Q: How to check if Oracle is up, in a Pro*C program

I am writing a Pro*C program that executes from a web page that has many user enterable fields. However if the database is down (due to backups or some other reason) I don't want to make the people spend time entering all these fields then have "ORACLE ERROR, etc" pop up. How can I quickly check that the database is up before jumping to the web page??

I need the C code, not an idea.

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