bash example
Example 1: 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
Example 2: linux shell script
#!/bin/bash
echo "Hello World"