Date: Wed, 7 Oct 92 14:28:18 -0500
In general there are two main class of shells. The first class are those shells derived from the Bourne shell which includes sh, ksh, bash, and zsh. The second class are those shells derived from C shell and include csh and tcsh. In addition there is rc which most people consider to be in a "class by itself" although some people might argue that rc belongs in the Bourne shell class.
With the classification above, using care, it is possible to write scripts that will work for all the shells from the Bourne shell category, and write other scripts that will work for all of the shells from the C shell category.