Fibonacci series -going into infinite loop

Shell Programming and Scripting
1

Hello, I am a beginner to shell programming. Coded the following for Fibonacci series.

#!/bin/bash
fib()  {

i=0
j=1
arr[0]=0
arr[1]=1

echo "enter the limit:"
read n

while [ $i -lt $n ]
do
    fo= expr $j - 1
    f1=$j
    f2= expr $j + 1
    arr[$f2]= expr ${arr[$f1]} + ${arr[$f0]}
    echo ${arr[$f2]}
    
    i= expr $i + 1
    j= expr $j + 1
    
done
}

fib

The program is going into infinite loop. From debugging I understood that updated i,j values are not being carried to next iteration of while loop. Why is it so? Can someone please help.

2

Hi, you must use backquote when you execute commande from variable affectation:

i=`expr $i + 1`

or

i=$(expr $i + 1)

or under bash, you needn't use expr, just:

((i++))
3

Please use code tags as required by forum rules!

You need to use command substitution for all your expr assignments, e.g.

i=$(expr $i + 1)
4

Thank you disedorgue & RudiC. The changes worked. :wink: