Burn ISO file to USB under Mac OS command line

Use following command to find the connected USB device.

system_profiler SPUSBDataType | grep -iC 1 "BSD"

i :: ignore case
C 1 :: print 1 lines before and after the matching string
BSD :: Search string. In this example, BSD is the search string.

Unmount the USB drive using following command. If the USB has multiple partition, need to unmount all the listed disks from previous command.

diskutil unmountdisk /dev/disk2

Use following command to write ISO file on USB 

sudo dd if=ubuntu-18.04.3-live-server-amd64.iso of=/dev/disk2 bs=1M status=progress

dd:: Start dd command to write DVD/CD iso image.
if=/*iso:: Path to input file.
of=/dev/disk2:: Path to destination USB disk/stick.
bs=1M:: read and write up to BYTES at a time. In this example, 1M at a time.
status=progress:: Display progress.