how to check if character in string BASH code example

Example: check string in bash

#Check equality two string variables

if [ $strval1 == $strval2 ]; then
  echo "Strings are equal"
else
  echo "Strings are not equal"
fi

#Check equality of a variable with a string value

if [ $strval1 == "Ubuntu" ]; then
  echo "Linux operating system"
else
  echo "Windows operating system"
fi