complete 命令
bash 的 complete 命令可以注册补全
$ complete --help
complete: complete [-abcdefgjksuv] [-pr] [-DE] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command] [-X filterpat] [-P prefix] [-S suffix] [name ...]
Specify how arguments are to be completed by Readline.
For each NAME, specify how arguments are to be completed. If no options
are supplied, existing completion specifications are printed in a way that
allows them to be reused as input.
Options:
-p print existing completion specifications in a reusable format
-r remove a completion specification for each NAME, or, if no
NAMEs are supplied, all completion specifications
-D apply the completions and actions as the default for commands
without any specific completion defined
-E apply the completions and actions to "empty" commands --
completion attempted on a blank line
When completion is attempted, the actions are applied in the order the
uppercase-letter options are listed above. The -D option takes
precedence over -E.
Exit Status:
Returns success unless an invalid option is supplied or an error occurs.
-W wordlist
使用 -W 可以注册固定的补全信息：
$ complete -W "red green blue yellow purple pink orange" color
$ color <TAB><TAB>
blue green orange pink purple red yellow
$ color p<TAB><TAB>
pink purple
$ color pi<TAB> # completes to pink
-F function
使用 -F 可以注册一个函数处理命令行补全，这个函数在运行时需要获取当前命令行的信息，bash 会将这些信息写入环境变量，通过这种方式，补全函数可以在运行时获取信息：
$COMP_LINE：当前命令行内容$COMP_WORDS：当前命令行内容按词分割的数组$COMP_POINT：光标的位置
函数执行之后，通过设置环境变量 $COMPREPLY 指定补全内容。
function _fizzbuzz () {
length=${#COMP_WORDS[@]}
number=$((length - 1))
if ! ((number % 15)); then COMPREPLY=(fizzbuzz)
elif ! ((number % 3)); then COMPREPLY=(fizz)
elif ! ((number % 5)); then COMPREPLY=(buzz)
else COMPREPLY=($number)
fi
}
complete -F _fizzbuzz fizzbuzz
查看补全列表
$ complete
补全列表里可以看到很多通用的 function，比如 _service, _longopt，可以利用这些 function 为一些命令增加补全，比如：
complete -F _longopt tar