[ -z "$VARIABLE" ] && VARIABLE="abc"
if env | grep -q ^VARIABLE=
then
echo env variable is already exported
else
echo env variable was not exported, but now it is
export VARIABLE
fi
我想强调的是,[ -z $VARIABLE ]
是不够的,因为你可以有VARIABLE
,但它没有出口.这意味着它根本不是一个环境变量.