"networksetup -- configuration tool for network settings in System Preferences." - man networksetup

networksetup is a standard tool on osx

Examples

shows the relevant info for the device named Wi-Fi

networksetup -getinfo "Wi-Fi"

shows all connected hardware ports

networksetup -listallhardwareports

Show all search domains

networksetup -listallnetworkservices |
  tail -n +2 |
  xargs -I :: networksetup -getsearchdomains "::"

Create a bunch of VLAN interfaces

for X in {1..32} ; do
  sudo networksetup -createVLAN "vlan${X}" en3 "${X}" ;
done ;

Delete a bunch of VLAN interfaces

for X in {1..32} ; do
  sudo networksetup -deleteVLAN "vlan${X}" en3 "${X}" ;
done ;