为单个命令取消设置的环境变量
问题描述：
在bash中，您可以通过设置环境变量单个命令
In bash, you can set an environmental variable for a single command using
FOO=bar somecommand
如果你想的取消设置的单个命令变量？
答
从技术上讲，他们没有环境变量，直到有人导出取值他们。但你至少可以将其设置为空：
Technically, they're not environment variables until someone exports them. But you can at least set them to empty:
FOO= some command
如果从环境中删除它们就足够了，你可以使用 ENV ：
If removing them from the environment is enough, you can use env:
env -u FOO somecommand