Question

I have somewhat wierd requirement to be resolved in Unix script.

supose i have a file containing

a=4
b=3
c=a+b
d=c+a
e=a+b+5+d

I have to get output like

a=4
b=3
c=7
d=11
e=23

I have tried using AWK using the logic that whatever in RHS variable avaiable I will replace it with ${variable}
for example

e=a+b+5+d

will comeout as

e=${a}+${b}+5+${d}

But I am not sure how to get value of "a,b,d" in the currently running shell in AWk. Used “source” keyword after writing the a=4 thing to file. but it is not working.

Please suggest some other way because I don’t think my way is going to work.

Answer 1

If you have the formulas in a file expr.sh, then this will work:

sed -e 's:=:=$((:' -e 's:$:)):' expr.sh |bash -x

Explanation: e=$((a+b+5+d)) will evaluate the expression between $(( and )) (including expanding all variables) and assign the result to e