1. You may need fex2bin and bin2fex:
git clone git://github.com/linux-sunxi/sunxi-tools.git
With the using of ls, you can find the fex2bin and bin2fex.
2. Copy the script.bin from Android.
$mount -t vfat /dev/block/nanda /mnt/tmp
(Attention it's different from Linux.)
$adb pull /mnt/tmp/script.bin
3.Convert the script.bin to script.fex.
$chmod 777 script.bin
$./bin2fex script.bin > ./script.fex
Now, you can edit the script.fex.
Don't forget saving the file when you leave it.
4. Convert the script.fex to script.bin and push it back to the CB.
$./fex2bin script.fex > ./script.bin
$adb push script.bin /mnt/tmp
It will restart the CB. The new script.bin will come into effect.