Linux command internal command execution

A command may be both internal command is an external command
as an internal command a high priority, perform internal command

[04:21:44 root@C8[ ~]#type -a echo
echo is a shell builtin
echo is /usr/bin/echo

enable management of internal command

By enable can enable or disable the internal command
here is temporary disabled or enabled, quit or restart after failure

enable cmd 启用内部命令
enable –n cmd 禁用内部命令
enable –n 查看所有禁用的内部命令