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I want to do some simple calculations with variables in an script.sh, in the same directory there is a folder called New Folder2. So, I want to enter into the folder and save a text file.

The script is the following:

#!/bin/bash
foldername='New Folder'
number=1
number=$number+1
cd $foldername$number
echo '$number' > number.txt

But then I only get the file number.txt in the same directory ./ with 1+1 not the actual sum. What should I do?

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2 Answers 2

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For integers, use arithmetic expansion: $(( EXPR ))

num=$((num1 + num2))
num=$((num + 1))
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3
  • It only works for integers? And what can I do for other types of variables?
    – Joshua Salazar
    Nov 17, 2016 at 15:57
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    @JoshuaSalazar you can use your way with strings a='hello' b='world' c=$a$b echo $c > helloworld
    – Wissam Roujoulah
    Nov 17, 2016 at 16:00
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    To concatenate/"add" strings you can just do something like $string="$string$anotherstring". Also, an alternative to the arithmetic expansion would be to use let number=$number+1, though I think the $(( )) syntax is more easily readable..
    – IanC
    Nov 17, 2016 at 16:02
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Look at 4th and 5th line!

#!/bin/bash
foldername='New Folder'
number=1
number=$((number+1))
cd "$foldername$number"
echo '$number' > number.txt
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