below ism y code

if [ ip add show tun0 2>/dev/null ] ; then
    export http_proxy="http://127.0.0.1:2123"
fi

But when i do echo after conencting

echo $http_proxy

it is not displaying. can advice?

CodePudding user response：

@GordonDavisson suggested:

if ip add show tun0 2>/dev/null
then
   export http_proxy='http://127.0.0.1:2123'
fi

but you could also write it like this:

ip add show tun0 2>/dev/null && export http_proxy='http://127.0.0.1:2123'

ip will print stuff on stdout when successful, so maybe you want to do >& /dev/null? Instead of throwing all the data away, consider storing it in a variable, then you can always add a verbose flag to your program at some later point to print the content of that variable if you need to debug it.