UNIX for Dummies Questions & Answers

 
read input
 
        for ((x=1;x<4;x++)){
        v=`echo $input | cut -c $x`
        if [ $v !-eq (0-9) ]
        then
        echo "error"
        else
        continue
        fi
        }

for (( i=1 ; i<4 ; i++))
 do  
  read a 
  echo $a | egrep -w "[0-9]{1,3}" || echo "wrong input"
 done

read input
if egrep -q '^[0-9]{1,3}$' <<< "$input"; then
    your command here
else
    echo error
fi

read input
egrep -q '^[0-9]{1,3}$' <<< "$input" || { echo "$(basename "$0"): Wrong input" >&2; exit 1; }
the
rest
of
your
script