uuidfstab - Convert fstab contents to a format that uses UUID instead of /dev paths.

#!/bin/bash

function error {
	echo "$1" >&2
	exit 1
}

function show_usage_and_exit {
	error "Usage: $0 <path_to_fstab_file> [<new_fstab_file>]"
}

function process {
	local FSTABFILE=$1 NEWFSTABFILE=$2 LINE DEVICE TEMPFILE ID OUTPUTFILE

	if [[ -n $NEWFSTABFILE ]]; then
		: >> "$NEWFSTABFILE" || error "Unable to create file or write to file: $NEWFSTABFILE"
		OUTPUTFILE=$NEWFSTABFILE
	else
		TEMPFILE=$(exec mktemp)
		[[ -z $TEMPFILE || ! -f $TEMPFILE ]] && error "Unable to create temporary file."
		[[ -w $TEMPFILE ]] || error "Temporary file can't be written into."
		OUTPUTFILE=$TEMPFILE
	fi

	shopt -s extglob

	while read LINE; do
		DEVICE=${LINE%%+([[:space:]])*}
		PRINTED=false
		if [[ $DEVICE == /dev/* ]]; then
			ID=$(exec blkid "$DEVICE" | grep -o "UUID=[^[:space:]]\+" | cut -f 2 -d '"')
			if [[ -n $ID ]]; then
				echo "# $DEVICE = $ID" >&3
				echo "${LINE/$DEVICE/UUID=$ID}" >&3
				PRINTED=true
			fi
		fi
		[[ $PRINTED = false ]] && echo "$LINE" >&3
	done < "$FSTABFILE" 3> "$OUTPUTFILE"

	if [[ -z $NEWFSTABFILE ]]; then
		cat "$TEMPFILE" > "$FSTABFILE" || error "Unable to save modifications to fstab file."
		rm "$TEMPFILE" || echo "Warning: failed to delete temporary file: $TEMPFILE" >&2
	fi

	echo "Operation successful."
}

for A; do
	[[ $A = -h || $A = --help ]] && show_usage_and_exit
done

if [[ $# -ne 1 && $# -ne 2 ]]; then
	echo "Invalid number of arguments." >&2
	show_usage_and_exit
fi

process "$@"

# /dev/sda5 = d964a7a4-2354-4e4a-9d31-5d1983dd3d24
UUID=d964a7a4-2354-4e4a-9d31-5d1983dd3d24		/		ext4		noatime,data=writeback,nobarrier,commit=100,nouser_xattr,noacl		0 1