I think the command ``command'' is very useful, especially the -v option.
When the -v or -V option is used, the command utility shall provide information concerning how a command name is interpreted by the shell.
So you can do ``command -v program'' and get the location of ``program''. It's pretty neat.
Can sbase get this command, please?
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html