btrfs_umount.sh

#!/bin/bash

# This script is just meant to clean up the mountpoints of the Btrfs
# (pseudo-RAID / JBOD) partition (data: single, metadata: raid1) on my
# SD cards. For some reason it gets automatically remounted sometimes,
# appending higher and higher numbers to the name of the mountpoint. So
# this script will unmount all the ones except the first one.

regex="^\/run\/media\/${USER}\/SD_BTRFS([0-9]+)$"

mapfile -t lines < <(mount -t btrfs)

for (( i = 0; i < ${#lines[@]}; i++ )); do
    line="${lines[${i}]}"

    mapfile -d' ' -t line_parts <<<"$line"
    line_parts[-1]="${line_parts[-1]%$'\n'}"

    dev="${line_parts[0]}"
    mnt_pt="${line_parts[2]}"

    if [[ ! -b $dev ]]; then
        continue
    fi

    if [[ $mnt_pt =~ $regex ]]; then
        printf '\n%s\n' "${mnt_pt}: unmounting..."
        sudo umount "$mnt_pt"
    fi
done

printf '\n'