How to create a hard link to a file?

Question

linux

Script renames PHOTO1.JPG files to photo0001.jpg

#!bin/bash
rename ‘y/A-Z/a-z/‘ *.JPG
rename ‘s/photo/photo000/g’ *.jpg

How to make a hard link to Files PHOTO1.JPG, PHOTO2.JPG... PHOTO123.JPG
Renamed crookedly, you need to get photo0123.jpg from PHOTO123.JPG, but displays photo000123
How to fix it?

Answer 1

#!/bin/bash

for fn in *.JPG
do
    fn_small=${fn,,}
    num=${fn_small//[a-z.]}
    mv $fn ${fn_small/$num/$(printf "%04d" $num)}
done

Answer 2

horror, why did I do this ...
we generate a mountain of files for the test:

#!/bin/bash

for fname in PHOTO*;
do
    number=$(echo $fname | sed -r 's/PHOTO([0-9]+)\.JPG/\1/');
    echo $fname - $number;
    case $number in
        ?)
            newname='photo000'$number.jpg
            ;;
        ??)
            newname='photo00'$number.jpg
            ;;
        ???)
            newname='photo0'$number.jpg
            ;;
        ????)
            newname='photo'$number.jpg
            ;;
    esac
    echo "old: $fname new: $newname";
    # mv $fname $newname
done

Answer 3

Then like this
rename -e 's/\d+/sprintf("%04d",$&)/e' -- *.jpg