- Avoid depending on the exact format of output from system (non-nmh)
programs.
+
+The Heirloom Bourne Shell, http://heirloom.sourceforge.net/sh.html,
+catches many non-portable shell constructs, such as $(), $(()), !, and
+assignment in export statements.
+
+checkbashisms, available at http://sourceforge.net/projects/checkbaskisms/,
+might help some catch problems. Though it misses all of the troublesome
+constructs, except for assignment in an export statement, listed above.
+
+The "Portable Shell" section of the Autoconf info manual has a wealth
+of tips for avoiding portability problems in shell scripts. It might
+be available by entering: info autoconf portable.