在 Linux 中，如何从命令行（或 shell 脚本）仅检索活动网络接口的名称？如果有多个活动接口，我只想要一个（任意选择）。
我正在使用 Debian Stretch 并想安装flashplugin-nonfree. 我的apt/sources.list文件包含
deb http://ftp.ca.debian.org/debian/ stretch main contrib non-free
deb-src http://ftp.ca.debian.org/debian/ stretch main contrib non-free
deb http://security.debian.org/debian-security stretch/updates main contrib non-free
deb-src http://security.debian.org/debian-security stretch/updates main contrib non-free
# stretch-updates, previously known as 'volatile'
deb http://ftp.ca.debian.org/debian/ stretch-updates main contrib non-free
deb-src http://ftp.ca.debian.org/debian/ stretch-updates main contrib non-free
deb http://download.virtualbox.org/virtualbox/debian stretch contrib
deb http://www.deb-multimedia.org stretch main non-free
deb [arch=i386,amd64] http://mariadb.mirror.globo.tech/repo/10.2/debian stretch main
但是当我运行时sudo apt-get install flashplugin-nonfree，我收到此错误消息：
sudo apt-get install flashplugin-nonfree
Reading package lists... Done
Building …