I am getting this error message: line 12: 470 + : syntax error: operand expected (error token is "+ ")
I still get my answer of 470 at the end but this error message display in the output and I cannot understand why. Can any one please explain?
Here is my code:
while IFS= read -r var
do
total=$(($total+$var))
done<"$input"
echo "The total is = $total";
echo
My final output each time:
line 12: 470 + : syntax error: operand expected (error token is "+ ")
The total is = 470
When you use a $ with a dereference inside an arithmetic expression, that prevents special arithmetic parsing rules (that treat an empty string as a 0) from being able to apply. Just take out the $s on the inside to fix your problem:
while IFS= read -r var; do
total=$((total+var))
done <"$input"
...or, for clearer (but bash-only) syntax:
while IFS read -r var; do
(( total += var ))
done <"$input"
Based on other comments, I would change to this to ignore empty lines and whitespace. I don't have your $input file, so I am just entering data directly in the shell and ending my data entry with the EOF indicator (<CTRL>d for me)
$ total=0;while IFS= read -r var; do [[ -n "${var##*\ }" ]] && total=$(($total+$var)) ; done
1
2
3
^D
$ echo ${total}
6
$varis empty in that last iteration of the loop. The file probably ends with a blank line$varis empty before using it${var}is undefined) you could default${var}to 0:${var:-0}