bash rename files with prefix serial number - bash

Question

I have loads of files in a folder. I want to do two things:
prefix them with xxx three digit serial numbers - ascending: 001 002 and so on
remove the prefix from their names, so 001a.xyz = a.xyz
I intend to do this using a simple bash script. What's the most elegant and simple to understand way to do this?
edit
the files are on a removable device, and I cannot seem to set chmod +X on the script on the device. So how do I run a script from my home directory which will change the files in another directory?

Answer 1

To add prefixes:
counter=1
for f in *; do
printf -v prefix_str '%03d' "$((counter++))"
mv "$f" "${prefix_str}$f"
done
To remove prefixes (caution -- this may overwrite if you have two files with the same suffix but different prefixes):
for f in [0-9][0-9][0-9]*; do
mv "$f" "${f:3}"
done
Use mv -n to avoid overwriting when two files have the same suffix.

Answer 2

This should work:
#!/bin/bash
count=1
for file in *; do
if [[ $file =~ [0-9][0-9][0-9].* ]]; then
sfile="${file:3}"
new=$(printf "%03d" ${count})
mv "$file" "${new}${sfile}"
((count++))
else
new=$(printf "%03d" ${count})
mv "$file" "${new}${file}"
((count++))
fi
done
What this script does is, checks for a given file in the current directory. If the file has a prefix already it will remove it and assign a new sequential prefix. If the file has no prefix it will add a sequential prefix to it.
The end result should be, all the files in your current directory (some with and some without prefixes) will have a new sequential prefixes.