To export just leave the filename blank as in this example:
xe vm-export vm=VM-UUID filename= | gzip -c > /mnt/vm.xva.gz
To import use /dev/stdin as filename:
gunzip -c /mnt/vm.xva.gz | xe vm-import sr-uuid=SR-UUID filename=/dev/stdin
To export just leave the filename blank as in this example:
xe vm-export vm=VM-UUID filename= | gzip -c > /mnt/vm.xva.gz
To import use /dev/stdin as filename:
gunzip -c /mnt/vm.xva.gz | xe vm-import sr-uuid=SR-UUID filename=/dev/stdin