Automatically incrementing run number in bash script

counter.sh

#!/bin/bash

# counter for current run number
if [ ! -e "${HOME}/.counter" ]
then
    echo "creating counter file"
    echo "1" > ~/.counter
fi
while read line
do
    runNo=$line
done < ~/.counter

# Now do stuff with $runNo
echo $runNo

# update counter
let "runNo += 1"
echo "$runNo" > ~/.counter