C Primer Plus®, Third Edition

A Simple-Minded File-Condensing Program

This next program copies selected data from one file to another. It opens two files simultaneously, using the "r" mode for one and the "w" mode for the other. The program (see Listing 12.2) condenses the contents of the first file by the brutal expedient of retaining only every third character. Finally, it places the condensed text into the second file. The name for the second file is the old name with .red (for reduced) appended. Command-line arguments, opening more than one file simultaneously, and filename appending are generally quite useful techniques. This particular form of condensing is of more limited appeal, but it can have its uses, as you will see.

Listing 12.2 The reducto.c program.

/* reducto.c ...