Raspberry Pi OS • Re: How to read contents of flash drive when it's plugged in

Code:

ACTION=="add",    SUBSYSTEM=="usb", RUN="/opt/udev-connect.sh"ACTION=="remove", SUBSYSTEM=="usb", RUN="/opt/udev-disconnect.sh"

Code:

#!/bin/bash# udev-connect.shecho "Device connected. Starting service-port.service"systemctl start service-port.service

Code:

#!/bin/bash# udev-disconnect.shecho "Device disconnected. Stopping service-port.service"systemctl stop service-port.service

Code:

[Unit]Description=Service port flash drive handler[Service]Type=oneshotExecStart=/opt/connect-service-port-drive.shExecStopPost=/opt/disconnect-service-port-drive.shRemainAfterExit=yesRestart=no[Install]WantedBy=multi-user.target

Code:

#!/bin/bashecho "USB drive connected"echo "Mounting device..."# the /dev/sd# device will not be available right away, so we need to keep# trying to find it until it's actually found. It usually takes about 4 or 5# tries, but here we use a maximum of 100 triesMOUNTED=0TRIES=0while [ $TRIES -le 100 ] && [ $MOUNTED -ne 1 ]; do    echo "    ...attempt number $TRIES"    TRIES=$(($TRIES + 1))    # list block devices    #   * --output specifies which data to print    #   * --paths means show the full paths of the devices    #   * --json puts the output into JSON format    #   * | jq passes the output to the jq JSON parser    #   * -r causes jq to output a raw string (without quotes)    #   * '.blockdevices[] | select(.rm == true) | .children[0] | .name')    #         finds all the block devices that are removable and gets the first    #         child of each and selects the name attribute from the output.    # The final result should be either an empty string or the name of the    # device. However, I found that sometimes it was null    DEVICE_NAME=$(lsblk --output NAME,MOUNTPOINTS,RM --paths --json | jq -r '.blockdevices[] | select(.rm == true) | .children[0] | .name')    # if the device name is empty or null then just sleep a little and try    # again    if [ -z $DEVICE_NAME ] || [ $DEVICE_NAME == "null" ]; then        sleep 0.1s    else        # if we found the device, then we need to unmount any previously        # mounted devices. If there are multiple devices mounted at the        # location, the umount command will unmount one at a time. If there are        # no devices mounted, then the umount command will return a non-zero        # exit status. So here we just keep calling umount until we get an        # error (capped at 100 tries to prevent an infinite loop)        NEED_TO_UNMOUNT=1        UMOUNT_TRIES=0        while [ $NEED_TO_UNMOUNT == 1 ] && [ $UMOUNT_TRIES -le 100 ]; do            UMOUNT_TRIES=$(($UMOUNT_TRIES + 1))            umount /media/service_port            if [ $? != 0 ]; then                NEED_TO_UNMOUNT=0            fi        done        # mount the new device        mount $DEVICE_NAME /media/service_port        MOUNTED=1    fidoneif [ $MOUNTED == 1 ]; then    echo "Device mounted"else    echo "Failed to mount device"    exit 1fi# do actual work here and be able to read from /media/service_portecho "Done"