$ portpicker -h
Pick a free unused port (CLI)

Usage: portpicker [OPTIONS]

Options:
  -n <N>         Pick N free unused ports [default: 1]
  -h, --help     Print help
  -V, --version  Print version

$ portpicker -V
portpicker 0.3.4

$ portpicker
18247

$ portpicker -n 5
21717
15668
15259
22006
19870