How to tell whetehr Python script called as CGI or from command line?

Mon Apr 16 08:05:37 EDT 2007

I'm writing a Python script that can either be called as a Cron job or
as a web page (i.e. as a CGI in response to an HTTP request). This is
to process the mailboxes on my web server (to which I don't have
command line access) to remove old messages. How do I find out whether
the script has been called as a Cron job or as a CGI? I need to know
this so I can format the output correctly, e.g. if this is a web
request I need to start the output with "Content-type: text/html\n
\n<html>", to do newlines by "<p>" or "<br>" etc.

Can I just access some header line which will always have a value in a
web request, but which will be None if running from the command line
or as a Cron job, or something similar? How?

Thanks - Rowan