How to add values in a variable in Unix shell scripting?

17

I have two variables called count1 and count7

count7=0
count7=$(($count7 + $count1))

This shows an error "expression is not complete; more token required".

How should I add the two variables?

This question is tagged with unix

~ Asked on 2011-08-30 15:40:13

The Best Answer is


24

What is count1 set to? If it is not set, it looks like the empty string - and that would lead to an invalid expression. Which shell are you using?

In Bash 3.x on MacOS X 10.7.1:

$ count7=0
$ count7=$(($count7 + $count1))
-sh: 0 + : syntax error: operand expected (error token is " ")
$ count1=2
$ count7=$(($count7 + $count1))
$ echo $count7
2
$

You could also use ${count1:-0} to add 0 if $count1 is unset.

~ Answered on 2011-08-30 15:45:33


7

var=$((count7 + count1))

Arithmetic in bash uses $((...)) syntax.

You do not need to $ symbol within the $(( ))

~ Answered on 2015-02-16 16:24:02


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