To switch to a Different User

$ su -l user3

To Use su with sudo command

$ sudo su - user3

To run specific command as a different user

$ su -c pwd user3

To use a different shell

$ su -s /usr/bin/csh 

To Execute a command as different user with su command

$ su -c <command> user3

To use a different user in the same environment

$ su -p user3

$ su -m user3

regards,

T.Dhanasekar