bash check if string contains code example

Example 1: check if variable contains string bash

STRING='Hello world'
if [[ $STRING =~ "Hello" ]] ; then echo "It's here" ; fi

Example 2: checking if a substring exists in a string bash

string='Haystack';

if [[ $string =~ "Needle" ]]
then
   echo "It's there!"
fi

Example 3: bash if file contains string

if grep -q SomeString "$File"; then
  Some Actions # SomeString was found
fi

Example 4: bash substring test

#!/bin/bash

STR='GNU/Linux is an operating system'
SUB='Linux'

if [[ "$STR" =~ .*"$SUB".* ]]; then
  echo "It's there."
fi

Example 5: bash if substring

string='Hi substring' #To check if string has "Mylong" substring do
if [[ $string == *"substring"* ]]; then
  echo "String has substring"
fi