When writing your own checks, there are some shell script programming
techniques you should avoid in order to make your code portable. The
-Bourne shell and upward-compatible shells like Bash and the Korn shell
+Bourne shell and upward-compatible shells like the Korn shell and Bash
have evolved over the years, but to prevent trouble, do not take
advantage of features that were added after @sc{unix} version 7, circa
1977. You should not use shell functions, aliases, negated character