Following up the previous case , here's something weran into recently.

Imagine that you want to pull lines out of /etc/shadow for specificlogin names; you'd use, for example, ' grep "^${UNAME}:" /etc/shadow '.Now imagine that some of your login names include '$', so you want togenerate a version of $UNAME with the '$' quoted.

So what do you have to write? It turns out that you

Here's something I would like to grind into various people programmingcallback email address verification:

Don't do callback email address verification with a MAIL FROM of <>unless the address has actually sent you email .

Why? Because if an address never sends any email to start with, it maynot be willing to receive bounces (the major source of email from <>).Blocking null MAIL FROMs from sending email to such addresses is acompletely rational way to block bad bounces from forged spam runs.

The