I want to check whether Swap space exist on a centos box in my bash script.Thus in cash there are no swap space on the server , then i can create swap.

I tried this approach

```
if [[ -n $(swapon -s) ]]; then
    :
else
   mkswap /dev/vda2 &> /dev/null
   swapon /dev/vda2
fi

```

Obviously it won't work since even when there is no swap `swapon -s` will return a string
`Filename Type Size Used Priority`