When I do this command I get an error when there is something wrong with the eth3. RESC="1234" RESD="1234" RESO="1234" RESC=$(ssh -q vmx@$1 cat /sys/class/net/$2/carrier) RESO=$(ssh -q vmx@$1 cat /sys/class/net/$2/operstate) RESD=$(ssh -q vmx@$1 cat /sys/class/net/$2/dormant) cat: /sys/class/net/eth3/carrier: Invalid argument cat: /sys/class/net/eth3/dormant: Invalid argument How can I use the invalid argument inside the RESC and RESD variable Thanks