"Don’t allow arbitrary abbreviations of subcommands. [...] you allowed them to type any non-ambiguous prefix, like mycmd ins, or even just mycmd i, and have it

"Don’t allow arbitrary abbreviations of subcommands. [...] you allowed them to type any non-ambiguous prefix, like mycmd ins, or even just mycmd i, and have it be an alias for mycmd install. Now you’re stuck: you can’t add any more commands beginning with i, because there are scripts out there that assume i means install." Please avoid the use of short arguments in scripts. It makes the least sense there. The short arguments (along with aliases, abbreviations, and whatnot) are a convenience for human usage, to reduce the amount of manual typing. In scripts you can be explicit with minimal cost (and you also should, considering the ratio of writes vs. reads).