1. brew 安装bash-completion
brew install bash-completion
安装成功后根据提示在 ~/.bash_profilez文件中添加如下内容：
[ -f /usr/local/etc/bash_completion ] && . /usr/local/etc/bash_completion
执行source ~/.bash_profile 使生效
2. 从github下载文件到本地
将https://github.com/docker/machine/tree/master/contrib/completion/bash目录下的三个文件（docker-machine-prompt.bash，docker-machine-wrapper.bash，docker-machine.bash）下载到 /usr/local/etc/bash_completion.d/ 目录下
3. 在~/.bash_profile文件中追加如下内容：
source '/usr/local/etc/bash_completion.d/docker-machine-prompt.bash'
source '/usr/local/etc/bash_completion.d/docker-machine-wrapper.bash'
source '/usr/local/etc/bash_completion.d/docker-machine.bash'
PS1='[\u@\h \W$(__docker_machine_ps1)]\$ '
执行source ~/.bash——profile 使生效
