查看 Bash 内置函数的信息

help <command>

这将显示指定内置的 Bash 帮助（手动）页面。

例如，help unset 将显示：

unset: unset [-f] [-v] [-n] [name ...]
   Unset values and attributes of shell variables and functions.

   For each NAME, remove the corresponding variable or function.

   Options:
     -f    treat each NAME as a shell function
     -v    treat each NAME as a shell variable
     -n    treat each NAME as a name reference and unset the variable itself
       rather than the variable it references

   Without options, unset first tries to unset a variable, and if that fails,
   tries to unset a function.

   Some variables cannot be unset; also see `readonly'.

   Exit Status:
   Returns success unless an invalid option is given or a NAME is read-only.

要查看包含简短描述的所有内置列表，请使用

help -d