I connect to my Mac many USB devices that communicate over a serial (UART) bus to send debug information to the host or to receive data and code. You know, Raspberry Pi Picos, Adafruit Feathers, FTDI cables — that kind of thing. Often I have more than one connected. Is there an easy way to see what’s connected without listing /dev every time and to remember connected devices’ paths?

There is: I wrote a script. It’s in the form of a Z Shell function, so you can add it to your .zshrc file so it’s always ready to use.

Here it is:

dlist() {
    local devices=($(/bin/ls /dev/cu.usb* 2>/dev/null))
    if [ ${#devices} -gt 0 ]; then
        if [[ ${#devices} -eq 1 ]]; then
            echo $devices
        else
            local count=1
            for device in $devices; do
                if [[ -n "$1" && "$1" == "$count" ]]; then
                    echo $device
                elif [[ -z "$1" ]]; then
                    echo "$count. $device"
                fi
                ((count+=1))
            done
        fi
    fi
}

How does it work? Just run dlist at the command line to list connected serial devices. If there are more than one, they’re presented as a list:

1. /dev/cu.usbmodem1101
2. /dev/cu.usbserial-01AB8E0B

The beauty is that to use the device, just used $(dlist) anywhere you had previously entered the device’s file path. The shell calls the function and substitutes in the path.

For example, let’s say you want to send a file to a Pico running MicroPython. Then you’d use:

python -m pyboard.py -d $(dlist) -f cp main.py :main.py

No need to find out whether the device is at /dev/cu.usbserial-01AB8E0B or whatever, or to keep copying and pasting that path.

If you have multiple devices, just pass in the number of the device you want from the list. Let’s say device 2 is the one you want to send the file to, then you’d enter:

python -m pyboard.py -d $(dlist 2) -f cp main.py :main.py

Meanwhile you can be viewing debug logs from the other device with:

minicom -o -D $(dlist 1)

You can get the Z Shell function from this Gist.

For purists, there’s a separate version for Bash, implemented as an executable script, here.