Chapter 18. The R (Rules) Configuration Command
Rules are like little if-then clauses,[245] existing inside rule sets, that test a pattern against an address and change the address if the two match. The process of converting one form of an address into another is called rewriting. Most rewriting requires a sequence of many rules because an individual rule is relatively limited in what it can do. This need for many rules, combined with the sendmail program’s need for succinct expressions, can make sequences of rules dauntingly cryptic.
In this chapter, we dissect the components of individual rules. In the next chapter. we will show how groups of rules can be combined to perform necessary tasks.
[245] * Actually, they can be either if-then or while-do clauses, but we gloss over that complexity for the moment.
Get sendmail, 4th Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
