A good maxim of war is “know your enemy,” and the same advice applies to business. You need to know your customers or, on a web site, your visitors. Everything you can know about them is in the Environment variables (discussed in Chapter 16) that Apache gets from the incoming request. Apache’s logging directives, which are explained in this chapter, extract whichever elements of this data you want and write them to log files.
However, this is often not very useful data in itself. For instance, you may well want to track the repeated visits of individual customers as revealed by their cookie trail. This means writing rather tricky CGI scripts to read in great slabs of log file, break them into huge, multilevel arrays, and search the arrays to track the data you want.