Classic Shell Scripting

Summary

A surprisingly large number of text processing jobs can be handled with the subset of awk that we have presented in this chapter. Once you understand awk's command line, and how it automatically handles input files, the programming job reduces to specifying record selections and their corresponding actions. This kind of minimalist data-driven programming can be extremely productive. By contrast, most conventional programming languages would burden you with dozens of lines of fairly routine code to loop over a list of input files, and for each file, open the file, read, select, and process records until end-of-file, and finally, close the file.

When you see how simple it is to process records and fields with awk, your view of data processing can change dramatically. You begin to divide large tasks into smaller, and more manageable, ones. For example, if you are faced with processing complex binary files, such as those used for databases, fonts, graphics, slide makers, spreadsheets, typesetters, and word processors, you might design, or find, a pair of utilities to convert between the binary format and a suitably marked-up simple text format, and then write small filters in awk or other scripting languages to manipulate the text representation.