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