来自help compgen：
$ help compgen
compgen: compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command] [-X filterpat] [-P prefix] [-S suffix] [word]
Display possible completions depending on the options.
Intended to be used from within a shell function generating possible
completions. If the optional WORD argument is supplied, matches against
WORD are generated.
Exit Status:
Returns success unless an invalid option is supplied or an error occurs.
选项[-abcdefgjksuv]代表什么？
换句话说，我想知道如何使用所有选项。