Update README.md

README.md

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 # utility-format-usb.sh
 
-Partition and format any USB device using **exFAT** filesystem.
+## Description
+
+The scripts partitions and formats any USB device using **exFAT** filesystem. To avoid accidental format of non removable devices a couple of safeguards exist.
+
+The script will check if the supplied device is valid then it checks if the device is in fact a removable device. If any of these checks fail the script aborts.
+
+The script will ask for user confirmation twice and default to abort on <kbd>Enter</kbd>
+
+## Use case
+Re-purpose the USB stick if you have flashed an ISO to it.
+
+Why? Because writing an ISO using `dd` writes an ISO9660 filesystem to a small part of the USB - the rest is inaccessible.
+
+## Instructions
+Create the folder **~/.local/bin** and copy the file `format-usb.sh` into the folder, then make sure the file is executable.
+```
+mkdir -p ~/.local/bin
+chmod +x ~/.local/bin/format-usb.sh
+```
+
+## Usage
+Remove your USB if attached and list devices
+
+    lsblk
+
+Insert your USB device and list the devices
+
+    lsblk
+
+The new device in the list is your USB device e.g. /dev/sdy - format the device using the script
+
+    format-usb.sh /dev/sdy
+
+## Note
+What this script does can probably be done in numerous ways with numerous tools.
+
+The **list contains** validation is taken from this [stackoverflow topic][1]