Revised from: Bash scripts and udev rules to handle USB auto mounting / unmounting

Tested:
Uses USB insert/remove to control a headless Raspberry Pi 3 with Raspian Jessie Lite

Changes:

• Implement more functions
• Improve comments
• Modify if-fi exit handling
• Add optional flag for auto processing on insert/remove
• Optional function for USB insert - copy file (future: read config/start streaming process)
• Optional auto shutdown for USB removal (future: close process started by insert)

Goals:

• Improve bash coding and learn by implementing suggestions
• Improve my understanding of if-fi blocks and using inline commands (I'm not confident at all when it comes to streamlining code)

Current Code:
Uses udev rules to automount USB and create folder for device. Optionally can use an init constant to cause the automount/dismount process to auto start a process (in this case copy a config file) and shutdown pi on removal.

Work Flow:

uDev rules 
   usb-initloader.sh   
      Insert -> usb-automount.sh
      Remove -> usb-unloader.sh

udev rules

# /etc/udev/rules.d/85-usb-loader.rules
# ADD rule: 
#       if  USB inserted, 
#       and flash drive loaded as sd#
#           pass on dev name and device formatting type
#       run short script to fork another processing script
#       run script to initiate another script (first script must finish quickly)
#             to mkdir and mount, process file
#
# reload rules on PI by: 
#                        sudo udevadm control --reload-rules
#
ACTION=="add", KERNEL=="sd*[0-9]", SUBSYSTEMS=="usb", RUN+="/home/pi/scripts/usb-initloader.sh ADD %k $env{ID_FS_TYPE}"
ACTION=="remove", KERNEL=="sd*[0-9]", SUBSYSTEMS=="usb", RUN+="/home/pi/scripts/usb-initloader.sh %k"

usb-initloader.sh

#!/bin/bash
#
# /home/pi/scripts/usb-initloader.sh
#
# this script uses udev rules 
# is initiated when usb device is inserted or removed
#
# ** DEVICE INSERTED - new USB device inserted **
# ---------------------------------------------
# should be called from a udev rule like:that passes 
#   1. "ADD", 
#   2. kernel device  (%k)
#   3. filesystem type $env(ID_FS_TYPE)
#
# ACTION=="add", KERNEL=="sd*[0-9]", SUBSYSTEMS=="usb", RUN+="/home/pi/scripts/usb-initloader.sh ADD %k $env(ID_FS_TYPE)"
#
# Mounts usb device on /media/<dev>
# Logs changes to /var/log/syslog
# use tail /var/log/syslog to look at latest events in log
#
# ** DEVICE REMOVED - USB device removed **
# ---------------------------------------------
# on remove - we only need the kernel device (%k)
# should be called from a udev rule like:
#
# ACTION=="remove", KERNEL=="sd*[0-9]", SUBSYSTEMS=="usb", RUN+="/home/pi/scripts/usb-initloader.sh %k"
#
# CONFIGURATION
#
# Location of the three scripts (** MUST match your udev rules **)
SCRIPT_DIR=/home/pi/scripts
#
# Location of Log File
LOG_DIR=/home/pi/logs
LOG_FILE="${LOG_DIR}/usb-automount.log"
#
# Mount folder (sda1 will be added underneath this)
MOUNT_DIR=/media
#
# Optional parameter to:
#   - auto start a program on ADD
#   - auto end program and shutdown pi on REMOVE
#
AUTO_START_FINISH=1 # Set to 0 if false; 1 if true

#
# Call speciality script and leave this one (with trailing "&")
#
if [ "$1" == "ADD" ]; then
    DEVICE="$2"    # USB device name (kernel passed from udev rule)
    DEVTYPE="$3"   # USB device formatting type
    echo "==> Adding USB Device $DEVICE" >> "$LOG_FILE"
    ${SCRIPT_DIR}/usb-automount.sh "$LOG_FILE" "$MOUNT_DIR" "$DEVICE" "$DEVTYPE" "$AUTO_START_FINISH" >> "$LOG_FILE" 2>&1&
else
    DEVICE="$1"    # USB device name (kernel passed from udev rule)
    echo "==> Unmounting USB Device $DEVICE" >> "$LOG_FILE"
    ${SCRIPT_DIR}/usb-unloader.sh "$LOG_FILE" "$MOUNT_DIR" "$DEVICE" "$AUTO_START_FINISH" >> "$LOG_FILE" 2>&1&
fi

usb-automount.sh

#!/bin/bash
#
# Script: /home/pi/scripts/usb-automount.sh
# make sure to chmod 0755 on this script
#
# USAGE: usb-automount.sh DEVICE FILESYSTEM
#   LOG_FILE    is the error/activity log file for shell (eg /home/pi/logs/usbloader.log)
#   MOUNT_DIR   is the full mount folder for device (/media/sda1)
#   DEVICE      is the actual device node at /dev/DEVICE (returned by udev rules %k parameter) (eg sda1)
#   FILESYSTEM  is the FileSystem type returned by rules (returned by udev rules %E{ID_FS_TYPE} or $env{ID_FS_TYPE} (eg vfat)
#
# In case the process of mounting takes too long for udev
# we call this script from /home/pi/scripts/usb-initloader.sh
# then fork out to speciality scripts
#
# Adapted for Raspberry Pi - Raspbian O/S
# from previous code found at:
# http://superuser.com/questions/53978/automatically-mount-external-drives-to-media-label-on-boot-without-a-user-logge
# and mount manager example at
# http://solvedforhome.com/?p=2806&v=3a52f3c22ed6
#
# Edited with many suggestions from @janos (http://codereview.stackexchange.com/users/12390/janos)
#
# Acknowledgement to:
#   http://www.shellcheck.net/
#   dostounix utility

LOG_FILE="$1"
MOUNT_DIR="$2"
DEVICE="$3"  # USB device name (from kernel parameter passed from rule)
FILESYSTEM="$4"
AUTO_START="$5" # Do we want to auto-start a new process? 0 - No; 1 - Yes

# check for defined log file
if [ -z "$LOG_FILE" ]; then
    exit 1
fi

# Define all parameters needed to auto-start program
if [ "$AUTO_START" == "1" ]; then
    CONFIG_FILE="autostart-settings.cfg" # Check for this file on USB to initiate program with user-defined settings
    STARTUP_FOLDER="/home/pi/autostart"  # Start up folder to copy settings file into
fi

# Functions:
# #########
#
# automount function to test/make/mount USB device 
#
automount() {

    dt=$(date '+%Y-%m-%d/ %H:%M:%S')
    echo "--- USB Auto Mount --- $dt"

    #check input parameters
    if [ -z "$MOUNT_DIR" ]; then
        echo "Missing Parameter: MOUNT_DIR"
        exit 1
    fi
    if [ -z "$DEVICE" ]; then
        echo "Missing Parameter: DEVICE"
        exit 1
    fi
    if [ -z "$FILESYSTEM" ]; then
        echo "Missing Parameter: FILESYSTEM"
        exit 1
    fi

    # Allow time for device to be added
    sleep 2

    # test for this device is already mounted
    device_mounted=$(grep "$DEVICE" /etc/mtab)
    if [ "$device_mounted" ]; then
        echo "Error: seems /dev/$DEVICE is already mounted"
        exit 1
    fi

    # test mountpoint - it shouldn't exist
    if [ -e "$MOUNT_DIR/$DEVICE" ]; then
        echo "Error: seems mountpoint $MOUNT_DIR/$DEVICE already exists"
        exit 1
    fi

    # make the mountpoint
    sudo mkdir "$MOUNT_DIR/$DEVICE"

    # make sure the pi user owns this folder
    sudo chown -R pi:pi "$MOUNT_DIR/$DEVICE"

    # mount the device base on USB file system
    case "$FILESYSTEM" in

        # most common file system for USB sticks
        vfat)  sudo mount -t vfat -o utf8,uid=pi,gid=pi "/dev/$DEVICE" "$MOUNT_DIR/$DEVICE"
              ;;

        # use locale setting for ntfs
        ntfs)  sudo mount -t auto -o uid=pi,gid=pi,locale=en_US.UTF-8 "/dev/$DEVICE" "$MOUNT_DIR/$DEVICE"
              ;;

        # ext2/3/4 do not like uid option
        ext*)  sudo mount -t auto -o sync,noatime "/dev/$DEVICE" "$MOUNT_DIR/$DEVICE"
              ;;
    esac

    device_mounted=$(grep "$DEVICE" /etc/mtab)
    if [ "$device_mounted" == "" ]; then
        echo "Error: Failed to Mount $MOUNT_DIR/$DEVICE"
        exit 1
    fi

    echo "SUCCESS: /dev/$DEVICE successfully mounted as $MOUNT_DIR/$DEVICE"
}

# Auto Start Funmction
autostart() {

    echo "--- USB Auto Start Program ---"

    look_for_cfg="$MOUNT_DIR/$DEVICE/$CONFIG_FILE"
    if [ -e "$look_for_cfg" ]; then
        echo "Copying Startup File to $STARTUP_FOLDER"
        cp -u  -p "$look_for_cfg" "$STARTUP_FOLDER"
    fi
}

automount >> "$LOG_FILE" 2>&1

if [ "$AUTO_START" == "1" ]; then
    autostart >> "$LOG_FILE" 2>&1
fi

usb-unloader.sh

#!/bin/bash
# /home/pi/scripts/usb-unloader.sh
#
# Called from {SCRIPT_DIR}/usb-initloader.sh
#
# USAGE: usb-automount.sh DEVICE FILESYSTEM
#   LOG_FILE    is the error/activity log file for shell (eg /home/pi/logs/usbloader.log)
#   MOUNT_DIR   is the full mount folder for device (/media)
#   DEVICE      is the actual device node at /dev/DEVICE (returned by udev rules %k parameter) (eg sda1)
#
# UnMounts usb device on /media/<device>
# Logs changes to /var/log/syslog and local log folder
# use tail /var/log/syslog to look at latest events in log
#
# SUPPLIED PARAMETERS
#####################
LOG_FILE="$1"
MOUNT_DIR="$2"
DEVICE="$3"  # USB device name (from kernel parameter passed from rule)
AUTO_END="$4"  # Set to 0 if not wanting to shutdown pi, 1 otherwise
#
# check for defined log file
if [ -z "$LOG_FILE" ]; then
    exit 1
fi

#
# FUNCTIONS
###########
#
# autounload function to unmount USB device and remove mount folder
#
autounload() {

    dt=$(date '+%Y-%m-%d %H:%M:%S')
    echo "--- USB UnLoader --- $dt"

    if [ -z "$MOUNT_DIR" ]; then
        echo "Failed to supply Mount Dir parameter"
        exit 1
    fi
    if [ -z "$DEVICE" ]; then
        echo "Failed to supply DEVICE parameter"
        exit 1
    fi

    # Unmount device
    sudo umount "/dev/$DEVICE"

    # Wait for a second to make sure async  umount has finished
    sleep 1

    # Remove folder after unmount
    sudo rmdir "$MOUNT_DIR/$DEVICE"

    # test that this device has disappeared from mounted devices
    device_mounted=$(grep "$DEVICE" /etc/mtab)
    if [ "$device_mounted" ]; then
        echo "/dev/$DEVICE failed to Un-Mount"
        exit 1
    fi

    echo "/dev/$DEVICE successfully Un-Mounted"

}

autounload >> "$LOG_FILE" 2>&1

# kill auto-start process and shutdown
if [[ "$AUTO_END" == "1" ]]; then
    sudo shutdown -H 0
fi