Problem with SU or SSH in shell script

Hi Floks!
This is Sravan!
I am new to linux and I am trying to write bash shell script in which I want to change the user but the statements which are after the "su " command are not working that I mean I want to execute some statements as the changed user

here is the code

      ls 
      su <<username>>
      ls

this code is executing but I am unable to execute the nxt cmd to su

please some one help me as I am running out of time

Thanks In Advance
Sravan Reddy
India

HI ,
Please add the following line to u r code as.There shld be -- followed by su
su -- <<username>>

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I will close this duplicate thread.