burakkilic,

I normally use awk for this kind of problem - it works effectively

awk '{tot+=$1} END{print tot}' numbers.txt

Alternatively, change your script as shown:

#!/bin/sh
sum=0
for i in `cat numbers.txt |cut -f1`
do
sum=`expr $sum + $i` # Add back quotes around the expr
done
echo $sum


Steve