How to add values in a variable in Unix shell scripting

Question

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

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var    count7   count1     Arithmetic in bash uses          syntax   You do not need to   symbol within the

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echo   x      x 10     echo   y  enter code here      y 10     echo    x  y    Answer  20

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read num1 read num2 sum  expr  num1    num2  echo  sum

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You can do this as well  Can be faster for quick calculations   echo   2 2

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Here s a simple example to add two variables   var1 4 var2 3 let var3  var1  var2 echo  var3

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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

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I don t have a unix system under my hands  but try this   count7      count7      count1     Or maybe you have a shell that doesn t support this expression  I think bash does support it  but sh doesn t   EDIT  There is another syntax  try   count7  expr  count7    count1

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the above script may not run in ksh  you have to use the  let  opparand to assing the value and then echo it   val1 4  val2 3  let val3  val1  val2  echo  val3

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In ksh  bash  sh     count7 0                        count1 5         count7    count1      echo  count7   5

[unix] How to add values in a variable in Unix shell scripting?

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