Checking whether /dev/video0 or /dev/ttyUSB0 exists or not (module is installed & probed). They're recognized as "character special file" in bash
[ -b /dev/ttyUSB0 ] && echo "char special file found" || echo "char special file not found" |
Compare the above to "block special file"
[ -b /dev/sda ] && echo "block special file found" || echo "block special file not found" |