Script to createuser

Hello All,

I am running Redhat 7.0.

I am trying to create a script that will add a user.  My script looks like
this:

echo 'createuser becky -d -a' | su postgres

When I run my script, I receive the following message even though the user
is created.

bash: /home/username/. bashrc:  Permission denied
CREATE USER

Why do I get this error and is there a way to get rid of it?

Thanks for the help!!
Rebecca