#!/bin/bash

# Regex is matched with the =~ operator

log='this is some content'
var='some'
reg=".* is ${var}.*"
if [[ $log =~ $reg ]]; then
  echo 'matched'
fi

# Example to test if variable is a whole number
re='^[0-9]+$'
if ! [[ $yournumber =~ $re ]] ; then
  echo "error: Not a number"
  exit 1
fi