If however you're trying to make a part for the kitset/toolbox, the following rules apply:
* error output goes to stderr, so it doesn't end up with the data * input/output can come from/to stdin/stdout, or file(s) * the only way to give parameters to the program (e.g. to control/modify its behaviour) is via command line arguments * in some cases, environment variables can be used instead of command line arguments (e.g. language settings which should affect all bits in the kitset) * on exit, success is 0, and anything !=0 is an error code.
These rules ensure that the program can easily be combined with the other bits already in the box.
A good summary Volker, to which I will add the following (rather obvious, which is why you probably omitted it) point:
* descriptive man page
Cheers, Carl.
