Classic Shell Scripting

Summary

The original spellchecking prototype shows the elegance and power of the Unix Software Tools approach. With only one special-purpose program, an afternoon's worth of work created a usable and useful tool. As is often the case, experience with a prototype in shell was then applied to writing a production version in C.

The use of a private dictionary is a powerful feature of Unix spell. Although the addition of locales to the Unix milieu introduced some quirks, dictionaries are still a valuable thing to use, and indeed, for each chapter of this book, we created private dictionaries to make spellchecking our work more manageable.

The freely available ispell and aspell programs are large and powerful, but lack some of the more obvious features to make their batch modes useful. We showed how with simple shell script wrappers, we could work around these deficiencies and adapt the programs to suit our needs. This is one of the most typical uses of shell scripting: to take a program that does almost what you need and modify its results slightly to do the rest of your job. This also fits in well with the "let someone else do the hard part" Software Tools principle.

Finally, the awk spellchecker nicely demonstrates the elegance and power of that language. In one afternoon, one of us (NHFB) produced a program of fewer than 200 lines that can be (and is!) used for production spellchecking.