[Chapter 12] 12.3 Spare Details of the masterindex Program<

This section presents a few interesting details of the program that might otherwise escape attention. The purpose of this section is to extract some interesting program fragments and show how they solve a particular problem. Our first fragment is from the script, whose job it is to standardize the index entries before they are sorted. This program takes as its input a record consisting of two tab-separated fields: the index entry and its page number. A colon is used as part of the syntax for indicating the parts of an index entry. Because the program uses a colon as a special character, we must provide a way to pass a literal colon through the program. To do this, we allow the indexer to specify two consecutive colons in the input. However, we can't simply convert the sequence to a literal colon because the rest of the program modules called by read three colon-separated fields. The solution is to convert the colon to its octal value using the "\\72" represents the octal value of a colon. (You can find this value by scanning a table of hexadecimal and octal equivalents in the file .) In the last program module, we use to convert the octal value back to a colon. Here's the code from The first thing you notice is that we make this substitution for each of the three fields separately, instead of having