There are times that you need to execute a script as another user, usually to make sure you do not mess up the access rights of the files that will be produced after the execution of the script.
An easy way to do it is using the command
su (su allows to run commands with a substitute user and group ID).
An example would be to use it as
su - <USER> -c "<COMMAND>”
The – <USER> will start the shell as a login shell with an environment similar to a real login.
The -c “<COMMAND>” will pass the command after -c to the newly created shell, you should wrap it in quotes if you want to pass parameters to your command.