#!/bin.bash
 
regex='^[0-9]+$'
 
foo='1234'
bar='hi bean'
 
echo "foo = $foo"
 
if [[ "$foo" =~ $regex ]]; then
    echo "$foo is an integer"
else
    echo "$foo is a string"
fi
 
echo "bar = $bar"
 
if [[ "$bar" =~ $regex ]]; then
    echo "$bar is an integer"
else
    echo "$bar is a string"
fi