automatic image resizer

autosizer.sh

#!/bin/bash
# Automatic Image file resizer
# Written by SirLagz
# Fixed and cleaned by Alek Ratzloff <alekratz@gmail.com>

if [[ ! $(whoami) =~ "root" ]]; then
    echo ""
    echo "**********************************"
    echo "*** This should be run as root ***"
    echo "**********************************"
    echo ""
    exit
fi

if [[ -z $1 ]]; then
    echo "Usage: $0 image.img"
    exit
fi

if [[ ! -e $1 || ! $(file $1) =~ "x86" ]]; then
    echo "Error : Not an image file, or file doesn't exist"
    exit
fi

partinfo=$(parted -m $1 unit B print)
partnumber=$(echo "$partinfo" | grep ext4 | awk -F: ' { print $1 } ')
partstart=$(echo "$partinfo" | grep ext4 | awk -F: ' { print substr($2,0,length($2)) } ')
loopback=$(losetup -f --show -o $partstart $1)
e2fsck -f $loopback
minsize=$(resize2fs -P $loopback | awk -F': ' ' { print $2 } ')
minsize=$(echo $minsize+1000 | bc)
resize2fs -p $loopback $minsize
sleep 1
losetup -d $loopback
partnewsize=$(echo "$minsize * 4096" | bc)
newpartend=$(echo "$partstart + $partnewsize" | bc)
part1=$(parted $1 rm $partnumber)
part2=$(parted $1 unit B mkpart primary $partstart $newpartend)
endresult=$(parted -m $1 unit B print free | tail -1 | awk -F: ' { print substr($2,0,length($2)-1) } ')
truncate -s $endresult $1