Allowing for USB-serial disconnects and reconnects

The sat modem has the ID_VENDOR_FROM_DATABASE Future Technology Devices International, Ltd

The GPS Dongle has  ID_VENDOR_FROM_DATABASE Prolific Technology inc

so we loop through the attached usb-serial devices with for DEV in /dev/ttyUSB*;

for each of them we ask info about them do udevadm info -q env -n $DEV /dev/ttyUSB | grep -w 'DEVNAME\|ID_VENDOR_FROM_DATABASE' ; done

for DEV in /dev/ttyUSB*; do udevadm info -q env -n $DEV /dev/ttyUSB | grep -w 'DEVNAME\|ID_VENDOR_FROM_DATABASE' ; done

Giving an output of  : 

DEVNAME=/dev/ttyUSB0
ID_VENDOR_FROM_DATABASE=Future Technology Devices International, Ltd
DEVNAME=/dev/ttyUSB1

ID_VENDOR_FROM_DATABASE=Prolific Technology, Inc.

Now we know which /dev/ttyUSB? is connected to which manufacturers device.