How to log into database via script securely?

How to log into database via script securely?

I am wondering about whether it is acceptable (security-wise) to have
database login credentials (user/pass) set in an environment variable or
passed in as a command-line parameter?
Both of these methods seem risky to me as perhaps others can read the
environment variable or read the running processes/history and credentials
would be there in plain-text (Is my understanding correct here?)
What would be an acceptable way to do this login? It would be run in a
script as part of an automated job/process.
Edit: This is an Oracle database (11g)