Shell判断某个软件是否安装

方法1

if [ -x "$(command -v ufw)" ]; then
  echo "ufw installed!"
else
  echo 'Error: git is not installed.' >&2
  exit 1
fi

方法2 (与OS的发行版本有关）

if [[ $(apt list ufw) =~ "installed" ]]; then
echo "ufw installed"
else
echo "Error: ufw install failed!"; exit
fi