How to make a statement that checks if something is divisible by something else without a remainder (BASH)

Question

#!/bin/bash


Echo “Enter a number”

Read  $number

If [$number ] ; then 

Echo “Your number is divisible by 5”

Else

Echo “Your number is not divisible by 5”

fi

the if [$number] statement is what I don't know how to set up

Answer 1

You can use a simpler syntax in Bash than some of the others shown here:

#!/bin/bash
read -p "Enter a number " number    # read can output the prompt for you.
if (( $number % 5 == 0 ))           # no need for brackets
then
    echo "Your number is divisible by 5"
else
    echo "Your number is not divisible by 5"
fi

Answer 2

No bc needed as long as it's integer math (you'll need bc for floating point though): In bash, the (( )) operator works like expr.

As others have pointed out the operation you want is modulo (%).

#!/bin/bash  

echo "Enter a number"
read number

if [ $(( $number % 5 )) -eq 0 ] ; then
   echo "Your number is divisible by 5"
else
   echo "Your number is not divisible by 5"
fi

Answer 3

How about using the bc command:

!/usr/bin/bash

echo “Enter a number”
read number
echo “Enter divisor”
read divisor
remainder=`echo "${number}%${divisor}" | bc`
echo "Remainder: $remainder"

if [ "$remainder" == "0" ] ; then
        echo “Your number is divisible by $divisor”
else
        echo “Your number is not divisible by $divisor”
fi

Answer 4

Nagul's answer is great, but just fyi, the operation you want is modulus (or modulo) and the operator is generally %.

Answer 5

I have done it in a different way. Check if it works for you.
Example 1 :

num=11;
[ `echo $num/3*3 | bc` -eq $num ] && echo "is divisible" || echo "not divisible"
Output : not divisible

Example 2 :

num=12;
[ `echo $num/3*3 | bc` -eq $num ] && echo "is divisible" || echo "not divisible"
Output : is divisible

Simple logic.

12 / 3 = 4
4 * 3 = 12 --> same number

11 / 3 = 3
3 * 3 = 9 --> not same number

Answer 6

Just in the interest of syntax neutrality and mending the overt infix notation bias around these parts, I've modified nagul's solution to use dc.

!/usr/bin/bash

echo “Enter a number”
read number
echo “Enter divisor”
read divisor
remainder=$(echo "${number} ${divisor}%p" | dc)
echo "Remainder: $remainder"

if [ "$remainder" == "0" ]
then
        echo “Your number is divisible by $divisor”
else
        echo “Your number is not divisible by $divisor”
fi

Answer 7

You could also use expr like so:

#!/bin/sh

echo -n "Enter a number: "
read number
if [ `expr $number % 5` -eq 0 ]
then
    echo "Your number is divisible by 5"
else
    echo "Your number is not divisible by 5"
fi