bash files in linux code example

Example 1: shell file in linux

#!/bin/sh
ls

Example 2: bash "=~" example

$ [[ 45 =~ [0-9]+ ]] && echo "45 contains digits"
45 contains digits

$ [[ "hello" =~ [0-9]+ ]] && echo "hello doesnt contains digits"
$ [[ "hello" =~ [a-z]+ ]] && echo "hello contains alphabets"
hello contains alphabets